RU2531332C2 - Tungsten carbide-based hard alloy (versions) - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to powder metallurgy, in particular, to tungsten carbide-based hard alloys. It can be used for manufacture of cutting tools. The hard alloy contains, wt %: cobalt - 3.5-5.3; iron - 1.4-3.2; cuprum - 0.8-1.0; the rest - tungsten carbide. The hard alloy contains, wt %: cobalt - 5.1-5.6; molybdenum - 1.8-2.5; titanium - 0.5-0.8; the rest - tungsten carbide.

EFFECT: alloy characterised by high hardness and wearing quality.

2 cl, 1 tbl, 2 ex

Description

The invention relates to powder metallurgy, and in particular to tungsten carbide-based carbides, and can be used to make a cutting tool.

Known hard alloy based on tungsten carbide with a cobalt bond doped with Al ₂ O ₃ oxide with a content of Al ₂ O ₃ (0.09-0.1)% (mass.), (5.91-19)% cobalt and (84 -80)% WC. Compared with base single carbide alloys of the VK group, alloys have a 10-15% increase in mechanical strength and 1.5-2.6 times increase in tool life when turning 1X18H9T steel and KhN56VMKRO alloy. The disadvantage is the complication of the alloy production technology due to the introduction of an additional processing operation for aqueous solutions of cobalt and aluminum chlorides in order to obtain a composite powder consisting of cobalt with dispersed inclusion of aluminum oxide (ed. St. SU No. 1673622, IPC С22С 29/08, 1991 g.).

An alloy based on tungsten carbide (70-85%, mass.) [RU No. 2338804, IPC С22С 1/08, 2008], containing (15-25)% α-Fe (magnetic alloy) or (17) as a binder -30)% alloy Fe: Ni (non-magnetic alloy), although it has high hardness, while maintaining high strength (σ = _mfd 1300-1480 MPa) may contain at grain boundaries of tungsten carbide η - phase (Fe ₂ W ₃ C), softening alloy, especially in conditions of shock loads.

Known sintered carbide based on tungsten carbide (wt.% 80-82) with a binder (wt.% 18-20) containing (48-50)% molybdenum, (1-2)% niobium, (10-12)% rhenium and (38-41)% cobalt; the alloy has high strength (σ _ar = 1950 MPa). In addition to the presence of scarce rhenium in the binder, the alloy contains in the binder an increased amount of molybdenum, which gives the alloy, along with strength, brittleness [patent RU No. 2351676, IPC С22С 29/08, 2009].

One of the ways to improve the quality of tungsten carbide-based carbide materials is the introduction of Ni ₃ Al intermetallide into the cobalt binder [Maslenkov SB, Gorshkova TI, Kudinova AA and other Hard alloys based on tungsten carbide with a plastic modified binder // Vestnik mashinostroeniya, 1994, No. 10. - S.27-30]. Nickel aluminide Ni ₃ Al, in comparison with β - Co, has the same type of crystal lattice (fcc); close values of lattice periods, density, hardness and linear expansion coefficients. As a result, the strength characteristics of alloys with Ni ₃ Al increase (σ _ar = 1300 MPa), heat resistance and wear resistance, therefore the WC + 10% Ni ₃ Al alloy is recommended for operation at high temperatures; for machining heat-resistant alloys by cutting is not applicable due to the low tensile strength in bending and compression.

Known compositions of hard alloys based on tungsten carbide, in which a binder of cobalt and rhenium is modified with chromium carbides Cr ₃ C ₂ (0.05-2)% [patent RU No. 2027791, IPC C22C 29 / 08.1995, alloy on WC base containing HfC, Ni, Co, Ce, La [patent RU No. 2012646, IPC C22C 29/08, 1994], as well as an alloy having hafnium oxide HfO ₂ in the carbide phase of the WC and cobalt as a binder, chrome and nickel [application RU No. 97111541 IPC С22С 29/08, 1999].

Known tungsten-cobalt hard alloy (82.6% WC + 8% Co) with additives in the carbide bond Cr ₃ C ₂ (0.8%), TiC (1.5%) and 1.5% Mo ₂ C. Fine-grained the structure of this alloy (85% carbide grains are up to 1 μm in size) with a porosity of 0.04-0.8 provides a hardness of HRA = 91.5 and σ _ar = 2227 MPa, while the effect of Mo ₂ C on the properties of the hard alloy is not indicated [ Pankov BC, Chuvilin AM, Falkovsky V.A. Technology and properties of sintered hard alloys and products from them. - M .: MISiS, - 2004. - P.261].

It is known that it is possible to obtain a single-phase solid solution through co-precipitation of tungsten and molybdenum salts and process according to the “oxide - metal - carbide” scheme. When W and Mo are sintered with carbon, in addition to the carbide phase (W, Mo) C, a second carbide phase (W, Mo ₂ ) C based on Mo ₂ C appears, which impairs the properties of the alloy. The alloy contains 10% cobalt binder, and the composition of the carbide phase varies in such ranges: W - from 80% (at) to 30% (at), and Mo - from 20 to 70% (at) [Pankov BC, Chuvilin AM, Falkovsky V.A. Technology and properties of sintered hard alloys and products from them. - M .: MISiS, - 2004. - p.283].

The closest to implementation is an alloy based on tungsten carbide containing 3.0-20.0 wt.% Binder, which includes 20-75 wt.% Co, up to 5 wt.% Mo, up to 5 wt.% Fe and etc. [(GB patent No. 1085041, C22C 29/06, 1967]. If the bond is 20% of the alloy composition, then the structure of the cobalt hard alloy may contain (4-15)%, molybdenum - up to 1% and iron - up to 1% .With a binder content of 3% in the alloy, these figures will respectively be equal to: (0.6-2.25)% for cobalt, up to 0.15% for molybdenum and up to 0.15% for iron .

Hardness experimental alloys ranges HRA = 93,2-94,0, and σ = _mfd 195-90 kg / mm ² [composition WC + (Co, Cr, Ni , W, C, B, Ti)]; alloys WC + (Co, Cr, Ni , W, C, B, V, Zr, Nb) - HRA = 93,6-93,8, σ _mfd = 108-130 kg / mm, but the bending strength of the alloys remains insufficiently high.

The technical result of the invention is to increase the hardness and, as a consequence, the wear resistance of a tungsten carbide based hard alloy.

The technical result is achieved in that a carbide based on tungsten carbide and a cobalt binder modified with iron and copper contains components in the following ratio, wt.%:

cobalt 3,5-5,3 iron 1.4-3.2 copper 0.8-1.0 Wolfram carbide rest

The difference between the proposed alloy from the prototype is the presence of copper instead of molybdenum in it and an increased iron content.

The technical result is also achieved by the fact that a carbide based on tungsten carbide and a cobalt binder modified with molybdenum and titanium contains components in the following ratio, wt.%:

cobalt 5.1-5.6 molybdenum 1.8-2.5 titanium 0.5-0.8 Wolfram carbide rest

The difference between the proposed alloy from the prototype is the presence in it of titanium instead of iron and an increased content of molybdenum.

The method for producing the alloy consists in mixing the components, their subsequent drying, pressing and sintering.

The following are examples of the invention.

Example 1

Experimental batches of alloys based on tungsten carbide with different amounts in a binder of cobalt, iron and copper were obtained and tested. The process of preparing carbide mixtures WC + (Co + Fe + Cu) is carried out in accordance with the basic technology for the production of products from VK8 alloy (WC - 92 wt.% And Co - 8 wt.%) And consists of:

- mixing tungsten carbide powders and binder components with simultaneous grinding in a liquid medium (distilled water) in ball mills;

- drying the mixture in a hydrogen atmosphere and sieving the carbide mixture;

- mixing the mixture with synthetic rubber dissolved in gasoline and drying the mixture to dry completely;

- pressing the resulting mixture into piles according to GOST 20019-74 and into plates of mold 02271 according to GOST 25395-90;

- sintering of products in a hydrogen atmosphere (according to the regime for VK8 alloy) and at temperatures of 1420 ° C and 1540 ° C.

In the experimental hard alloys, the iron content ranged from 1.4-5.0% by weight, the copper content 0.8-1% by weight, and the cobalt content 1.5-5.6% by weight. The physicomechanical properties of alloys of the WC - (Co - Fe - Cu) system are presented in Table 1 (batch 1), where, for comparison, the TU requirement for the VK8 alloy is given.

The performance of the experimental alloys was tested during longitudinal turning by cutters with plates of the form 0227 according to the STP 19.0-6-88 method. “Hard powder alloys and ceramics. Products for cutting tools. The method of testing the cutting properties ", M .: VNIITS, 1988.

The processed material is SCH25 cast iron, cutting modes: V = 2.9 m / s; t = 1 · 10 ^-3 m; S = 0.2 · 10 ^-3 m / rev; incisors geometry: γ = 0; α = 8 °; φ = 45 °; λ = 0, the allowable wear on the rear surface is h ₃ = 0.8 mm.

From the presented data it can be seen that when the Fe content is in the range of% masses 1.4-3.2, Cu in the range of 0.8-1.0% mass and Co in the range of 3.5-5.3% mass hardness and wear coefficient increase in comparison with VK8 alloy. An increase in resistance by 1.7-1.8 times (T = 1420 °) and 1.5-1.9 times (T = 1540 °) was obtained.

Example 2

Experimental batches of alloys based on tungsten carbide with different amounts in a bunch of cobalt, molybdenum and titanium were obtained and tested analogously to example 1.

In the experimental hard alloys, the cobalt content ranged from 3.4-5.6% by mass, the molybdenum content was 1.8-2.7% by mass, and the titanium content was 0.5-0.8% by mass. The physicomechanical properties of alloys of the WC - (Co - Mo - Ti) system are presented in Table 1 (batch 2).

From the presented data it is seen that when the Mo content is within% mass. 1.8-2.5, Ti in the range of 0.5-0.8% of the mass. and Co in the range of 5.1-5.6% of the mass. hardness and wear coefficient increase in comparison with VK8 alloy. Received an increase in resistance by 1.4-1.85 times (T = 1420 °) and 1.8-2.0 times (T = 1540 °). An increase in hardness by 3 HRA units was obtained for T = 1540 ° and the same hardness with VK8 alloy for T = 1420 °. With an increase in the Mo content of more than 3%, the alloy has greater brittleness and lower resistance coefficient compared to VK8 alloy.

Thus, the present invention allows to increase the hardness of the plates of the hard alloy and, as a consequence, the resistance of the cutting tool.

Table 1. No. of parties Alloy number Chemical suck, wt.% Physico-mechanical properties at sintering temperatures WC Co Mo Fe Cu Ti O ₂ 1540 ° C 1420 ° C ρ g / cm σ _ex MPa Hra Coer. power e Ct ρ g / cm ³ σ _ex MPa Hra Coer. power e Ct one 1.1 92.6 1,52 - 5.03 0.82 - 0.35 14.44 913 90.1 160 1.4 13.46 873 85.6 162 1,1 1.2 92.54 3.41 - 3.23 0.82 - 0.28 14.54 814 90.6 211 1,5 13.89 791 87.3 207 1.8 1.3 92.45 5.3 - 1.43 0.82 - 0.2 14.76 1505 90.0 116 1.9 14.49 1293 89.0 112 1.7 2 2.1 91.9 5.65 1.84 - - 0.61 0.16 14.21 1354 91.9 210 2.0 13.0 804 87.0 231 1.85 2.2 91.6 5.10 2.69 - - 0.61 0.17 14.10 1288 91.7 229 1.8 13.19 912 88.0 248 1.4 2.3 90.62 3.44 5.44 - - 0.6 0.20 13.26 646 88.4 234 X 13,4 422 73.7 214 0.9 Solid TU for VK8 (T = 1420 ° C) 92 7.5-8.0 - no more - - no more 14.5-14.8 ≥1700 ≥88.0 100-180 ≥1.0 0.3 0.5

Claims (2)

1. A carbide based on tungsten carbide, characterized in that it contains tungsten carbide and a cobalt binder modified with iron and copper, in the following ratio, wt.%:
cobalt 3,5-5,3 iron 3.2-1.4 copper 0.8-1.0 Wolfram carbide rest 2. A tungsten carbide-based carbide, characterized in that it contains tungsten carbide and a cobalt binder modified with molybdenum and titanium, in the following ratio, wt.%:
cobalt 5.1-5.6 molybdenum 1.8-2.5 titanium 0.5-0.8 Wolfram carbide rest