Wolfram carbide based hard alloy and its preparation method

Abstract

A wolfram carbide based hard alloy includes a wolfram carbide base having a first binder. A plurality of hard particles with different sizes are dispersed in the wolfram carbide base, and hardness of the hard particles is larger than hardness of the wolfram carbide base.

Claims

1. A wolfram carbide based hard alloy, comprising a wolfram carbide base including a first binder, wherein a plurality of hard particles with different sizes are dispersed in the wolfram carbide base, the hardness of the hard particles is larger than the hardness of the wolfram carbide base; wherein, the hard particles comprise first hard particles having a first hardness and a first size and second hard particles having a second hardness and a second size; wherein, the first hard particles and the second hard particles are prepared by hot-pressing and sintering unit granules having a layer of a matrix slurry on the surface, wherein the matrix slurry comprises uniformly mixed tungsten carbide powder and cobalt; in the alloy, a weight percentage of the wolfram carbide base is in a range from 10% to 30%; a weight percentage of the first hard particles is in a range from 18% to 24%; and a weight percentage of the second hard particles is in a range from 52% to 66%.

2. The alloy according to claim 1, wherein a ratio of the first size to the second size is in a range from 1:5 to 1:7.

3. The alloy according to claim 2, wherein the hardness of the first hard particles is larger than the hardness of the second hard particles.

4. The alloy according to claim 2, wherein the first hard particles comprise wolfram carbide and a second binder, and the second hard particles comprise wolfram carbide and a third binder, wherein a weight percentage of the first binder in the wolfram carbide base is larger than a weight percentage of the second binder in the first hard particles, and the weight percentage of the second binder in the first hard particles is larger than a weight percentage of the third binder in the second hard particles; wherein the first binder, the second binder, and the third binder are all cobalt; wherein a weight percentage of cobalt in the wolfram carbide base is in a range from 7% to 40%; a weight percentage of cobalt in the first hard particles is in a range from 6% to 13%; and a weight percentage of cobalt in the second hard particles is in a range from 5% to 12%.

5. The alloy according to claim 3, wherein the first hard particles comprise wolfram carbide and a second binder, and the second hard particles comprise wolfram carbide and a third binder, wherein a weight percentage of the first binder in the wolfram carbide base is larger than a weight percentage of the second binder in the first hard particles, and the weight percentage of the second binder in the first hard particles is larger than a weight percentage of the third binder in the second hard particles; wherein the first binder, the second binder, and the third binder are all cobalt; wherein a weight percentage of cobalt in the wolfram carbide base is in a range from 7% to 40%; a weight percentage of cobalt in the first hard particles is in a range from 6% to 13%; and a weight percentage of cobalt in the second hard particles is in a range from 5% to 12%.

6. The alloy according to claim 4, wherein the weight percentage of cobalt in the wolfram carbide base is in a range from 10% to 20%; the weight percentage of cobalt in the first hard particles is in a range from 8% to 13%; and the weight percentage of cobalt in the second hard particles is in a range from 5% to 10%.

7. The alloy according to claim 5, wherein, the weight percentage of cobalt in the wolfram carbide base is in a range from 10% to 20%; the weight percentage of cobalt in the first hard particles is in a range from 8% to 13%; and the weight percentage of cobalt in the second hard particles is in a range from 5% to 10%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present disclosure will be described in a more detailed way below based on embodiments and with reference to the accompanying drawings. In the drawings:

(2) FIG. 1 shows a photomicrograph of a first sample D# of a wolfram carbide based hard alloy according to the present disclosure;

(3) FIG. 2 shows a photomicrograph of a second sample H# of a wolfram carbide based hard alloy according to the present disclosure; and

(4) FIG. 3 shows a photomicrograph of a third sample L# of a wolfram carbide based hard alloy according to the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(5) The present disclosure is further explained with reference to the accompanying drawings hereinafter.

Embodiment 1

(6) First particles are prepared. WC powder and Co powder are mixed uniformly with a weight ratio of 90:10 and then are sintered at a temperature of 1400° C. After a sintered product is crushed and sieved, the first particles having a size in a range from 10 μm to 20 μm are obtained.

(7) Second particles are prepared. WC powder and Co powder are mixed uniformly with a weight ratio of 94:6 and then are sintered at a temperature of 1400° C. After a sintered product is crushed and sieved, the second particles having a size in a range from 70 μm to 120 μm are obtained.

(8) Base slurry is prepared. WC powder and Co powder are mixed uniformly with a weight ratio of 4:1, and the base slurry is obtained.

(9) The first particles and the second particles are poured into the base slurry. A weight content of the base slurry is 20%; a weight content of the first particles is 21%; and a weight content of the second particles is 59%. Surfaces of the first particles and the second particles are coated with the base slurry, and unit granules are formed.

(10) A plurality of unit granules are pressed into a product. Then, a hot isostatic pressing sintering is performed to the product at a temperature of 1320° C. and a pressure of 80 MPa. After the temperature is maintained for 60 minutes, a first sample D# of a wolfram carbide based hard alloy is prepared. A base slurry on surfaces of first particles and the second particles forms a base C# of the wolfram carbide based hard alloy, and the first particles and the second particles respectively form first hard particles A# and second hard particles B#. FIG. 1 shows a photomicrograph of the first sample D#. In FIG. 1, a light portion in a shape of a net is the base, and a dark portion in a shape of a spot represents hard particles. Weight contents of the first hard particles A#, the second hard particles B# and the base C# are further calculated according to the photomicrograph. Such a calculation method is well-known by those skilled in the art, and it will not be described in detail to avoid redundancy. Mechanical properties of the first sample D# are tested, and test results are shown in Table 1. In Table 1, HRA represents Rockwell hardness, and K.sub.IC represents fracture toughness.

(11) TABLE-US-00001 TABLE 1 Content in a Wear first sample resistance Co, % WC, % HRA D#, % 1/V, cm.sup.−3 K.sub.IC,MN.sup.−3/2 A# 10 90 92.0 21 — — B# 6 94 90.0 59 — — C# 20 80 84.2 20 — — D# 9.64 90.36 88.9 — 9.8 22.6

Embodiment 2

(12) First particles are prepared. WC powder and Co powder are mixed uniformly with a weight ratio of 92:8 and then are sintered at a temperature of 1400° C. After a sintered product is crushed and sieved, the first particles having a size in a range from 10 μm to 20 μm are obtained.

(13) Second particles are prepared. WC powder and Co powder are mixed uniformly with a weight ratio of 94:6 and then are sintered at a temperature of 1400° C. After a sintered product is crushed and sieved, the second particles having a size in a range from 70 μm to 120 μm are obtained.

(14) Base slurry is prepared. WC powder and Co powder are mixed uniformly with a weight ratio of 4:1, and the base slurry is obtained.

(15) The first particles and the second particles are poured into the base slurry. A weight content of the base slurry is 10%; a weight content of the first particles is 24%; and a weight content of the second particles is 66%. Surfaces of the first particles and the second particles are coated with the base slurry, and unit granules are formed.

(16) A plurality of unit granules are pressed into a product. Then, a hot isostatic pressing sintering is performed to the product at a temperature of 1330° C. and a pressure of 85 MPa. After the temperature is maintained for 60 minutes, a second sample H# of the wolfram carbide based hard alloy is prepared. A base slurry on surfaces of first particles and the second particles forms a base G# of the wolfram carbide based hard alloy, and the first particles and the second particles respectively form first hard particles E# and second hard particles F#. FIG. 2 shows a photomicrograph of the second sample H#. In FIG. 2, a light portion in a shape of a net is the base, and a dark portion in a shape of a spot represents hard particles. Weight contents of the first hard particles E#, the second hard particles F# and the base G# are further calculated according to the photomicrograph. Such a calculation method is well-known by those skilled in the art, and it will not be described in detail to avoid redundancy. Mechanical properties of the second sample H# are tested, and test results are shown in Table 2. In Table 2, HRA represents Rockwell hardness, and K.sub.IC represents fracture toughness.

(17) TABLE-US-00002 TABLE 2 Content in a Wear second sample resistance Co, % WC, % HRA D#, % 1/V, cm.sup.−3 K.sub.IC,MN.sup.−3/2 E# 8 92 92.6 24 — — F# 6 94 90.0 66 — — G# 20 80 84.2 10 — — H# 7.88 92.12 89.8 — 11.1 19.3

Embodiment 3

(18) First particles are prepared. WC powder and Co powder are mixed uniformly with a weight ratio of 92:8 and then are sintered at a temperature of 1400° C. After a sintered product is crushed and sieved, the first particles having a size in a range from 10 μm to 20 μm are obtained.

(19) Second particles are prepared. WC powder and Co powder are mixed uniformly with a weight ratio of 94:6 and then are sintered at a temperature of 1400° C. After a sintered product is crushed and sieved, the second particles having a size in a range from 70 μm to 120 μm are obtained.

(20) Base slurry is prepared. WC powder and Co powder are mixed uniformly with a weight ratio of 84:16, and the base slurry is obtained.

(21) The first particles and the second particles are poured into the base slurry. A weight content of the base slurry is 10%; a weight content of the first particles is 24%; and a weight content of the second particles is 66%. Surfaces of the first particles and the second particles are coated with the base slurry, and unit granules are formed.

(22) A plurality of unit granules are pressed into a product. Then, a hot isostatic pressing sintering is performed to the product at a temperature of 1340° C. and a pressure of 95 MPa. After the temperature is maintained for 60 minutes, a third sample L# of the wolfram carbide based hard alloy is prepared. A base slurry on surfaces of first particles and the second particles forms a base K# of the wolfram carbide based hard alloy, and the first particles and the second particles respectively form first hard particles I# and second hard particles J#. FIG. 3 shows a photomicrograph of the third sample L#. In FIG. 3, a dark portion in a shape of a net is the base K#, and a light portion in a shape of a spot represents hard particles. Weight contents of the first hard particles I#, the second hard particles J# and the base K# are further calculated according to the photomicrograph. Such a calculation method is well-known by those skilled in the art, and it will not be described in detail to avoid redundancy. Mechanical properties of the third sample L# are tested, and test results are shown in Table 3. In Table 3, HRA represents Rockwell hardness, and K.sub.IC represents fracture toughness.

(23) TABLE-US-00003 TABLE 3 Content in a Wear third sample resistance Co, % WC, % HRA D#, % 1/V, cm.sup.−3 K.sub.IC,MN.sup.−3/2 I# 8 92 92.6 24 — — J# 6 94 90.0 66 — — K# 16 84 86.1 10 — — L# 7.48 92.52 90.3 — 12.2 15.1

Comparative Embodiment 1

(24) A comparative material M# is prepared. According to a method in the prior art, WC powder and Co powder are mixed with a weight ratio of 90.5:9.5, milled, spray-dried and pressed, and then are sintered at a temperature of 1400° C. so as to prepared a comparative sample M#. Properties of the comparative sample M# are shown in FIG. 4. Mechanical properties of the fourth sample M# are tested, and test results are shown in Table 4. In Table 4, HRA represents Rockwell hardness, and K.sub.IC represents fracture toughness. Besides, test results of samples obtained in Embodiments 1 to 3 are listed in Table 4.

(25) TABLE-US-00004 TABLE 4 Wear resistance Co, % WC, % HRA 1/V, cm.sup.−3 K.sub.IC, MN.sub.−3/2 M# 9.5 90.5 88.6 9.5 14.7 D# 9.64 90.36 88.9 9.8 22.6 H# 7.88 92.12 89.8 11.1 19.3 L# 7.48 92.52 90.3 12.2 15.1

(26) It can be seen from Table 4 that: the hardness, the wear resistance and the fracture toughness of the wolfram carbide based hard alloy according to the present disclosure are all higher than the wolfram carbide based hard alloy prepared according to the method in the prior art. That is, the wolfram carbide based hard alloy according to the present disclosure has very good wear resistance and toughness.

(27) The present disclosure is illustrated in detail in combination with preferred embodiments hereinabove, but it can be understood that the embodiments disclosed herein can be improved or substituted without departing from the protection scope of the present disclosure. In particular, as long as there are no structural conflicts, the technical features disclosed in each and every embodiment of the present disclosure can be combined with one another in any way, and the combined features formed thereby are within the protection scope of the present disclosure. The present disclosure is not limited by the specific embodiments disclosed herein, but includes all technical solutions falling into the protection scope of the claims.