Manufacturing method of multilayer shell-core composite structural component

Abstract

A manufacturing method of a multilayer shell-core composite structural component comprises the following procedures: (1) respectively preparing feeding material for injection forming of a core layer, a buffer layer and a shell layer, wherein the powders of feeding material of the core layer and the shell layer are selected from one or more of metallic powder, ceramic powder or toughened ceramic powder, and are different from each other, and the powder of feeding material of the buffer layer is gradient composite material powder; (2) layer by layer producing the blank of multilayer shell-core composite structural component by powder injection molding; (3) degreasing the blank; and (4) sintering the blank to obtain the multilayer shell-core composite structural component. The multilayer shell-core composite structural component has the advantages of high surface hardness, abrasion resistance, uniform thickness of the shell layer, stable and persistent performance.

Claims

1. A method for manufacturing an acetabulum having a multilayer shell-core composite structure, comprising: preparing feedstocks of a shell layer, at least one transition layer and a core layer respectively; performing a powder injection molding with the feedstocks, to obtain a green body of the acetabulum comprising the shell layer, the at least one transition layer and the core layer; performing debinding on the green body of the acetabulum; and sintering the green body of the acetabulum after being debound, to obtain the acetabulum; wherein preparing a feedstock of each of the shell layer, the at least one transition layer and the core layer comprises: mixing a main powder of the each layer, a binder and an additive comprising a surface active agent and a plasticizer to obtain a mixture, where the main powder of the core layer is made of a powdered ceramic material, the main powder of the shell layer is made of a metal powder material or a powdered toughened ceramic material, and the main powder of the at least one transition layer comprises at least one mixed powder formed by mixing the main powder of the shell layer with the main powder of the core layer at a ratio, wherein the binder comprises polyoxymethylene resin; wherein preparing the feedstock of each of the shell layer, the at least one transition layer and the core layer further comprises: heating the mixture at a temperature greater than a melting point of the polyoxymethylene resin for a time period, so as to obtain a feedstock of polyaldehydes system having a solid content greater than 60 vol. %.

2. The method according to claim 1, wherein the powder injection molding with the feedstocks is performed at temperatures higher than a melting point of the polyoxymethylene resin and comprises a cooling duration.

3. The method according to claim 1, wherein the polyoxymethylene resin binder comprises 89 wt. % polyformaldehyde, 5 wt. % high density polyethylene and 6 wt. % other binding assistant agent.

4. The method according to claim 1, wherein the powdered ceramic material is selected from a group consisting of alumina, zirconia, titanium carbide, chromium carbide, silicon carbide, boron carbide, zirconium carbide, tantalum carbide, tungsten carbide, titanium nitride, chromium nitride, boron nitride, silicon nitride, zirconium nitride and tantalum nitride, or combinations thereof; the powdered toughened ceramic material is selected from a group consisting of cermet, ZrO.sub.2 toughened ceramic, whisker toughened ceramic and fiber toughened ceramic, or combinations thereof and the metal powder material is selected from a group consisting of niobium, zirconium, titanium, molybdenum, tantalum, cobalt, chromium, vanadium, aluminum and iron, or combinations thereof.

5. The method according to claim 1, wherein the main powder of the at least one transition layer comprises a plurality of mixed powders formed by mixing the main powder of the shell layer with the main powder of the core layer at different ratios to form multiple sub-layers of the at least one transition layer; and the multiple sub-layers are formed between the shell layer and the core layer, where the main powder of the shell layer takes up a main proportion in the main powders of some of the multiple sub-layers closer to the shell layer than to the core layer, and the main powder of the core layer takes up a main proportion in the main powders of the multiple sub-layers closer to the core layer than to the shell layer.

6. The method according to claim 5, wherein a feedstock of each of the multiple sub-layers of the at least one transition layer is prepared respectively, and green bodies of the multiple sub-layers are formed using the powder injection molding process respectively.

7. The method according to claim 1, wherein the method further comprises: performing surface finishing on the green body of the acetabulum prior to debinding.

8. The method according to claim 1, wherein each of the shell layer, the at least one transition layer and the core layer has a thickness ranging from about 0.1 mm to about 20 mm, and a relative density of more than 97%.

9. The method according to claim 1, wherein the main powder of the core layer is alumina powder and the main powder of the shell layer is Ti6A14V powder; and wherein the at least one transition layer comprises a first sub-layer closer to the shell layer and a second sub-layer closer to the core layer, the main powder of the first sub-layer is compound powder of Ti6A14V-20 vol. % Al.sub.2O.sub.3, and the main powder of the second sub-layer is compound powder of Ti6A14V-60 vol. % Al.sub.2O.sub.3.

10. The method according to claim 9, wherein, the powder injection molding is performed at a temperature ranging from about 170 C. to about 180 C., a pressure ranging from about 100 MPa to about 120 MPa, a dwell pressure ranging from about 70 MPa to about 85 MPa, and a cooling duration ranging from about 3 minutes to about 4 minutes.

11. The method according to claim 9, wherein the debinding on the green body comprises a catalytic debinding process, which is performed in an atmosphere furnace with a temperature ranging from about 110 C. to about 120 C., with hydrogen nitrate used as a debinding catalyst and nitrogen used as a debinding carrier gas, and with a debinding duration of 5 hours.

12. The method according to claim 9, wherein the green body is sintered in a controlled atmosphere Hot Isostatic Pressing (HIP) furnace, with a sintering temperature of about 1420 C., a pressure of about 40 MPa, and a soaking time of about 1 hour.

13. The method according to claim 9, wherein the alumina powder has a purity greater than 99.9 wt %, and a particle size ranging from 0.5 m to 5 m; and the Ti6A14V powder has a purity greater than 99.5 wt %, and a particle size ranging from 10 m to 35 m.

14. The method according to claim 9, wherein the feedstocks further comprise magnesium oxide powder added to the alumina powder as a sintering aid.

15. The method according to claim 1, wherein the debinding process comprises catalytic debinding, heating debinding, dissolution extraction debinding, supercritical fluid extraction (SFE) debinding or siphon debinding.

16. The method according to claim 1, wherein a Vickers-Hardness of a surface of the core layer is greater than 1950, and/or a fracture toughness of the shell layer is greater than 8 MPa.Math.m.sup.1/2.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 to FIG. 5 schematically illustrate several different cross-sectional views of artificial femoral ball heads having a multilayer shell-core composite structure according to a first and second embodiments of the present disclosure;

(2) FIG. 6 is schematically illustrates a flow chart of a manufacturing method of a multilayer shell-core structural component according to an embodiment of the present disclosure;

(3) FIG. 7 schematically illustrates a cross-sectional view of a femoral condyle prosthesis (prosthetic knees) having a multilayer shell-core composite structure according to a third embodiment of the present disclosure, where the drawing (a) is a side-view, and the drawing (b) is a front-view;

(4) FIG. 8 schematically illustrates a cross-sectional view of an artificial acetabulum having a multilayer shell-core composite structure according to a fourth embodiment of the present disclosure;

(5) FIG. 9 schematically illustrates a cross-sectional view of a plunger having a multilayer shell-core composite structure according to a fifth embodiment of the present disclosure; and

(6) FIG. 10 schematically illustrates a cross-sectional view of a ball valve body having a multilayer shell-core composite structure according to a sixth embodiment of the present disclosure, where the drawings on both sides show a bonnet respectively, and the drawing in the middle shows a valve body.

DETAILED DESCRIPTION

(7) Hereinafter, the disclosure will be described in detail with several embodiments in conjunction with the accompanying drawings.

First Embodiment

(8) A femoral ball head having a multilayer shell-core composite structure, is composed of a ceramic spherical shell layer 1 including high purity and superfine alumina, an alumina-based (niobium) cermet interlayer 5 (namely, transition layer), and a niobium metal core 2. The multilayer composite structure may have five different structures, which are illustrated in FIG. 1 to FIG. 5 and may be selected according to requirements of practical applications.

(9) Referring to FIG. 6, a method for manufacturing a femoral ball head having a multilayer shell-core composite structure in the first embodiment may include:

(10) (1) preparing feedstocks for powder injection molding which include high-purity and superfine alumina powder, alumina-based (niobium) cermet compound powder, and niobium metal powder. The high-purity and superfine alumina powder may have a purity greater than 99.9 wt %, have a particle size ranging from 0.5 m to 10 m. The niobium metal powder may have a purity greater than 99.8 wt %, have a particle size ranging from 0.5 m to 10 m. In order to decrease sintering temperature and improve sintering performance, magnesium oxide (MgO) powder with a concentration of 0.25 wt. % may be added into the high-purity and superfine alumina powder, and cobalt (Co) powder with a concentration of 3 wt. % may be added into the niobium metal powder, both of which may act as sintering aids. After preparation, the modified alumina powder, alumina-based (niobium) cermet compound powder and niobium metal powder are mixed with polyoxymethylene resin binder (89 wt. % polyformaldehyde, 5 wt. % high density polyethylene and 6 wt. % other binding assistant agent), respectively. The mixture is then mixed under a temperature of about 180 C. for about two and a half hours, so that a feedstock called as polyaldehydes system is obtained, which has a solid loading (solid content) greater than 55 vol. %.

(11) (2) by using three sets of moulds, performing injection molding successively to obtain the niobium metal core 2, the alumina-based (niobium) cermet interlayer 5, and the alumina spherical shell layer 1, of the femoral ball head having a multilayer shell-core composite structure including alumina ceramicalumina-based (niobium) cermet interlayerniobium metal. Firstly, feedstocks including niobium metal polyaldehydes are injected into a core mould (a first mould) to obtain the niobium metal core 2 having a bore-hole 3. Then, by using the niobium metal core 2 as an insert, a complex with the alumina-based (niobium) cermet interlayer 5 covering the niobium metal core 2 may be obtained through injection molding in a second mould. Then, by using the complex with the alumina-based (niobium) cermet interlayer 5 covering the niobium metal core 2 as an insert, a green body of the femoral ball head having a multilayer shell-core composite structure, which includes alumina ceramicalumina-based (niobium) cermet interlayerniobium metal, may be obtained through injection molding in a third mould. The temperature of the injection may be in a range from about 170 C. to about 180 C., the pressure of the injection may be in a range from about 110 MPa to about 130 MPa, the dwell pressure may be in a range from about 70 MPa to about 80 MPa, and the cooling time may be in a range from about 3 minutes to about 4 minutes.

(12) (3) if necessary, performing surface finishing on an alumina spherical shell surface 4 and the bore-hole 3 formed in the niobium metal core 2 of the green body of the femoral ball head having a multilayer shell-core composite structure, which includes alumina ceramicalumina-based (niobium) cermet interlayerniobium metal.

(13) (4) performing catalytic debinding on the green body of the femoral ball head having a multilayer shell-core composite structure including alumina ceramicalumina-based (niobium) cermet interlayerniobium metal in an atmosphere furnace with a temperature ranging from about 110 C. to about 120 C., where hydrogen nitrate is used as debinding catalyst, nitrogen is used as debinding carrier gas, and the catalytic debinding process may last for about 5 hours.

(14) (5) after being catalytic debound, sintering the green body of the femoral ball head having a multilayer shell-core composite structure including alumina ceramicalumina (niobium) transition layerniobium metal in a controlled atmosphere Hot Isostatic Pressing (HIP) furnace, where the sintering is performed at a temperature of about 1450 C., a pressure of about 35 MPa, and the soaking time is about 1 hour, so that an alumina spherical shell layer 1 which has a relative density greater than 99% and a hardness greater than HV1950, an alumina (niobium) transition layer 5 which becomes densification and toughness and the niobium metal core 2, may be obtained.

(15) (6) according to size requirements of the products, performing micro-machining on the alumina ceramic spherical shell surface 4 and the bore-hole 3 of the sintering body of the femoral ball head having a multilayer shell-core composite structure, which includes alumina ceramicalumina-based (niobium) cermet interlayerniobium metal.

(16) (7) finally, polishing the alumina ceramic spherical shell surface 4 by using SiC ultrafine powder and diamond abrasive paste, to obtain the femoral ball head having a multilayer shell-core composite structure including alumina ceramic-alumina-based (niobium) cermet interlayerniobium metal, so that a smooth finished surface, and a proper dimensional coordination between the bore-hole 3 and the femoral component may be obtained.

Second Embodiment

(17) A femoral ball head having a multilayer shell-core composite structure, includes a ceramic spherical shell layer 1 including high purity and superfine alumina, a toughened ceramic interlayer 5 of ZrO.sub.2(3Y.sub.2O.sub.3)-80 wt. % Al.sub.2O.sub.3 and a toughened ceramic core 2 of ZrO.sub.2(3Y.sub.2O.sub.3)-20 wt. % Al.sub.2O.sub.3.

(18) Referring to FIG. 6, a method for manufacturing a femoral ball head having a multilayer shell-core composite structure in the second embodiment may include:

(19) (1) preparing feedstocks for powder injection molding which include high-purity and superfine alumina powder, and compound powder of ZrO.sub.2 (3Y.sub.2O.sub.3)-80 wt. % Al.sub.2O.sub.3 and compound powder of ZrO.sub.2(3Y.sub.2O.sub.3)-20 wt. % Al.sub.2O.sub.3. The high-purity and superfine alumina powder may have a purity greater than 99.9 wt %, and a particle size ranging from 0.5 m to 10 m. The ZrO.sub.2 powder may have a purity greater than 99.8 wt %, and a particle size ranging from 0.5 m to 10 m. In order to decrease sintering temperature and improve sintering performance, magnesium oxide (MgO) powder with a concentration of 0.25 wt. % may be added into the high-purity and superfine alumina powder as sintering aids. After preparation, the modified alumina powder, compound powder of ZrO.sub.2(3Y.sub.2O.sub.3)-80 wt. % Al.sub.2O.sub.3 and compound powder of ZrO.sub.2(3Y.sub.2O.sub.3)-20 wt. % Al.sub.2O.sub.3 are mixed with polyoxymethylene resin binder (89 wt. % polyformaldehyde, 5 wt. % high density polyethylene and 6 wt. % other binding assistant agent), respectively. The mixture is then mixed under a temperature of about 180 C. for about two and a half hours, so that a feedstock of polyaldehydes system, having a solid loading (solid content) greater than 55 vol. %, can be obtained.

(20) (2) by using three sets of moulds, performing injection molding successively to obtain the core 2 of ZrO.sub.2(3Y.sub.2O.sub.3)-20 wt. % Al.sub.2O.sub.3, the interlayer 5 of ZrO.sub.2(3Y.sub.2O.sub.3)-80 wt. % Al.sub.2O.sub.3, and the alumina spherical shell layer 1 of the femoral ball head having a multilayer shell-core composite structure including alumina ceramicinterlayer of ZrO.sub.2(3Y.sub.2O.sub.3)-80 wt. % Al.sub.2O.sub.3core of ZrO.sub.2(3Y.sub.2O.sub.3)-20 wt. % Al.sub.2O.sub.3. Firstly, feedstocks including ZrO.sub.2(3Y.sub.2O.sub.3)-20 wt. % Al.sub.2O.sub.3 polyaldehydes are injected into a core mould (a first mould) to obtain the core 2 of ZrO.sub.2(3Y.sub.2O.sub.3)-20 wt. % Al.sub.2O.sub.3 having a bore-hole 3. Then, by using the core 2 of ZrO.sub.2(3Y.sub.2O.sub.3)-20 wt. % Al.sub.2O.sub.3 as an insert, a complex with the interlayer 5 of ZrO.sub.2(3Y.sub.2O.sub.3)-80 wt. % Al.sub.2O.sub.3 covering the core 2 of ZrO.sub.2(3Y.sub.2O.sub.3)-20 wt. % Al.sub.2O.sub.3 may be obtained through injection molding in a second mould. Then, using the complex with the interlayer 5 of ZrO.sub.2(3Y.sub.2O.sub.3)-80 wt. % Al.sub.2O.sub.3 covering the core 2 of ZrO.sub.2(3Y.sub.2O.sub.3)-20 wt. % Al.sub.2O.sub.3 as an insert, a green body of the femoral ball head having a multilayer shell-core composite structure including alumina ceramicinterlayer of ZrO.sub.2(3Y.sub.2O.sub.3)-80 wt. % Al.sub.2O.sub.3core of ZrO.sub.2(3Y.sub.2O.sub.3)-20 wt. % Al.sub.2O.sub.3, may be obtained through injection molding in a third mould. The temperature of the injection may be in a range from about 170 C. to about 180 C., the pressure of the injection may be in a range from about 110 MPa to about 130 MPa, the dwell pressure may be in a range from about 70 MPa to about 80 MPa, and the cooling time may be in a range from about 3 minutes to about 4 minutes.

(21) (3) if necessary, performing surface finishing on an alumina spherical shell surface 4 and the bore-hole 3 formed in the core 2 of ZrO.sub.2(3Y.sub.2O.sub.3)-20 wt. % Al.sub.2O.sub.3 of the green body of the femoral ball head having a multilayer shell-core composite structure including alumina ceramicinterlayer of ZrO.sub.2(3Y.sub.2O.sub.3)-80 wt. % Al.sub.2O.sub.3core of ZrO.sub.2(3Y.sub.2O.sub.3)-20 wt. % Al.sub.2O.sub.3.

(22) (4) performing catalytic debinding on the green body of the femoral ball head having a multilayer shell-core composite structure including alumina ceramicinterlayer of ZrO.sub.2(3Y.sub.2O.sub.3)-80 wt. % Al.sub.2O.sub.3core of ZrO.sub.2(3Y.sub.2O.sub.3)-20 wt. % Al.sub.2O.sub.3 in an atmosphere furnace with a temperature ranging from about 110 C. to about 120 C., where hydrogen nitrate is used as debinding catalyst, nitrogen is used as debinding carrier gas, and the catalytic debinding may last for about 5 hours.

(23) (5) after being catalytic debound, sintering the green body of the femoral ball head having a multilayer shell-core composite structure including alumina ceramicinterlayer of ZrO.sub.2(3Y.sub.2O.sub.3)-80 wt. % Al.sub.2O.sub.3core of ZrO.sub.2(3Y.sub.2O.sub.3)-20 wt. % Al.sub.2O.sub.3 in an air furnace, where the sintering may be performed at a temperature of about 1600 C., and the soaking time is about 1 hour, so that an alumina spherical shell layer 1 which has a relative density greater than 99%, a hardness greater than HV1950, an interlayer 5 of ZrO.sub.2(3Y.sub.2O.sub.3)-80 wt. % Al.sub.2O.sub.3 which is densified and toughed and a core 2 of ZrO.sub.2(3Y.sub.2O.sub.3)-20 wt. % Al.sub.2O.sub.3 which has a fracture toughness greater than 10 MPa.Math.m.sup.1/2, may be obtained.

(24) (6) according to size requirements of the products, performing micro-machining on the alumina ceramic spherical shell surface 4 and the bore-hole 3 of the sintering body of the femoral ball head having a multilayer shell-core composite structure including alumina ceramicinterlayer of ZrO.sub.2(3Y.sub.2O.sub.3)-80 wt. % Al.sub.2O.sub.3core of ZrO.sub.2(3Y.sub.2O.sub.3)-20 wt. % Al.sub.2O.sub.3.

(25) (7) finally, polishing the alumina ceramic spherical shell surface 4 by using SiC ultrafine powder and diamond abrasive paste, to obtain the femoral ball head having a multilayer shell-core composite structure including alumina ceramicinterlayer of ZrO.sub.2(3Y.sub.2O.sub.3)-80 wt. % Al.sub.2O.sub.3core of ZrO.sub.2(3Y.sub.2O.sub.3)-20 wt. % Al.sub.2O.sub.3, which has a smooth finished surface, and a proper dimensional coordination between the bore-hole 3 and the femoral component.

Third Embodiment

(26) Referring to FIG. 7, a femoral condyle prosthesis (one component of an artificial knee-joint) having a multilayer shell-core composite structure, includes a Ti6Al4V core layer 11, a transition layer 12 of Ti6Al4V-20 vol. % Al.sub.2O.sub.3, a transition layer 13 of Ti6Al4V-60 vol. % Al.sub.2O.sub.3, and a high-purity and superfine ceramic shell layer 14.

(27) Referring to FIG. 6, a method for manufacturing a femoral condyle prosthesis having a multilayer shell-core composite structure in the third embodiment may include:

(28) (1) preparing feedstocks for powder injection molding which include high-purity and superfine alumina powder, compound powder of Ti6Al4V-60 vol. % Al.sub.2O.sub.3, compound powder of Ti6Al4V-20 vol. % Al.sub.2O.sub.3, and Ti6Al4V powder. The high-purity and superfine alumina powder may have a purity greater than 99.9 wt %, have a particle size ranging from 0.5 m to 5 m. The Ti6Al4V powder may have a purity greater than 99.5 wt %, have a particle size ranging from 10 m to 35 m. In order to decrease sintering temperature and improve sintering performance, magnesium oxide (MgO) powder with a concentration of 0.1 wt. % may be added into the high-purity and superfine alumina powder as sintering aids. After preparation, the modified alumina powder, compound powder of Ti6Al4V-60 vol. % Al.sub.2O.sub.3, compound powder of Ti6Al4V-20 vol. % Al.sub.2O.sub.3, and Ti6Al4V powder are mixed with polyoxymethylene resin binder (89 wt. % polyformaldehyde, 5 wt. % high density polyethylene and 6 wt. % other binding assistant agent), respectively. The mixture is then mixed under a temperature of about 180 C. for about two and a half hours, so that a feedstock of a polyaldehydes system is obtained, which has a solid loading (solid content) greater than 60 vol. %.

(29) (2) by using four sets of moulds, performing co-injection molding successively to obtain the Ti6Al4V core layer 11, the transition layer 12 of Ti6Al4V-20 wt. % Al.sub.2O.sub.3, the transition layer 13 of Ti6Al4V-80 wt. % Al.sub.2O.sub.3 and the high-purity and superfine alumina ceramic shell layer 14 of the femoral condyle prosthesis having a multilayer shell-core composite structure. Firstly, feedstocks including Ti6Al4V polyaldehydes are injected into a first mould to obtain the Ti6Al4V core layer 11 of the femoral condyle prosthesis. Then, by using the Ti6Al4V core layer 11 as an insert, a complex with the transition layer 12 of Ti6Al4V-20 wt. % Al.sub.2O.sub.3 covering the Ti6Al4V core layer 11 may be obtained through injection molding in a second mould. Then, by using the complex of the transition layer 12 of Ti6Al4V-20 wt. % Al.sub.2O.sub.3/the Ti6Al4V core layer 11 as an insert, a compound covered by the transition layer 13 of Ti6Al4V-80 wt. % Al.sub.2O.sub.3 may be obtained through injection molding in a third mould. Then, by using the complex of the transition layer 13 of Ti6Al4V-80 wt. % Al.sub.2O.sub.3/the transition layer 12 of Ti6Al4V-20 wt. % Al.sub.2O.sub.3/the Ti6Al4V core layer 11 as an insert, a green body of the femoral condyle prosthesis having a multilayer shell-core composite structure which is covered by the high-purity and superfine Al.sub.2O.sub.3 ceramic shell layer 14, may be obtained through injection molding in a fourth mould. The temperature of the injection may be in a range from about 170 C. to about 180 C., the pressure of the injection may be in a range from about 100 MPa to about 120 MPa, the dwell pressure may be in a range from about 70 MPa to about 85 MPa, and the cooling time may be in a range from about 3 minutes to about 4 minutes.

(30) (3) if necessary, performing surface finishing on the alumina shell layer 14 and the Ti6Al4V core layer 11 of the green body of the femoral condyle prosthesis having a multilayer shell-core composite structure.

(31) (4) performing catalytic debinding on the green body of the femoral condyle prosthesis having a multilayer shell-core composite structure in an atmosphere furnace with a temperature ranging from about 110 C. to about 120 C., where hydrogen nitrate is used as debinding catalyst, nitrogen is used as debinding carrier gas, and the catalytic debinding may last for about 5 hours.

(32) (5) after being catalytic debound, sintering the green body of the femoral condyle prosthesis having a multilayer shell-core composite structure in a controlled atmosphere Hot Isostatic Pressing (HIP) furnace, where the sintering may be performed at a temperature of about 1420 C., a pressure of about 40 MPa, and the soaking time is about 1 hour, so that an alumina shell layer 4 which has a relative density greater than 99.5% and a hardness greater than HV1950, densified and toughed transition layers 12 and 13, and a Ti6Al4V core layer 11 which has a high fracture toughness and has a relative density greater than 99.0%, may be obtained.

(33) (6) according to size requirements of the products, performing micro-machining on the alumina shell layer 14 of the sintering body of the femoral condyle prosthesis having a multilayer shell-core composite structure.

(34) (7) then, polishing the alumina shell layer 14 by using SiC ultrafine powder and diamond abrasive paste, to obtain the femoral condyle prosthesis having a multilayer shell-core composite structure, which has a smooth finished surface.

Fourth Embodiment

(35) Referring to FIG. 8, an acetabulum (one component of an artificial hip joint) having a multilayer shell-core composite structure, includes a high-purity and superfine Al.sub.2O.sub.3 ceramic core layer 21, a transition layer 22 of Ti6Al4V-60 vol. % Al.sub.2O.sub.3, a transition layer 23 of Ti6Al4V-20 vol. % Al.sub.2O.sub.3, and a Ti6Al4V shell layer 24.

(36) Referring to FIG. 6, a method for manufacturing an acetabulum having a multilayer shell-core composite structure in the fourth embodiment may include:

(37) (1) preparing feedstocks for powder injection molding which include high-purity and superfine alumina powder, compound powder of Ti6Al4V-60 vol. % Al.sub.2O.sub.3, compound powder of Ti6Al4V-20 vol. % Al.sub.2O.sub.3, and Ti6Al4V powder. The high-purity and superfine alumina powder may have a purity greater than 99.9 wt %, have a particle size ranging from 0.5 m to 5 m. The Ti6Al4V powder may have a purity greater than 99.5 wt %, have a particle size ranging from 10 m to 35 m. In order to decrease sintering temperature and improve sintering performance, magnesium oxide (MgO) powder with a concentration of 0.1 wt. % may be added into the high-purity and superfine alumina powder as sintering aids. After preparation, the modified alumina powder, compound powder of Ti6Al4V-60 vol. % Al.sub.2O.sub.3, compound powder of Ti6Al4V-20 vol. % Al.sub.2O.sub.3, and Ti6Al4V powder are mixed with polyoxymethylene resin binder (89 wt. % polyformaldehyde, 5 wt. % high density polyethylene and 6 wt. % other binding assistant agent), respectively. The mixture is then mixed under a temperature of about 180 C. for about two and a half hours, so that a polyaldehydes system is obtained, which has a solid loading (solid content) greater than 60 vol. %.

(38) (2) by using four sets of moulds, performing co-injection molding successively to obtain the high-purity and superfine Al.sub.2O.sub.3 ceramic core layer 21, the transition layer 22 of Ti6Al4V-60 vol. % Al.sub.2O.sub.3, the transition layer 23 of Ti6Al4V-20 vol. % Al.sub.2O.sub.3 and the Ti6Al4V shell layer 24 of the acetabulum having a multilayer shell-core composite structure. Firstly, feedstocks including Ti6Al4V polyaldehydes are injected into a first mould to obtain the Ti6Al4V shell layer 24. Then, by using the Ti6Al4V shell layer 24 as an inserts, a complex with the transition layer 23 of Ti6Al4V-20 wt. % Al.sub.2O.sub.3 covering the Ti6Al4V shell layer 24 may be obtained through injection molding in a second mould. Then, by using the complex of the transition layer 23 of Ti6Al4V-20 wt. % Al.sub.2O.sub.3/the Ti6Al4V shell layer 24 as an inserts, a complex covered by the transition layer 22 of Ti6Al4V-80 wt. % Al.sub.2O.sub.3 may be obtained through injection molding in a third mould. Then, by using the complex of the transition layer 22 of Ti6Al4V-80 wt. % Al.sub.2O.sub.3/the transition layer 23 of Ti6Al4V-20 wt. % Al.sub.2O.sub.3/the Ti6Al4V shell layer 24 as an inserts, a green body of the acetabulum having a multilayer shell-core composite structure which is covered by the high-purity and superfine Al.sub.2O.sub.3 ceramic core layer 21, may be obtained through injection molding in a fourth mould. The temperature of the injection may be in a range from about 170 C. to about 180 C., the pressure of the injection may be in a range from about 100 MPa to about 120 MPa, the dwell pressure may be in a range from about 70 MPa to about 85 MPa, and the cooling time may be in a range from about 3 minutes to about 4 minutes.

(39) (3) if necessary, performing surface finishing on the Al.sub.2O.sub.3 ceramic core layer 1 and the Ti6Al4V shell layer 24 of the green body of the acetabulum having a multilayer shell-core composite structure.

(40) (4) performing catalytic debinding on the green body of the acetabulum having a multilayer shell-core composite structure in an atmosphere furnace with a temperature ranging from about 110 C. to about 120 C., where hydrogen nitrate is used as debinding catalyst, nitrogen is used as debinding carrier gas, and the catalytic debinding may last for about 5 hours.

(41) (5) after being catalytic debound, sintering the green body of the acetabulum having a multilayer shell-core composite structure in a controlled atmosphere Hot Isostatic Pressing (HIP) furnace, where the sintering may be performed at a temperature of about 1420 C., a pressure of about 40 MPa, and the soaking time is about 1 hour, so that an alumina core layer 21 which has a relative density greater than 99.5% and a hardness greater than HV1950, transition layers 22 and 23 which are densified and toughed, and a Ti6Al4V shell layer 24 which has a high fracture toughness and has a relative density greater than 99.0%, may be obtained.

(42) (6) according to size requirements of the products, performing micro-machining on a surface of the alumina core layer 21 of the sintering body of the acetabulum having a multilayer shell-core composite structure.

(43) (7) then, polishing a surface of the alumina core layer 21 by using SiC ultrafine powder and diamond abrasive paste, to obtain the acetabulum having a multilayer shell-core composite structure, which has a smooth finished surface, and a proper dimensional coordination with a femoral ball head.

Fifth Embodiment

(44) Referring to FIG. 9, a plunger having a multilayer shell-core composite structure, is composed of a ZrO.sub.2(Y+Ce) shell layer 31, a second transition layer 32 of 17-4PH stainless steel 60 vol. % ZrO.sub.2(Y+Ce), a first transition layer 33 of 17-4PH stainless steel 30 vol. % ZrO.sub.2(Y+Ce), and a 17-4PH stainless steel core spindle 34.

(45) Referring to FIG. 6 in conjunction with FIG. 9, a method for manufacturing a ceramic plunger having a multilayer shell-core composite structure in the fifth embodiment may include:

(46) (1) preparing feedstocks for powder injection molding which include ZrO.sub.2(Y+Ce) powder, compound powder of 17-4PH stainless steel 60 vol. % ZrO.sub.2(Y+Ce), compound powder of 17-4PH stainless steel 30 vol. % ZrO.sub.2(Y+Ce), and 17-4PH stainless steel powder. The ZrO.sub.2 powder may have a purity greater than 98.5 wt %, have a particle size ranging from 0.2 m to 0.5 m. The 17-4PH stainless steel powder may have a purity greater than 98.8 wt %, have a particle size ranging from 5 m to 25 m. In order to ensure performance, 1.5% mol Y.sub.2O.sub.3 powder and 4% mol CeO.sub.2 powder may be added into the ZrO.sub.2 powder as stabilizing additive, to obtain partially stabilized ZrO.sub.2(Y+Ce)powder. After preparation, the modified ZrO.sub.2(Y+Ce) powder, compound powder of 17-4PH stainless steel 60 vol. % ZrO.sub.2 ((Y+Ce), compound powder of 17-4PH stainless steel 30 vol. % ZrO.sub.2(Y+Ce), and 17-4PH stainless steel powder are mixed with polyoxymethylene resin binder (89 wt. % polyformaldehyde, 5 wt. % high density polyethylene and 6 wt. % other binding assistant agent), respectively. The mixture is then mixed under a temperature of about 180 C. for about two and a half hours, so that a polyaldehydes system is obtained, which has a solid loading (solid content) greater than 55 vol. %.

(47) (2) by using four sets of moulds, performing co-injection molding successively to obtain the ZrO.sub.2(Y+Ce) shell layer 31, the second transition layer 32 of 17-4PH stainless steel 60 vol. % ZrO.sub.2(Y+Ce), the first transition layer 33 of 17-4PH stainless steel 30 vol. % ZrO.sub.2(Y+Ce), and the 17-4PH stainless steel core spindle 34 of the ceramic plunger having a multilayer shell-core composite structure. Firstly, feedstocks including 17-4PH stainless steel polyaldehydes are injected into a chamber 61a in a first mould to obtain the 17-4PH stainless steel core spindle 34 of the ceramic plunger. Then, by using the stainless steel core spindle 34 as a first insertion, a first complex with the first transition layer 33 of 17-4PH stainless steel 30 vol. % ZrO.sub.2(Y+Ce) covering the stainless steel core spindle 34 may be obtained through injection molding in a first space between the first insertion and a second mould. Then, by using the first complex of the first transition layer 33 of 17-4PH stainless steel 30 vol. % ZrO.sub.2(Y+Ce)/the stainless steel core spindle 34 as a second insertion, a second complex covered by the second transition layer 32 of 17-4PH stainless steel 60 vol. % ZrO.sub.2(Y+Ce) may be obtained through injection molding in a second space between the second insertion and a third mould. At last, by using the second complex of the second transition layer 32 of 17-4PH stainless steel 60 vol. % ZrO.sub.2(Y+Ce)/the first transition layer 33 of 17-4PH stainless steel 30 vol. % ZrO.sub.2(Y+Ce)/the stainless steel core spindle 34 as a third insertion, a green body of the ceramic plunger having a multilayer shell-core composite structure which is covered by the superfine ZrO.sub.2(Y+Ce) ceramic shell layer 31, may be obtained through injection molding in a third space between the third insertion and a fourth mould. The temperature of the injection may be in a range from about 170 C. to about 180 C., the pressure of the injection may be in a range from about 100 MPa to about 120 MPa, the dwell pressure may be in a range from about 70 MPa to about 85 MPa, and the cooling time may be in a range from about 3 minutes to about 4 minutes.

(48) (3) if necessary, performing surface finishing on the ZrO.sub.2(Y+Ce) shell layer 31 and the 17-4PH stainless steel core spindle 34 of the green body of the ceramic plunger having a multilayer shell-core composite structure.

(49) (4) performing catalytic debinding on the green body of the ceramic plunger having a multilayer shell-core composite structure in an atmosphere furnace with a temperature ranging from about 110 C. to about 120 C., where hydrogen nitrate is used as debinding catalyst, nitrogen is used as debinding carrier gas, and the catalytic debinding may last for about 5 hours.

(50) (5) after being catalytic debound, sintering the green body of the ceramic plunger having a multilayer shell-core composite structure in a controlled atmosphere Hot Isostatic Pressing (HIP) furnace, where the sintering may be performed at a temperature of about 1350 C., a pressure of about 35 MPa, and the soaking time is about 1 hour, so that a ZrO.sub.2 shell layer 31 which has a relative density greater than 98.8% and a hardness greater than HV1500, transition layers 32 and 33 which are densified and toughed, and a 17-4PH stainless steel core spindle 4, may be obtained.

(51) (6) according to size requirements of the products, performing micro-machining on a surface of the ZrO.sub.2(Y+Ce) shell layer 31, and performing machining on both ends of the 17-4PH stainless steel core spindle 34.

(52) (7) finally, polishing a surface of the ZrO.sub.2(Y+Ce) shell layer 31 by using SiC ultrafine powder and diamond abrasive paste, to obtain the ceramic plunger having a multilayer shell-core composite structure, which has a smooth finished surface, and a proper dimensional coordination with a mantle of the ceramic plunger.

Sixth Embodiment

(53) Referring to FIG. 10, a fully padded ceramic ball valve body (including one valve body and two bonnets) having a multilayer shell-core composite structure, is composed of a ZrO.sub.2(Y+Ce) valve liner 41, a transition layer 42 of 17-4PH stainless steel 60 vol. % ZrO.sub.2(Y+Ce), a transition layer 43 of 17-4PH stainless steel 30 vol. % ZrO.sub.2(Y+Ce), and a 17-4PH stainless steel valve shell 44.

(54) Referring to FIG. 6, a method for manufacturing a fully padded ceramic ball valve body having a multilayer shell-core composite structure in the sixth embodiment may include:

(55) (1) preparing feedstocks for powder injection molding which include ZrO.sub.2(Y+Ce) powder, compound powder of 17-4PH stainless steel 60 vol. % ZrO.sub.2(Y+Ce), compound powder of 17-4PH stainless steel 30 vol. % ZrO.sub.2(Y+Ce), and 17-4PH stainless steel powder. The ZrO.sub.2 powder may have a purity greater than 98.5 wt %, have a particle size ranging from 0.2 m to 1.5 m. The 17-4PH stainless steel powder may have a purity greater than 98.8 wt %, have a particle size ranging from 5 m to 35 m. In order to improve performance, 1.5% mol Y.sub.2O.sub.3 powder and 4% mol CeO.sub.2 powder may be added into the ZrO.sub.2 powder as stabilizing additive, to obtain partially stabilized ZrO.sub.2(Y+Ce)powder. After preparation, the modified ZrO.sub.2(Y+Ce) powder, compound powder of 17-4PH stainless steel 60 vol. % ZrO.sub.2(Y+Ce), compound powder of 17-4PH stainless steel 30 vol. % ZrO.sub.2(Y+Ce), and 17-4PH stainless steel powder are mixed with polyoxymethylene resin binder (89 wt. % polyformaldehyde, 5 wt. % high density polyethylene and 6 wt. % other binding assistant agent), respectively. The mixture is then mixed under a temperature of about 180 C. for about two and a half hours, so that a polyaldehydes system is obtained, which has a solid loading (solid content) greater than 55 vol. %.

(56) (2) by using four sets of moulds, performing co-injection molding successively to obtain the ZrO.sub.2(Y+Ce) valve liner 41, the transition layer 42 of 17-4PH stainless steel 60 vol. % ZrO.sub.2(Y+Ce), the transition layer 43 of 17-4PH stainless steel 30 vol. % ZrO.sub.2(Y+Ce), and the 17-4PH stainless steel valve shell 44 of the fully padded ceramic ball valve body having a multilayer shell-core composite structure. Firstly, feedstocks including 17-4PH stainless steel polyaldehydes are injected into a first mould to obtain the 17-4PH stainless steel valve shell 44. Then, by using the stainless steel valve shell 44 as an inserts, a complex with the transition layer 43 of 17-4PH stainless steel 30 vol. % ZrO.sub.2(Y+Ce) covering the stainless steel valve shell 44 may be obtained through injection molding in a second mould. Then, by using the complex of the transition layer 43 of 17-4PH stainless steel 30 vol. % ZrO.sub.2(Y+Ce)/the stainless steel valve shell 44 as an inserts, a complex covered by the transition layer 42 of 17-4PH stainless steel 60 vol. % ZrO.sub.2(Y+Ce) may be obtained through injection molding in a third mould. At last, by using the complex of the transition layer 42 of 17-4PH stainless steel 60 vol. % ZrO.sub.2(Y+Ce)/the transition layer 43 of 17-4PH stainless steel 30 vol. % ZrO.sub.2(Y+Ce)/the stainless steel valve shell 44 as an inserts, a green body of the fully padded ceramic ball valve body having a multilayer shell-core composite structure which is covered by the superfine ZrO.sub.2(Y+Ce) valve liner 41, may be obtained through injection molding in a fourth mould. The temperature of the injection may be in a range from about 170 C. to about 180 C., the pressure of the injection may be in a range from about 100 MPa to about 120 MPa, the dwell pressure may be in a range from about 70 MPa to about 85 MPa, and the cooling time may be in a range from about 3 minutes to about 4 minutes.

(57) (3) if necessary, performing surface finishing on the ZrO.sub.2(Y+Ce) valve liner 41 and the 17-4PH stainless steel valve shell 44 of the green body of the fully padded ceramic ball valve body having a multilayer shell-core composite structure.

(58) (4) performing catalytic debinding on the green body of the fully padded ceramic ball valve body having a multilayer shell-core composite structure in an atmosphere furnace with a temperature ranging from about 110 C. to about 120 C., where hydrogen nitrate is used as debinding catalyst, nitrogen is used as debinding carrier gas, and the catalytic debinding may last for about 5 hours.

(59) (5) after being catalytic debound, sintering the green body of the fully padded ceramic ball valve body having a multilayer shell-core composite structure in a controlled atmosphere Hot Isostatic Pressing (HIP) furnace, where the sintering may be performed at a temperature of about 1350 C., a pressure of about 35 MPa, and the soaking time is about 1 hour, so that a ZrO.sub.2(Y+Ce) valve liner 41 which has a relative density greater than 98.8% and a hardness greater than HV1450, densified and toughed transition layers 42 and 43, and a 17-4PH stainless steel valve shell 44, may be obtained.

(60) (6) according to size requirements of the products, performing micro-machining on a surface of the ZrO.sub.2(Y+Ce) valve liner 41, and if necessary, performing machining on the 17-4PH stainless valve shell 44.

(61) (7) finally, polishing a surface of the ZrO.sub.2(Y+Ce) valve liner 41 by using SiC ultrafine powder and diamond abrasive paste, especially a round surface of the ZrO.sub.2(Y+Ce) valve liner 41 of two bonnets, so as to obtain the fully padded ceramic ball valve body having a multilayer shell-core composite structure, which has a smooth finished surface, and a proper dimensional coordination with a valve spool of the ceramic ball valve.

(62) Although the present disclosure has been disclosed above with reference to preferred embodiments thereof, it should be understood that the disclosure is presented by way of example only, and not limitation. Those skilled in the art can modify and vary the embodiments without departing from the spirit and scope of the present disclosure.