CA2060723C - Heat-resistant sintered hard alloy - Google Patents
Heat-resistant sintered hard alloyInfo
- Publication number
- CA2060723C CA2060723C CA 2060723 CA2060723A CA2060723C CA 2060723 C CA2060723 C CA 2060723C CA 2060723 CA2060723 CA 2060723 CA 2060723 A CA2060723 A CA 2060723A CA 2060723 C CA2060723 C CA 2060723C
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- 229910045601 alloy Inorganic materials 0.000 title claims abstract description 77
- 239000000956 alloy Substances 0.000 title claims abstract description 77
- 239000010941 cobalt Substances 0.000 claims abstract description 57
- 229910017052 cobalt Inorganic materials 0.000 claims abstract description 57
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims abstract description 57
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 34
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims abstract description 32
- 239000011651 chromium Substances 0.000 claims abstract description 24
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims abstract description 20
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 20
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 claims abstract description 19
- 239000010949 copper Substances 0.000 claims abstract description 19
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims abstract description 18
- 229910052721 tungsten Inorganic materials 0.000 claims abstract description 18
- 239000010937 tungsten Substances 0.000 claims abstract description 18
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims abstract description 17
- 229910052802 copper Inorganic materials 0.000 claims abstract description 17
- 229910052742 iron Inorganic materials 0.000 claims abstract description 16
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 16
- 229910052796 boron Inorganic materials 0.000 claims abstract description 15
- 239000012535 impurity Substances 0.000 claims abstract description 10
- 239000011159 matrix material Substances 0.000 claims description 17
- 239000012071 phase Substances 0.000 description 23
- 239000000843 powder Substances 0.000 description 17
- 230000003647 oxidation Effects 0.000 description 13
- 238000007254 oxidation reaction Methods 0.000 description 13
- 239000000463 material Substances 0.000 description 11
- 238000005260 corrosion Methods 0.000 description 8
- 230000007797 corrosion Effects 0.000 description 8
- 229910052751 metal Inorganic materials 0.000 description 7
- 230000007423 decrease Effects 0.000 description 6
- 239000002184 metal Substances 0.000 description 6
- 239000000203 mixture Substances 0.000 description 6
- 238000006467 substitution reaction Methods 0.000 description 6
- 238000005245 sintering Methods 0.000 description 5
- 239000007787 solid Substances 0.000 description 5
- 150000001875 compounds Chemical class 0.000 description 4
- 238000000034 method Methods 0.000 description 4
- 238000002156 mixing Methods 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 3
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- -1 W6Co7 are formed Chemical compound 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 239000007791 liquid phase Substances 0.000 description 2
- 150000001247 metal acetylides Chemical class 0.000 description 2
- 150000004767 nitrides Chemical class 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- OFEAOSSMQHGXMM-UHFFFAOYSA-N 12007-10-2 Chemical compound [W].[W]=[B] OFEAOSSMQHGXMM-UHFFFAOYSA-N 0.000 description 1
- QYEXBYZXHDUPRC-UHFFFAOYSA-N B#[Ti]#B Chemical compound B#[Ti]#B QYEXBYZXHDUPRC-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229910000684 Cobalt-chrome Inorganic materials 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 241000669326 Selenaspidus articulatus Species 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 229910033181 TiB2 Inorganic materials 0.000 description 1
- 229910009043 WC-Co Inorganic materials 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- WRSVIZQEENMKOC-UHFFFAOYSA-N [B].[Co].[Co].[Co] Chemical compound [B].[Co].[Co].[Co] WRSVIZQEENMKOC-UHFFFAOYSA-N 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 239000010952 cobalt-chrome Substances 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000001192 hot extrusion Methods 0.000 description 1
- 238000001513 hot isostatic pressing Methods 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 229910000765 intermetallic Inorganic materials 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 230000005298 paramagnetic effect Effects 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000009707 resistance sintering Methods 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 230000004584 weight gain Effects 0.000 description 1
- 235000019786 weight gain Nutrition 0.000 description 1
- 238000001238 wet grinding Methods 0.000 description 1
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- Powder Metallurgy (AREA)
- Ceramic Products (AREA)
Abstract
A heat-resistant sintered hard alloy comprises 35% to 95% by weight of a WCoB type complex boride in a cobalt base alloy. The alloy contains 1.5% to 4.1% boron, 19.1% to 69.7% tungsten, optionally 1 to 25% chromium, the balance being cobalt and a maximum of 1% impurities. Nickel, iron and/or copper may be substituted for portions of the cobalt content.
Description
~~~ 3 Backq~ound of the Invention The present invention relates to a heat-resistant sintered hard alloy, composed of a hard phase consisting mainly of a WCoB
type complex boride, and a cobalt base alloy matrix phase binding the hard phase which hard alloy exhibits excellent room temperature characteristics as well as excellent high temperature characteristics such as high temperature strength and oxidation resistance, and as a hot extruding die for a copper rod.
Requirements for wear-resistant sintered hard materials have become increasingly severe, and the industry has sought improved materials having wear-resistance as well as heat-resistance and corrosion resistance or the like.
As sintered hard materials, carbides, nitrides and carbonitrides such as WC base hard alloys and TiCN type cermets are well known. ~s substitute materials for t~le aforementioned hard materials, hard alloys and cermets including metallic borides such as WB and TiBz, and metallic complex borides such as MozFeBz and Mo2NiB2 have been recently proposed, noting excellent properties of borides such as extreme hardness, high melting point and high electric conductivity. Further, stellites are utilized as cobalt base wear-resistant materials.
A hard alloy formed by binding WB with a nickel base alloy such a--. disclosed i.n Japanese Patent Pu~licat.ions No. Sho 56-45985, No. Sho 56-45986 and No. Sho 56-45987 is a paramagnetic wear-resistant material to be used especially in watch cases and ornaments, and is not intended for structural materials to be used at high temperature.
Ceramics comprising metallic borides such as TiB2 as disclosed in Japanese Patent Publications No. Sho 61-50909 and No. Sho 63-5353 exhibit extreme hardness and pronounced heat resistance, but impart poor thermal shock resistance due to there being no metallic binding matrix phase.
Generally, hard materials formed by adding metals to metallic borides suffer from the disadvantage in that they tend to form a brittle third phase, and it is difficult to obtain high strength or toughness.
Hard alloys comprising metallic complex borides such as Mo2FeB2 and Mo2NiB2 formed by reaction during sintering have been developed to eliminate the above disadvantage.
A Mo2FeB2 type hard alloy disclosed in Japanese Patent Publication No. Sho 60-57499 has excellent mechanical properties, wear-resistance and corrosion resistance at room temperature but unsatisfactory high temperature strength and oxidation resistance due to its iron base binding matrix phase.
A Mo2NiB2 type hard alloy disclosed in Laid Open Japanese Patent application No. Sho 62-196353 has excellent high temperature properties and corrosion resistance, but poor wear-resistance and anti-adhesion property, since the complex boride Mo2NiB2 is about 15 GPa at micro-Vickers hardness and is not so hard, and its binding phase consists of nickel base alloy. Stellites exhibit excellent high temperature properties, but their hardness is too low to be used for wear-resistant materials.
It is an object of the present invention to provide a sintered hard alloy having excellent room temperature properties as well as pronounced high temperature properties such as high temperature strength and oxidation resistance.
Summary of the Invention According to the present invention, there is provided a heat-resistant sintered hard alloy comprising 35 to 95% by weight of a WCoB type complex boride and a cobalt base alloy matrix phase. The hard alloy may consist of boron of 1.5 to 4.1% by weight, tungsten of 19.1 to 69.7% by weight with the balance being cobalt and unavoidable impurities. In addition to the above elements, the hard alloy may contain chromium of 1 to 25% by weight for the improvement of mechanical properties and corrosion resistance. Further, the hard alloy may comprise boron of 1.5 to 4.1% by weight, tungsten of 19.1 to 69.7% by weight, chromium of 1 to 25% by weight, and at least one of nickel, iron and copper. Nickel, when present, substitutes for cobalt in the ramge of 0.2 to 30% by weight of cobalt content.
Iron when present, substitutes for cobalt in the range of 0.2 to 15% by weight of cobalt content. Copper, when present, substitutes for cobalt in the range of 0.1 to 7.5% by weight of cobalt content. The balance of this alloy consists of cobalt and unavoidable impurities.
Detailed Description of the Invention In this description, WCoB and a complex boride identified as WCoB by means of x-ray diffraction comprising tungsten and cobalt, in which part of tungsten may be replaced by chromium and part of the cobalt may be replaced by chromium, nickel, iron or copper, will be referred to as a WCoB type complex boride.
The WCoB type complex boride offers the following advantages. The formation of a brittle third phase, which tends to be formed in a boride base hard alloy, can be suppressed by forming the WCoB type complex boride by reaction during sintering. The micro-Vickers hardness of the WCoB type boride is larger than 30 GPa, and higher than those of other metallic complex borides such as Mo2FeB2 and Mo2NiB2, and the same as or higher than those of carbides and nitrides which are currently used for hard materials. Further, the WCoB type complex boride has excellent oxidation resistance.
In the case where the content of the WCoB type complex boride is less than 35% by weight, the wear resistance of the hard alloy is reduced due to the insufficient amount of the complex boride, and is liable to marked deformation at hi~h temperature due to insufficient development of complex boride networks in the cobalt base alloy matrix phase. On the other hand, in the case where the content of the WCoB type complex boride is more than 95% by weight, the strength of the hard alloy is remarkably decreased, though its hardness is increased. For the above reason, it is preferable that the content of the WCoB type complex boride be 35 to 95% by weight.
Boron is an essential element for forming the WCoB type complex boride in the heat-resistant sintered hard alloy. With boron less than 1.5% by weight, the complex boride is less than 35%
by weight, and with boron more than 4.1% by weight, the complex bor~de is over 95% by weight, leading to a pronounced decrease in the strength of the hard alloy. For the above reason, it is preferable that the amount of boron in the hard alloy be from 1.5 to 4.1% by weight.
Tungsten is also an essential element for forming the WCoB
type complex boride. The stoichiometric ratio in the WCoB type complex boride is such that W:Co:B = 1:1:1. The WCoB type complex boride which is practically applicable, however, need not be a perfectly stoichiometric compound, but may have a composition variance of a few percent. Accordingly, the molecular ratio of W/B
(hereafter will be referred to as W/B ratio) need not be 1, but it i~ importilnt tha~ the W/B ratio be within a specific range including 1 as the approximate centre.
type complex boride, and a cobalt base alloy matrix phase binding the hard phase which hard alloy exhibits excellent room temperature characteristics as well as excellent high temperature characteristics such as high temperature strength and oxidation resistance, and as a hot extruding die for a copper rod.
Requirements for wear-resistant sintered hard materials have become increasingly severe, and the industry has sought improved materials having wear-resistance as well as heat-resistance and corrosion resistance or the like.
As sintered hard materials, carbides, nitrides and carbonitrides such as WC base hard alloys and TiCN type cermets are well known. ~s substitute materials for t~le aforementioned hard materials, hard alloys and cermets including metallic borides such as WB and TiBz, and metallic complex borides such as MozFeBz and Mo2NiB2 have been recently proposed, noting excellent properties of borides such as extreme hardness, high melting point and high electric conductivity. Further, stellites are utilized as cobalt base wear-resistant materials.
A hard alloy formed by binding WB with a nickel base alloy such a--. disclosed i.n Japanese Patent Pu~licat.ions No. Sho 56-45985, No. Sho 56-45986 and No. Sho 56-45987 is a paramagnetic wear-resistant material to be used especially in watch cases and ornaments, and is not intended for structural materials to be used at high temperature.
Ceramics comprising metallic borides such as TiB2 as disclosed in Japanese Patent Publications No. Sho 61-50909 and No. Sho 63-5353 exhibit extreme hardness and pronounced heat resistance, but impart poor thermal shock resistance due to there being no metallic binding matrix phase.
Generally, hard materials formed by adding metals to metallic borides suffer from the disadvantage in that they tend to form a brittle third phase, and it is difficult to obtain high strength or toughness.
Hard alloys comprising metallic complex borides such as Mo2FeB2 and Mo2NiB2 formed by reaction during sintering have been developed to eliminate the above disadvantage.
A Mo2FeB2 type hard alloy disclosed in Japanese Patent Publication No. Sho 60-57499 has excellent mechanical properties, wear-resistance and corrosion resistance at room temperature but unsatisfactory high temperature strength and oxidation resistance due to its iron base binding matrix phase.
A Mo2NiB2 type hard alloy disclosed in Laid Open Japanese Patent application No. Sho 62-196353 has excellent high temperature properties and corrosion resistance, but poor wear-resistance and anti-adhesion property, since the complex boride Mo2NiB2 is about 15 GPa at micro-Vickers hardness and is not so hard, and its binding phase consists of nickel base alloy. Stellites exhibit excellent high temperature properties, but their hardness is too low to be used for wear-resistant materials.
It is an object of the present invention to provide a sintered hard alloy having excellent room temperature properties as well as pronounced high temperature properties such as high temperature strength and oxidation resistance.
Summary of the Invention According to the present invention, there is provided a heat-resistant sintered hard alloy comprising 35 to 95% by weight of a WCoB type complex boride and a cobalt base alloy matrix phase. The hard alloy may consist of boron of 1.5 to 4.1% by weight, tungsten of 19.1 to 69.7% by weight with the balance being cobalt and unavoidable impurities. In addition to the above elements, the hard alloy may contain chromium of 1 to 25% by weight for the improvement of mechanical properties and corrosion resistance. Further, the hard alloy may comprise boron of 1.5 to 4.1% by weight, tungsten of 19.1 to 69.7% by weight, chromium of 1 to 25% by weight, and at least one of nickel, iron and copper. Nickel, when present, substitutes for cobalt in the ramge of 0.2 to 30% by weight of cobalt content.
Iron when present, substitutes for cobalt in the range of 0.2 to 15% by weight of cobalt content. Copper, when present, substitutes for cobalt in the range of 0.1 to 7.5% by weight of cobalt content. The balance of this alloy consists of cobalt and unavoidable impurities.
Detailed Description of the Invention In this description, WCoB and a complex boride identified as WCoB by means of x-ray diffraction comprising tungsten and cobalt, in which part of tungsten may be replaced by chromium and part of the cobalt may be replaced by chromium, nickel, iron or copper, will be referred to as a WCoB type complex boride.
The WCoB type complex boride offers the following advantages. The formation of a brittle third phase, which tends to be formed in a boride base hard alloy, can be suppressed by forming the WCoB type complex boride by reaction during sintering. The micro-Vickers hardness of the WCoB type boride is larger than 30 GPa, and higher than those of other metallic complex borides such as Mo2FeB2 and Mo2NiB2, and the same as or higher than those of carbides and nitrides which are currently used for hard materials. Further, the WCoB type complex boride has excellent oxidation resistance.
In the case where the content of the WCoB type complex boride is less than 35% by weight, the wear resistance of the hard alloy is reduced due to the insufficient amount of the complex boride, and is liable to marked deformation at hi~h temperature due to insufficient development of complex boride networks in the cobalt base alloy matrix phase. On the other hand, in the case where the content of the WCoB type complex boride is more than 95% by weight, the strength of the hard alloy is remarkably decreased, though its hardness is increased. For the above reason, it is preferable that the content of the WCoB type complex boride be 35 to 95% by weight.
Boron is an essential element for forming the WCoB type complex boride in the heat-resistant sintered hard alloy. With boron less than 1.5% by weight, the complex boride is less than 35%
by weight, and with boron more than 4.1% by weight, the complex bor~de is over 95% by weight, leading to a pronounced decrease in the strength of the hard alloy. For the above reason, it is preferable that the amount of boron in the hard alloy be from 1.5 to 4.1% by weight.
Tungsten is also an essential element for forming the WCoB
type complex boride. The stoichiometric ratio in the WCoB type complex boride is such that W:Co:B = 1:1:1. The WCoB type complex boride which is practically applicable, however, need not be a perfectly stoichiometric compound, but may have a composition variance of a few percent. Accordingly, the molecular ratio of W/B
(hereafter will be referred to as W/B ratio) need not be 1, but it i~ importilnt tha~ the W/B ratio be within a specific range including 1 as the approximate centre.
2¢~ 3 Test results indicate that in the case where the W/B ratio is far smaller than l, cobalt borides such as Co2B is ormed, and in the case where the W/B ratio is far larger than 1, intermetallic compounds of tungsten and cobalt such as W6Co7 are formed, leading to a decrease in the strength of the hard alloy in both cases.
When the W/B ratio is within the range of 0.75 to 0.135 x (11.5-X), where X indicates the content of boron by weight percent, even if the above third phase is formed, the third phase will little affect the strength of the hard alloy; i.e., there would be an allowable decrease in the strength.
In the case where the W/B ratio is larger than 1, part of excess tungsten will be solid solute into the cobalt base alloy matrix phase, which will strengthen the matrix phase, thus improving the mechanical properties of the heat-resistant sintered hard alloy. ~owever, since the amount of the cobalt base alloy matrix phase decreases with the increase of the amount of the WCoB
type complex boride, it is necessary to decrease the amount of said excess tungsten in the matrix phase accompanied by the above increase, so as to maintain the strength of the hard alloy.
For the above reason, it is preferable that the upper limit of the amount of tungsten be 1.35 in terms of the W/B ratio in the case where the amount of boron is lowest (1.5% by weight), and 1 in terms of the W/B ratio in the case where the amount of boron is highest (~.1% by weight). This range is represented by the formula ,, , 2~
0.135 x (11.5-X), in which X is the weight percent of boron.
Accordingly, it is desirable that the amount of tungsten in the hard alloy be in the range of from 0.75 to 0.1~5 x (11.5-X), preferably in the range of 0.~ to 0.135 x (11.5-X) in terms of the W/B ratio; that is, from 19.1 to 69.7% by weight, preferably from 20.4 to 69.7% by weight, in said hard alloy.
In the case of a sintered hard alloy containing chromium, it is presumed that chromium will be solid solute into the WCoB type complex boride, and form a (wxcoycrz)s multiple boride of the WCoB
type complex boride, in which cobalt rather than tungsten is replaced partially by chromium and x + y + z is equal to 2, and further chromium will be solid solute into the cobalt base alloy matrix also, so that the resistances to corrosion, heat and oxidation of the sintered hard alloy will be improved.
Furthermore, chromium refines the (WxCoyCrz)8 multiple boride pha6e and improves the mechanical properties of the sintered hard alloy. With a content of chromium below 1% by weight, the above-mentioned improvement can not be attained, and with the content of chromium above 25% by weight, the mechanical properties of the 6intered hard alloy are remarkably decreased due to the generation of a brittle phase such as a CoCr sigma (a) phase. Accordingly, it is preferable that the content of chromium be from 1 to 25% by weight.
2~2~3 ,........................................................................ .
.
In the case of a sintered hard alloy containing nickel, it is presumed that nickel will substitute for cobalt and be solid solute into the co~alt base alloy matrix phase, and improve the mechanical properties, corrosion resistance and heat-resistance of the hard alloy. With the substitution of nickel below 0.2% by weight of cobalt content, the aforementioned improvements of mechanical ~' properties and the like can not be attained, and with the substitution of nickel above 30% by weight of cobalt, abrasion resistance is reduced due to the decrease of hardness.
Accordingly, it i5 preferable that nickel substitute for cobalt in the range of 0.2 to 30 % by weight of cobalt content.
Iron substitutes mainly for cobalt in the WCoB type complex boride and the cobalt base alloy matrix phase, and improves the strength at low temperature. With the substitution of iron below 0.2% by weight of cobalt content, the aforementioned improvement is not attained, and with the substitution of iron more than 15%
by weight of cobalt content, the hard alloy becomes less resistant to corrosion, heat and oxidation. Accordingly, in the case of the sintered hard alloy containing iron, it is preferable that iron substitute for cobalt in the range of 0.2 to 15% by weight of cobalt content.
Copper substitutes for cobalt and is solid solute into the cobalt base alloy matrix phase, and improves the corrosion ~esistance and heat c~nductivity of the sintered hard alloy. With the substitution of copper below 0.1% by weight of cobalt content, :, _ g _ Z~7.~3 the above improvements are not attained, and with the substitution of copper more than 7.5% by weight o~ cobalt content, the mechanical properties and heat-resistance are degraded.
Accordingly, it is preferable that copper substitute for cobalt in the range of 0.1 to 7.5% by weight of cobalt content, when copper is added to the sintered hard alloy.
The unavoidable impurities contained in the sintered hard alloy are mainly silicon, aluminum, manganese, magnesium, phosphorus, sulfur, nitrogen, oxygen, carbon or the like, and it is desirable that the content of these impurity elements be as little as possible. However, in the case where the total amount of these impurity elements is less than 1.0% by weight, the detrimental effects thereof to the properties of the sintered hard alloy are relatively small. Accordingly, it is preferable that the total content of the unavoidable impurities be less than 1.0% by weight, more preferably less than 0.5% by weight.
In the case where the sintered hard alloy is employed for a wear-resistant coating in which the strength is not of critical importance, and silicon and aluminum or the like are added intentionally so as to improve the oxidation resistance of the coating, the total content of the aforementioned elements may be over 1.0% by weight.
The sintered hard alloy is made by mixing boride powders of tungstel~, cobalt, chromium, nickel and iron; alloy powders of boron, with at least one of tungsten, cobalt, chromium, nickel, iron and copper; or boron powder and metal powders of tungsten, cobalt, chromium, nicXel, iron and copper, or alloy powders containing at least two of these metallic elements, thereafter wet milling the mixture with an organic solvent by means of a vibrating ball mill or the like, drying, granulating, and forming, followed by liquid phase sintering of the green compact in a non-oxidizing atmosphere such as in vacuum, a reducing gas, or an inert gas.
The hard phase, that is the WCoB type complex boride of the sintered hard alloy, is formed by the reaction during sintering.
A powder mixture obtained by blending metal powders such as cobalt, chromium and nickel to form the Co base alloy matrix phase, with the WCoB type complex boride such as WCoB and (WxCoyCrz)B which are prepared by reacting tungsten boride, cobalt boride, boron powder with metal powders such as tungsten, cobalt and chromium etc. in a furnace in advance, may be employed as the raw material powders also.
The liquid phase sintering is usually carried out at the temperature range of 1100 to 1400~C and for 5 to 90 minutes depending on the composition of the hard alloy. A hot press method, a hot isostatic pressing method, and an electric resistance sintering method or the like ma~ be also employed.
EXAMPLES
The compound powders listed in Table 1 and metal powders listed in Table 2 were blended in the compositions shown in Table 3 with the blending ratios shown in Table 5. The blended powders were wet milled with acetone by means of a vibrating ball mill for 28 hours and then dried and granulated. The powders thus obtained were pressed into a predetermined shape. The green compacts were sintered at the temperature of 1150 to 1300~C for 30 minutes in vacuum.
The transverse rupture strength and Rockwell A.
scale hardness (RA) at room temperature, the transverse rupture strength at 900~C, and the weight gain by oxidation after holding at the temperature of 900~C for 1 hour in still air of the samples of the hard alloys thus obtained are shown in Table 7.
Sample Nos. 1 to 10 all show extreme hardness ~and high transverse rupture strength at room temperature as well as high transverse rupture strength and excellent oxidation resistance at the high temperature. A hot extruding die was prepared using the hard alloy of sample No. 6, and a pure copper rod was extruded through the die. It was possible to extrude the rod 50 to 100 times satisfactorily. A similar die formed with a WC-Co type hard alloy could not be used practically for the pure copper rod hot extrusion.
COMPARATIVE EXAMPLES
The compound powders listed in Table 1 and the metal powders listed Table 2 were blended in the composition shown in Table 4 with the blending ratios shown in Table 6.
The hard alloys were prepared by the same method as shown in the EXAMPLES, and the properties thereof are shown in Table 8.
Sample No. 11 has a W/B ratio less than 0.75, and exhibits low transverse rupture strength at room temperature as well as the high temperature. Sample No. 12 exhibits low transverse rupture strength at the high temperature and poor oxidation resistance due to the content of iron being higher than 10% by weight, though it shows high transverse rupture strength at room temperature. Sample No. 13, containing a MoCoB type complex boride instead of the WCoB
type complex boride, exhibits low transverse rupture strength at room temperature as well as the high temperature, compared with the 6amples of EXAMPLES ha~ing approximately the same hardness. Sample No. 14 containing a Mo2FeB2 type complex boride exhibits low transverse rupture strength at high temperature and po~r oxidation resistance.
A similar hot extruding die as described in the EXAMPLES was prepared using the hard alloy of Sample No. 14, and a copper rod was extruded in the same manner as in the case of the EXAMPLES.
~nly 5 to 10 times extruding was possible with the die.
T~ble 1 Compound ~3 C N ~ W Fe . Cr Mo powder wt% wt% wt% wt96 wt% wt% w t% wt~
WB 5.5 O.Q3 0.1 0~07g4.3 - - -C~ 17.4 0.20 0.04 0.16 - - ~2.2 MoE~ 10.0 O.05 0.02 0.2 - O.03 - 8g.7 'rable 2 Met~l Purlt~ Mat~l Purity powder wt96 powder wt%
W 99 . 95 Fe 99 . 69 Cr 99 . 75 Cu 99 . 9 Nl 9g . 75 CO 99 . 87 t ~a~ 3 Table 3 Sampl~ Composltlon ( wt96 ) W~ ~unt of No. ratio compl~x B W Cr N1 Fe C~l Co borlde ( wt% ) 3.0 51.4 ~ bsl. l.0 71 2 1.9 35.5 15.0 - - - bal. l.1 44 3 1.9 42.0 10.0 - - - ~al. 1.3 44 4 2.2 29.9 15.0 - - - bBl. 0~8 41 3 . 053 . ~15, O - _ - bal . 1. 05 ~0 6 2.0 34.3 21.0 5.0 - - bal. 1.0 46 7 3.8 S8~2 5.0 1.0 - - bal. 0.9 80 a 1.7 29.1 21.0 S.0 5.0 - bal. l.0 39 9 2.5 46.8 10.0 10.0 û.2 - bal. 1.1 58 1.9 33.5 10.0 3.0 - 2.0 bsl l.0 44 /
~able 4 Ssmple Compo~itlon (wt96 ) W/E3 Amount of No, ratlo co~pl~x B W Cr N~ Fe Mo Co bor~d~ ( wt~ ) 11 2.4 2a.6 7.0 - - - bal. 0.7 39 12 3.0 51.4 5.0 - 15.0 - bal. ~.0 70 13 3.0 - 21.0 5.0 26.9 bal. - MoCoB 45 lg 4.0 - 17.1 10.0 bsl.33.7 - - Mo2FeB2 5 ~r~~~7 ~3 Table S
Sample WB W Cr tJi F~ Cu CrE3 Cc~
No. wt96 wt96 wt% wt% wt% wt~ wt% wt%
54.5 ~ 45.5 234.53.(~15.0 ~ 7~5 :~34.5 g.510.0 - ~ - -46.0 431.7 - 12.g - - - 2.652.8 554.5 2.05.0 - - - -38.5 636.4 - 21.0 5.0 - - -37.6 761~7 - ~.0 1.0 - - 2.431.9 830.9 - 21.0 ~ 0 5.0 - -3g.1 945.5 3.910.0 10.0 0.2 - -30.~
1034.5 - 10.0 3.0 - 2.0 -5~.5 Tabls 6 Sample WB W Cr Ni Fe MoB C:r~3 CO
No. wt% wt~ wt~ wt% wt~6 wt% wt% w~g6 1130.3 - 3.5 - - - 4.262.0 1254.5 - 5.0 - 15.0 - -25.5 13 - - 21.0 5.0 - 30.0 -44.0 14 - - 16.0 10.0 35.137.6 1.3 Table 7 Sample Transverse Hardness Transverse Oxidation No. rupture rupture weight strength strength gain (RT, GPa) (RA) (soooc~ GPa) (mg/mm2/h) 1 1.95 82.7 1.79 9.76 2 3.08 79.2 1.90 0.84 3 2.67 79.2 1.94 1.27 4 2.24 78.3 1.95 0.42 2.29 84.5 1.97 4.24 6 2.01 77.9 1.80 0.84 7 1.85 89.5 1.71 3.18 8 2.56 76.2 1.83 0.84 9 2.46 80.8 2.03 1.15 2.70 78.0 1.81 1.39 Table 8 Sample Transverse Hardness Transverse Oxidation No. rupture rupture weight strength strength gain (RT, GPa) (RA) (goo~c, GPa) (mg/mm2/h) 11 1.63 81.6 1.42 6.37 12 2.31 85.5 1.63 13.9 13 1.81 78.7 1.28 1.63 14 1.93 79.1 1.39 20.4
When the W/B ratio is within the range of 0.75 to 0.135 x (11.5-X), where X indicates the content of boron by weight percent, even if the above third phase is formed, the third phase will little affect the strength of the hard alloy; i.e., there would be an allowable decrease in the strength.
In the case where the W/B ratio is larger than 1, part of excess tungsten will be solid solute into the cobalt base alloy matrix phase, which will strengthen the matrix phase, thus improving the mechanical properties of the heat-resistant sintered hard alloy. ~owever, since the amount of the cobalt base alloy matrix phase decreases with the increase of the amount of the WCoB
type complex boride, it is necessary to decrease the amount of said excess tungsten in the matrix phase accompanied by the above increase, so as to maintain the strength of the hard alloy.
For the above reason, it is preferable that the upper limit of the amount of tungsten be 1.35 in terms of the W/B ratio in the case where the amount of boron is lowest (1.5% by weight), and 1 in terms of the W/B ratio in the case where the amount of boron is highest (~.1% by weight). This range is represented by the formula ,, , 2~
0.135 x (11.5-X), in which X is the weight percent of boron.
Accordingly, it is desirable that the amount of tungsten in the hard alloy be in the range of from 0.75 to 0.1~5 x (11.5-X), preferably in the range of 0.~ to 0.135 x (11.5-X) in terms of the W/B ratio; that is, from 19.1 to 69.7% by weight, preferably from 20.4 to 69.7% by weight, in said hard alloy.
In the case of a sintered hard alloy containing chromium, it is presumed that chromium will be solid solute into the WCoB type complex boride, and form a (wxcoycrz)s multiple boride of the WCoB
type complex boride, in which cobalt rather than tungsten is replaced partially by chromium and x + y + z is equal to 2, and further chromium will be solid solute into the cobalt base alloy matrix also, so that the resistances to corrosion, heat and oxidation of the sintered hard alloy will be improved.
Furthermore, chromium refines the (WxCoyCrz)8 multiple boride pha6e and improves the mechanical properties of the sintered hard alloy. With a content of chromium below 1% by weight, the above-mentioned improvement can not be attained, and with the content of chromium above 25% by weight, the mechanical properties of the 6intered hard alloy are remarkably decreased due to the generation of a brittle phase such as a CoCr sigma (a) phase. Accordingly, it is preferable that the content of chromium be from 1 to 25% by weight.
2~2~3 ,........................................................................ .
.
In the case of a sintered hard alloy containing nickel, it is presumed that nickel will substitute for cobalt and be solid solute into the co~alt base alloy matrix phase, and improve the mechanical properties, corrosion resistance and heat-resistance of the hard alloy. With the substitution of nickel below 0.2% by weight of cobalt content, the aforementioned improvements of mechanical ~' properties and the like can not be attained, and with the substitution of nickel above 30% by weight of cobalt, abrasion resistance is reduced due to the decrease of hardness.
Accordingly, it i5 preferable that nickel substitute for cobalt in the range of 0.2 to 30 % by weight of cobalt content.
Iron substitutes mainly for cobalt in the WCoB type complex boride and the cobalt base alloy matrix phase, and improves the strength at low temperature. With the substitution of iron below 0.2% by weight of cobalt content, the aforementioned improvement is not attained, and with the substitution of iron more than 15%
by weight of cobalt content, the hard alloy becomes less resistant to corrosion, heat and oxidation. Accordingly, in the case of the sintered hard alloy containing iron, it is preferable that iron substitute for cobalt in the range of 0.2 to 15% by weight of cobalt content.
Copper substitutes for cobalt and is solid solute into the cobalt base alloy matrix phase, and improves the corrosion ~esistance and heat c~nductivity of the sintered hard alloy. With the substitution of copper below 0.1% by weight of cobalt content, :, _ g _ Z~7.~3 the above improvements are not attained, and with the substitution of copper more than 7.5% by weight o~ cobalt content, the mechanical properties and heat-resistance are degraded.
Accordingly, it is preferable that copper substitute for cobalt in the range of 0.1 to 7.5% by weight of cobalt content, when copper is added to the sintered hard alloy.
The unavoidable impurities contained in the sintered hard alloy are mainly silicon, aluminum, manganese, magnesium, phosphorus, sulfur, nitrogen, oxygen, carbon or the like, and it is desirable that the content of these impurity elements be as little as possible. However, in the case where the total amount of these impurity elements is less than 1.0% by weight, the detrimental effects thereof to the properties of the sintered hard alloy are relatively small. Accordingly, it is preferable that the total content of the unavoidable impurities be less than 1.0% by weight, more preferably less than 0.5% by weight.
In the case where the sintered hard alloy is employed for a wear-resistant coating in which the strength is not of critical importance, and silicon and aluminum or the like are added intentionally so as to improve the oxidation resistance of the coating, the total content of the aforementioned elements may be over 1.0% by weight.
The sintered hard alloy is made by mixing boride powders of tungstel~, cobalt, chromium, nickel and iron; alloy powders of boron, with at least one of tungsten, cobalt, chromium, nickel, iron and copper; or boron powder and metal powders of tungsten, cobalt, chromium, nicXel, iron and copper, or alloy powders containing at least two of these metallic elements, thereafter wet milling the mixture with an organic solvent by means of a vibrating ball mill or the like, drying, granulating, and forming, followed by liquid phase sintering of the green compact in a non-oxidizing atmosphere such as in vacuum, a reducing gas, or an inert gas.
The hard phase, that is the WCoB type complex boride of the sintered hard alloy, is formed by the reaction during sintering.
A powder mixture obtained by blending metal powders such as cobalt, chromium and nickel to form the Co base alloy matrix phase, with the WCoB type complex boride such as WCoB and (WxCoyCrz)B which are prepared by reacting tungsten boride, cobalt boride, boron powder with metal powders such as tungsten, cobalt and chromium etc. in a furnace in advance, may be employed as the raw material powders also.
The liquid phase sintering is usually carried out at the temperature range of 1100 to 1400~C and for 5 to 90 minutes depending on the composition of the hard alloy. A hot press method, a hot isostatic pressing method, and an electric resistance sintering method or the like ma~ be also employed.
EXAMPLES
The compound powders listed in Table 1 and metal powders listed in Table 2 were blended in the compositions shown in Table 3 with the blending ratios shown in Table 5. The blended powders were wet milled with acetone by means of a vibrating ball mill for 28 hours and then dried and granulated. The powders thus obtained were pressed into a predetermined shape. The green compacts were sintered at the temperature of 1150 to 1300~C for 30 minutes in vacuum.
The transverse rupture strength and Rockwell A.
scale hardness (RA) at room temperature, the transverse rupture strength at 900~C, and the weight gain by oxidation after holding at the temperature of 900~C for 1 hour in still air of the samples of the hard alloys thus obtained are shown in Table 7.
Sample Nos. 1 to 10 all show extreme hardness ~and high transverse rupture strength at room temperature as well as high transverse rupture strength and excellent oxidation resistance at the high temperature. A hot extruding die was prepared using the hard alloy of sample No. 6, and a pure copper rod was extruded through the die. It was possible to extrude the rod 50 to 100 times satisfactorily. A similar die formed with a WC-Co type hard alloy could not be used practically for the pure copper rod hot extrusion.
COMPARATIVE EXAMPLES
The compound powders listed in Table 1 and the metal powders listed Table 2 were blended in the composition shown in Table 4 with the blending ratios shown in Table 6.
The hard alloys were prepared by the same method as shown in the EXAMPLES, and the properties thereof are shown in Table 8.
Sample No. 11 has a W/B ratio less than 0.75, and exhibits low transverse rupture strength at room temperature as well as the high temperature. Sample No. 12 exhibits low transverse rupture strength at the high temperature and poor oxidation resistance due to the content of iron being higher than 10% by weight, though it shows high transverse rupture strength at room temperature. Sample No. 13, containing a MoCoB type complex boride instead of the WCoB
type complex boride, exhibits low transverse rupture strength at room temperature as well as the high temperature, compared with the 6amples of EXAMPLES ha~ing approximately the same hardness. Sample No. 14 containing a Mo2FeB2 type complex boride exhibits low transverse rupture strength at high temperature and po~r oxidation resistance.
A similar hot extruding die as described in the EXAMPLES was prepared using the hard alloy of Sample No. 14, and a copper rod was extruded in the same manner as in the case of the EXAMPLES.
~nly 5 to 10 times extruding was possible with the die.
T~ble 1 Compound ~3 C N ~ W Fe . Cr Mo powder wt% wt% wt% wt96 wt% wt% w t% wt~
WB 5.5 O.Q3 0.1 0~07g4.3 - - -C~ 17.4 0.20 0.04 0.16 - - ~2.2 MoE~ 10.0 O.05 0.02 0.2 - O.03 - 8g.7 'rable 2 Met~l Purlt~ Mat~l Purity powder wt96 powder wt%
W 99 . 95 Fe 99 . 69 Cr 99 . 75 Cu 99 . 9 Nl 9g . 75 CO 99 . 87 t ~a~ 3 Table 3 Sampl~ Composltlon ( wt96 ) W~ ~unt of No. ratio compl~x B W Cr N1 Fe C~l Co borlde ( wt% ) 3.0 51.4 ~ bsl. l.0 71 2 1.9 35.5 15.0 - - - bal. l.1 44 3 1.9 42.0 10.0 - - - ~al. 1.3 44 4 2.2 29.9 15.0 - - - bBl. 0~8 41 3 . 053 . ~15, O - _ - bal . 1. 05 ~0 6 2.0 34.3 21.0 5.0 - - bal. 1.0 46 7 3.8 S8~2 5.0 1.0 - - bal. 0.9 80 a 1.7 29.1 21.0 S.0 5.0 - bal. l.0 39 9 2.5 46.8 10.0 10.0 û.2 - bal. 1.1 58 1.9 33.5 10.0 3.0 - 2.0 bsl l.0 44 /
~able 4 Ssmple Compo~itlon (wt96 ) W/E3 Amount of No, ratlo co~pl~x B W Cr N~ Fe Mo Co bor~d~ ( wt~ ) 11 2.4 2a.6 7.0 - - - bal. 0.7 39 12 3.0 51.4 5.0 - 15.0 - bal. ~.0 70 13 3.0 - 21.0 5.0 26.9 bal. - MoCoB 45 lg 4.0 - 17.1 10.0 bsl.33.7 - - Mo2FeB2 5 ~r~~~7 ~3 Table S
Sample WB W Cr tJi F~ Cu CrE3 Cc~
No. wt96 wt96 wt% wt% wt% wt~ wt% wt%
54.5 ~ 45.5 234.53.(~15.0 ~ 7~5 :~34.5 g.510.0 - ~ - -46.0 431.7 - 12.g - - - 2.652.8 554.5 2.05.0 - - - -38.5 636.4 - 21.0 5.0 - - -37.6 761~7 - ~.0 1.0 - - 2.431.9 830.9 - 21.0 ~ 0 5.0 - -3g.1 945.5 3.910.0 10.0 0.2 - -30.~
1034.5 - 10.0 3.0 - 2.0 -5~.5 Tabls 6 Sample WB W Cr Ni Fe MoB C:r~3 CO
No. wt% wt~ wt~ wt% wt~6 wt% wt% w~g6 1130.3 - 3.5 - - - 4.262.0 1254.5 - 5.0 - 15.0 - -25.5 13 - - 21.0 5.0 - 30.0 -44.0 14 - - 16.0 10.0 35.137.6 1.3 Table 7 Sample Transverse Hardness Transverse Oxidation No. rupture rupture weight strength strength gain (RT, GPa) (RA) (soooc~ GPa) (mg/mm2/h) 1 1.95 82.7 1.79 9.76 2 3.08 79.2 1.90 0.84 3 2.67 79.2 1.94 1.27 4 2.24 78.3 1.95 0.42 2.29 84.5 1.97 4.24 6 2.01 77.9 1.80 0.84 7 1.85 89.5 1.71 3.18 8 2.56 76.2 1.83 0.84 9 2.46 80.8 2.03 1.15 2.70 78.0 1.81 1.39 Table 8 Sample Transverse Hardness Transverse Oxidation No. rupture rupture weight strength strength gain (RT, GPa) (RA) (goo~c, GPa) (mg/mm2/h) 11 1.63 81.6 1.42 6.37 12 2.31 85.5 1.63 13.9 13 1.81 78.7 1.28 1.63 14 1.93 79.1 1.39 20.4
Claims (3)
1. A heat-resistant sintered hard alloy containing 35 to 95% by weight of a WCoB type complex boride in a cobalt base alloy matrix phase, wherein said hard alloy consists of 1.5 to 4.1% by weight of boron, 19.1 to 69.7% by weight of tungsten, the balance being cobalt and a maximum of 1%, by weight of the alloy, of unavoidable impurities.
2. A heat-resistant sintered hard alloy containing 35 to 95% by weight of a WCoB type complex boride in a cobalt base alloy matrix phase, wherein said hard alloy consists of 1.5 to 4.1% by weight of boron, 19.1 to 69.7% by weight of tungsten, 1 to 25% by weight of chromium, the balance being cobalt and a maximum of 1%, by weight of the alloy, of unavoidable impurities.
3. A heat-resistant sintered hard alloy containing 35 to 95% by weight of a WCoB type complex boride in a cobalt base alloy matrix phase, wherein said hard alloy consists of 1.5 to 4.1% by weight of boron, 19.1 to 69.7% by weight of tungsten, 1 to 25% by weight of chromium, the balance being cobalt and a maximum of 1%, by weight of the alloy, of unavoidable impurities, and further comprises at least one of nickel, iron and copper, wherein nickel substitutes for cobalt in the range of 0.2 to 30% by weight of cobalt content, iron substitutes for cobalt in the range of 0.2 to 15% by weight of cobalt content and copper substitutes for cobalt in the range of 0.1 to 7.5% by weight cobalt content.
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| CA 2060723 CA2060723C (en) | 1992-02-05 | 1992-02-05 | Heat-resistant sintered hard alloy |
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| CA2060723C true CA2060723C (en) | 1998-08-04 |
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