Tool with multi-layer arc PVD coating

Abstract

A tool includes a base body of hard metal, cermet, ceramics, steel or high speed steel and a multi-layer wear protection coating deposited thereon by a PVD process. The wear protection coating has a first coat deposited on the base body having a composition of TiaAl(1-a)N, wherein 0.4a0.6, and a coating thickness of 0.5 m to 4 m, and a second coat deposited on the first coat. The second coat includes a sequence of 10 to 80 first and second layers alternatingly arranged one on top of each other. Each of the first and second layers has a thickness of 5 to 100 nm. Each first layer includes nitrides of the elements Ti, Al, Cr and Si, and each second layer has a composition of TixAl(1-x)N, wherein 0.4x0.6. The first and second coats have up to 10 at-% of further metals, B, C and/or O as impurities in each layer.

Claims

1. A tool comprising: a base body selected from hard metal, cermet, ceramics, steel and high speed steel; and a multi-layer wear protection coating deposited on the base body by a PVD process, wherein the wear protection coating includes a first coat deposited on the base body and having the composition Ti.sub.aAl.sub.(1-a)N, wherein 0.4a0.6 and a coating thickness of 0.5 m to 4 m, a second coat deposited on the first coat and including a sequence of 10 to 80 of each of first layers and second layers alternatingly arranged on top of each other, wherein each of the first and second layers has a layer thickness of from 5 nm to 100 nm, wherein the first layer includes nitrides of elements Ti, Al, Cr and Si, the first layer has a cubic face-centered crystal structure verifiable in an X-ray diffractogram, and wherein the second layer has a composition of Ti.sub.aAl.sub.(1-x)N, wherein 0.4x0.6, and at least one further hard material coat disposed above the second coat, and wherein the first and second coats due to the manufacturing method include up to 10 at -% of metals, B, C and/or O as impurities in each layer.

2. The tool according to claim 1, wherein the PVD process is arc vapor deposition.

3. The tool according to claim 1, wherein the first coat includes a single-layer and/or has a layer thickness within the range of from 1 to 3 m.

4. The tool according to claim 1, wherein the second coat has a sequence of 15 to 70 of each of the first layers and the second layers alternatingly arranged on top of each other, and/or each of the first and second layers of the second coat having a layer thickness of 10 nm to 60 nm, and/or the second coat having a coating thickness of from 0.5 m to 10 m.

5. The tool according to claim 1, wherein the wear protection coating includes a third coat deposited above the second coat and having the composition Ti.sub.bSi.sub.(1-b)N wherein 0.70b0.98 and having a thickness of from 0.05 m to 1 m.

6. The tool according to claim 1, wherein the first layer of the second coat includes 2 to 40 of alternatingly, on top of each other, deposited sub-layers of the compositions Ti.sub.ySi.sub.(1-y)N and Al.sub.zCr.sub.(1-z)N, respectively, wherein 0.70y0.98 and 0.6z0.8 and having a thickness of each of the sub-layers of from 0.5 nm to 15 nm.

7. The tool according to claim 1, wherein cutting edges of the tool are provided with a cutting edge rounding of a radius within the range of from 10 to 100 m.

8. The tool according to claim 1, wherein the wear protection coating has a Vickers hardness HV of from 3000 to 4500, and/or a modulus of elasticity (E-modulus) of >380 GPa,.

9. The tool according to claim 1, wherein the wear protection coating has an average surface roughness Ra, measured along a length of 10 m, of 1.0 m.

10. The tool according to claim 1, wherein the base body made of hard metal includes 5 to 15 at-% Co, 0 to 2 at-% Cr, 0 to 3 at-% carbide, nitride, carbonitride, oxycarbide, oxynitride and/or oxycarbonitride of the elements of the subgroups 4A, 5A and 6A of the periodic system, and balance of WC.

11. The tool according to claim 1, wherein the tool is a solid hard metal drill, an indexable cutting insert, an indexable drilling cutting insert for the machining of iron materials selected from ISO-P materials, ISO-K materials and ISO-M materials.

12. A process for manufacturing of a tool comprising: providing a base body made of hard metal, cermet, ceramics, steel or high-speed steel; depositing a multi-layer wear protection coating on the base body by a PVD process, such as an-arc vapor deposition, wherein on a surface of the base body a first coat is deposited, the first coat having a composition TiAlN, wherein 0.4a0.6 and a coating thickness of from 0.5 m to 4 m, the first coat having a cubic face-centered crystal structure verifiable in an X-ray diffractogram; and depositing on the first coat, a second coat having a sequence of 5 to 100 of each of alternatingly, one on top of each other first layers and second layers, a thickness of each of the first and second layers being of from 5 nm to 100 nm, wherein the deposition of the first layers is effected by the deposition of alternatingly, on top of each other, arranged sub-layers having the compositions Ti.sub.ySi.sub.(1-y)N and Al.sub.zCr.sub.(1-z)N, respectively, wherein 0.70y0.98 and 0.6z0.8 and with a thickness of each of the sub-layers being from 0.5 nm to 15 nm, and wherein the second layer has the composition Ti.sub.xAl.sub.(1-x)N wherein 0.4x0.6.

13. The process of claim 12, further comprising depositing a third coat above the second coat, the third coat having the composition Ti.sub.bSi.sub.(1-b)N, wherein 0.70b0.98 and with a thickness of from 0.05 m to 1 m.

14. The process of claim 12, wherein, after the deposition of the wear protection coating, the tool is subjected to one or more post-treatment steps, wherein at least main cutting edges of the tool are subjected to cutting edge rounding by brushing, and/or a surface of the rake face or of a flute is smoothened by abrasive wet-blasting and/or by abrasive or compacting dry-blasting, and/or by drag finishing, and/or wherein the tool is wet-chemically cleaned.

Description

FIGURES

(1) FIG. 1 shows a schematic representation of an inventive coating on a base body 4 of hard metal, cermet, ceramics, steel or high-speed steel and of a multi-layer wear protection coating deposited on the base body in the PVD process and made of a first coat 1, a second coat 2 consisting of a sequence of first layers 2a and second layers 2b alternatingly arranged on top of each other, and a hard material coat 3 which is herein formed as a covering coat. The circle designated A in the upper representation of FIG. 1 characterizes a detail enlargedly shown in the lower representation of FIG. 1 of essentially the first layer 2a consisting of TiSiN sub-layers and AlCrN sub-layers, respectively, that are alternatingly arranged on top of each other and are herein designated TiSiN-Sub and AlCrN-Sub, respectively.

(2) FIG. 2 shows a X-ray diffractogram of the inventive coating ERF2 described in the examples, the X-ray diffractogram being recorded in Bragg-Brentano geometry (theta-2 theta). The measured reflections exactly correspond to what is expected for a pure cubic crystal structure.

DEFINITIONS AND METHODS

(3) Measurements of Hardness and E-modulus

(4) Hardness and E-modulus (more precisely so-called reduced E-modulus) are measured by nano indentation. In this measurement, a diamond test body according to Vickers is pressed into the layer and the force-path curve is recorded during the measurement. From this curve, it is then possible to calculate the mechanical characteristic values of the test body, inter alia hardness and (reduced) E-modulus. To determine the hardness and E-modulus of the layer according to the invention, a Fischerscope Picodentor HM500 XYp manufactured by Helmut Fischer GmbH, Sindelfingen, Germany was used. It should be noted that the impression depth should not be more than 10% of the layer thickness, otherwise characteristics of the substrate can falsify the measurements. The measurements have been carried out using a test load of 15 mN. In a first step, the test load is applied within 20 seconds in a linearly ascending manner, then the test load is maintained for 10 seconds, and in a third step, the test load is again reduced to zero within 20 seconds, and the test body is lifted off.

(5) Measurement of the Surface Roughness

(6) The surface roughness was measured on polished test surfaces using a measuring device Hommel-ETAMIC TURBO WAVE V7.32 manufactured by HOMMEL ETAMIC GmbH, Schwenningen, Germany (probe: TKU300-96625_TKU300/TS1; measuring range: 80 m; test path: 4.8 mm; speed: 0.5 mm/s).

EXAMPLES

Example 1

Production of Inventive Tools and Comparative Tools

(7) In this example, substrates for solid hard metal (SHM) drills (SUB1), as well as for hard metal indexable cutting inserts (SUB2) were provided with inventive coatings and comparative coatings of the prior art.

(8) Specification of the Solid Hard Metal (SHM) Drill (SUB1)

(9) Diameter: 8.5 mm Nominal drilling depth: 5d Number of cutting edges: 2 Length of cutting edges: 50% of the diameter Spiral angle of the flutes: about 30 Tip angle: 140 Substrate material: hard metal comprising 90 at-% WC, 9.2 at-% Co and 0.8 at-% Cr and having an average WC grain size of 0.7 m
Specification of the Hard Metal Indexable Cutting Inserts (SUB2) Geometry: P6001 Substrate material: hard metal comprising 88 at-% WC, 10.5 at-% Co and 1.5 at-% mixed carbides (TiC, TaC and NbC) and having an average WC grain size of about 5 m
Specification of the Holder for the Hard Metal Indexable Cutting Inserts (SUB2) Diameter: 18 mm Nominal drilling depth: 5d Number of cutting edges: 2 Length of cutting edges: 50% of the diameter Spiral angle of the flutes: about 20 Tip angle: 140
Pre- and Post-treatments of the Substrate

(10) Prior to the coating of the substrates, the main cutting edges were subjected to cutting edge rounding to a radius of 20-60 m by brushing, the flutes were smoothened by wet-blasting using corundum, and the substrate was wet-chemically cleaned. After the coating of the substrates, the flutes were smoothened by wet-blasting using corundum. The pre- and post-treatments were carried out in the same way with the tools coated according to the invention, as well as with the comparative tools.

(11) Manufacturing of an Inventive Coating (ERF1 and ERF2)

(12) The entire coating was deposited by arc vapor deposition in a single run without interruption of the deposition process.

(13) First Coat: First, a 1.7 m thick, single-layer first TiAlN coat (1) was deposited on the substrate surface from two TiAl mixed targets (Ti:Al=50:50) (Bias: 50 V DC; 4 Pa nitrogen; 160 A evaporator current each; deposition temperature: 550 C.).

(14) Second Coat: Above the first coat a multi-layer second coat (2) was deposited, consisting of a sequence of 40 of each of first layers (2a) of TiAlCrSiN and second layers (2b) of TiAlN alternatingly arranged on top of each other.

(15) Each of the first TiAlCrSiN layers (2a) consisted of 4 TiSiN sub-layers and 4 AlCrN sub-layers alternatingly deposited on top of each other. The TiSiN sub-layers were deposited from two TiSi mixed targets (Ti:Si=85:15), and the AlCrN sub-layers were deposited from two AlCr mixed targets (Al:Cr=70:30) (Bias: 60 V DC; 4 Pa nitrogen; 160 A evaporator current each; deposition temperature 550 C.). The thickness of the individual sub-layers was about 5 nm so that each of the first TiAlCrSiN layers (2a) had a thickness of about 40 nm.

(16) The second TiAlN layers (2b) were deposited from two Ti-Al mixed targets (Ti:Al=50:50) (Bias: 60 V DC; 4 Pa nitrogen; 160 A evaporator current each; deposition temperature 550 C.). The thickness of each of the second TiAlN layers (2b) was about 40 nm.

(17) Third Coat: For a first inventive coating (ERF1) a single-layer third TiSiN coat (3) was deposited above the second coat as a decorative coat having a thickness of 0.2 m from two Ti-Si mixed targets (Ti:Si=85:15) (Bias: 30 V DC; 3.5 Pa nitrogen; 180 A evaporator current each; deposition temperature 480 C.). For the deposition of this coat the deposition temperature was selected slightly lower than for the previous coats to accelerate the cooling process and to shorten the total process time a little bit.

(18) A second inventive coating (ERF2) comprised only the first coat (1) and the second coat (2), but not the third coat (3). For measurements on the second coat (2), for example, hardness measurements or X-ray structure analysis, coated tools having the second inventive coating (ERF2) were used, having only the first coat (1) and the second coat (2) deposited thereon, but not the third coat (3). For machining tests there is individually indicated which one of the inventive coatings was used (ERF1 or ERF2).

(19) The deposition temperature in the PVD process has a significant influence on the cleanliness of the substrate prior to the coating. The higher the temperature is, the more impurities on the tool from previous operation steps are removed or simply evaporated, respectively. For substrates made of HSS steel the deposition temperatures are often a compromise between good cleaning and avoidance of thermal damages to the substrate. For hard metal substrates it is not required to enter into such compromises.

(20) Manufacturing of Comparative Coatings (VGL1, VGL2 and VGL3)

(21) Comparative Coating 1 (VGL1):

(22) On the substrate surface there was first deposited a primer layer system for the improvement of the adhesion, the system consisting of a TiN layer and a TiAlN layer. The TiN layer was deposited from two Ti targets (Bias: 200 V DC; 0.8 Pa nitrogen; 180 A evaporator current each; deposition temperature: 450 C.). The thickness of the TiN layer was about 100 nm. The TiAlN layer was deposited from two Ti-Al mixed targets (Ti:Al=50:50) and two Ti targets (Bias: 40 V DC; 3.2 Pa nitrogen; 200 A evaporator current (Ti targets), 210 A evaporator current (TiAl targets); deposition temperature: 450 C.). The thickness of the TiAlN layer was about 40 nm.

(23) Subsequently, a multi-layer coat of a sequence of 11 of each of layers consisting of TiAlN and TiN was deposited alternatingly on top of each other. The TiAlN layers were deposited from two Ti-Al mixed targets (Ti:Al=50:50) and two Ti targets, and the TiN layers were deposited from two Ti targets (Bias: 40 V DC; 3.2 Pa nitrogen; 200 A evaporator current (Ti targets), 210 A evaporator current (TiAl targets); deposition temperature: 450 C.). The thickness of each of the TiAlN layers was about 200 nm, and the thickness of each of the TiN layers was about 100 nm, so that the coating had a total thickness of about 3,300 nm.

(24) A coat of TiAlN having a higher Al content was deposited as a covering layer from two Ti targets (Bias: 40 V DC; 3.2 Pa nitrogen; 210 A evaporator current; deposition temperature: 450 C.). The thickness of the TiAlN layer was about 500 nm.

(25) Comparative Coating 2 (VGL2):

(26) On the substrate surface there was first deposited a primer layer to improve the adhesion. The parameters for this primer layer were: 4 AlCr mixed targets (Al:Cr=70:30); evaporator current: 160 A each; pressure: 3.5 Pa nitrogen; 50 V DC Bias; temperature: 480 C.; layer thickness: about 100 nm.

(27) Subsequently, a multi-layer coat of a sequence of 10 of each alternatingly on top each other deposited layers of TiSiN and AlCrN were deposited. Each of these layers consisted of 4 sub-layers. The first sub-layer was produced from two TiSi mixed targets (Ti:Si=85:15) with a an evaporator current of 180 A, and from 4 AlCr mixed targets (Al:Cr=70:30) with an evaporator current of 150 A. The remaining parameters were: pressure: 3.5 Pa nitrogen; 30 V DC Bias; temperature: 480 C.; sub-layer thickness: about 50 nm. The second sub-layer was produced from two TiSi mixed targets (Ti:Si=85:15) with an evaporator current of 180 A. The remaining parameters were: pressure: 3.5 Pa nitrogen; Bias: 30 V DC; temperature: 480 C.; sub-layer thickness: about 50 nm. The third sub-layer had the same structure and the same coating thickness as the first layer. The fourth sub-layer was produced using 4 AlCr mixed targets (Al:Cr=70:30). The parameters were: evaporator current: 160 A; pressure: 3.5 Pa nitrogen; Bias: 40 V DC; temperature: 480 C.; sub-layer thickness: about 200 nm.

(28) In addition, a covering layer was deposited on the multi-layer system. The parameters for this covering layer were: 2 TiSi mixed targets (Ti:Si=85:15); evaporator current: 180 A each; pressure: 3.5 Pa nitrogen; Bias: 30 V DC; temperature: 480 C.; layer thickness: about 300 nm.

(29) Comparative Coating 3 (VGL3):

(30) The comparative coating 3 (VGL3) was a combination of the comparative coatings 1 and 2. First, a comparative coating 1 (VGL1) was deposited on the substrate surface according to the above-described method. Subsequently, the coated substrate body was cooled down, removed from the coating reactor, smoothened in the flute by wet-blasting, and finally reintroduced into the coating reactor to deposit a comparative coating 2 (VGL2) according to the above-described method.

(31) Mechanical Properties of the Coatings

(32) Hardness and E-modulus of the inventive coating ERF2 (without the third coat (3)), as well as of the comparative coatings VGL1 and VGL2 were measured, as described above, and are indicated in the following table 1.

(33) Furthermore, the maximum operating temperature of the coated tools was estimated on the basis of literature indications. In many cases of operation, known TiAlN coatings have an operating temperature of a maximum of 900 C.

(34) TABLE-US-00001 TABLE 1 Max. operating Hardness E-modulus temperature Coating [HV] [GPa] [ C.] ERF2 3600 HV 460 GPa about 1000 C. VGL1 3000 HV 430 GPa about 700 C. VGL2 3600 HV 440 GPa about 1000 C.

Example 2

Machining Tests

(35) Tools produced according to example 1 were compared in machining tests (drilling).

(36) Machining Test 1

(37) Using solid hard metal drills (SUB1) having the coatings ERF2, VGL1, VGL2 and VGL3, respectively, blind holes of a depth of 18 mm were produced in an alloyed steel material, 42 CrMo4 (1.7225 according to EN10027-2) having a strength of 850 N/mm.sup.2 (v.sub.c=120 m/min; f=0.23 mm/U; internal cooling with KSS 5% and 20 bars).

(38) The machining was terminated at an average flank wear of V.sub.b>0.2 mm or a maximum flank wear V.sub.bmax>0.25 mm, and the tool life distance reached until then was determined. The results are indicated in the following table 2 as the average tool life distance of three tests.

(39) TABLE-US-00002 TABLE 2 Average tool life distance Substrate/Coating [m] SUB1/ERF2 32 SUB1/VGL1 10 SUB1/VGL2 15 SUB1/VGL3 22

(40) Tools having the inventive coating reached significantly higher average tool life distances than the tools with the comparative coatings.

(41) Machining Test 2

(42) Using solid hard metal drills (SUB1) having the coatings ERF2 and VGL3, respectively, blind holes of a depth of 40 mm were produced in an unalloyed steel material (C45E according to EN10020, corresponding to Ck 45 according to DIN 17200) having a strength of 600 N/mm.sup.2 (v.sub.c=175 m/min; f=0.3 mm/U; internal cooling with KSS 5% and 20 bars).

(43) The machining was terminated at an average flank wear of V.sub.b>0.2 mm or a maximum flank wear V.sub.bmax>0.25 mm, and the tool life distance reached until then was determined. The results are indicated in the following table 3 as the average tool life distance of three tests.

(44) TABLE-US-00003 TABLE 3 Average tool life distance Substrate/Coating [m] SUB1/ERF2 104 SUB1/VGL3 89

(45) Tools having the inventive coating reached significantly higher average tool life distances than the tools with the comparative coatings. The variation among the results of the tools coated according to the invention was also lower than for the comparative tools.

(46) Machining Test 3

(47) Using indexable cutting inserts (SUB2) having the coatings ERF2 and VGL3 as well as the above-described holder, blind holes of a depth of 52 mm were produced in an cast iron material (EN-GJL-250 to EN1561, corresponding to GG25 according to DIN 1691) (v.sub.c=160 m/min; f=0.28 mm/U; internal cooling with KSS 5% and 20 bars).

(48) The machining was terminated at an average flank wear of V.sub.b>0.3 mm or a maximum flank wear V.sub.bmax>0.4 mm, and the tool life distance reached until then was determined. The results are indicated in the following table 4 as the average tool life distance of three tests.

(49) TABLE-US-00004 TABLE 4 Average tool life distance Substrate/Coating [m] SUB2/ERF2 68 SUB2/VGL3 64

(50) Tools having the inventive coating reached significantly higher average tool life distances than the tools with the comparative coatings.

(51) Machining Test 4

(52) Using solid hard metal drills (SUB1) having the coatings ERF, ERF2 and VGL3, respectively, blind holes of a depth of 20 mm were produced in an unalloyed steel material (C45E according to EN10020, corresponding to Ck 45 according to DIN 17200) having a strength of 600 N/mm.sup.2 (v.sub.c=170 m/min; f=0.3 mm/U; internal cooling with KSS 5% and 20 bars).

(53) The machining was terminated at an average flank wear of V.sub.b>0.25 mm or a maximum flank wear V.sub.bmax>0.3 mm, and the tool life distance reached until then was determined. The results are indicated in the following table 5.

(54) TABLE-US-00005 TABLE 5 Average tool life distance Substrate/Coating [m] SUB1/ERF2 80 SUB1/ERF1 87 SUB1/VGL1 29

(55) Tools having the inventive coating reached significantly higher average tool life distances than the tools with the comparative coatings. The variation among the results of the tools coated according to the invention was also lower than for the comparative tools, especially for the tools with inventive coating ERF1.