CHARACTERISTICS OF THE FORMATION OF THE STRUCTURE AND PROPERTIES OF A MEDIUM-GRAINED HARD ALLOY WITH A NICKEL BINDER (92% WC + 8% Ni) SINTERED IN VACUUM AT A TEMPERATURE OF 1350 ОС UNDER THE DIFFERENT VALUES OF THE EXTERNAL UNIAXIAL COMPRESSION

Abstract

The possibilities of further improvement of the operational characteristics of the low-nickel hard alloy 92% WC-8% Ni by using various methods of sintering intensification are described. It is claimed that the directed placement of large grains of tungsten carbide (WC) can provide anisotropy of alloy properties, the use of which will increase the operational characteristics of the product. Systematic studies of the effect of compression on the specifics of the change in the properties of the alloy, including due to the change in the nature of the distribution of WC grains in the volume of the product, has not been carried out yet. In our opinion, the lack of such knowledge does not allow to create in advance hard alloy products with increased properties and due to the optimal distribution of the carbide component in their volume.

Therefore, the purpose of this study is to determine the influence of uniaxial compression on the nature of the distribution of the components of a hard alloy with a nickel bond, which will generally ensure an increase in the level of its properties.

The paper presents the results of a study of the peculiarities of the formation of the structure and properties of the medium-grained hard alloy VN8 during sintering in a vacuum at a temperature of 1350 °C under different values ​​of external uniaxial compression from 0 MPa (free sintering) up to 0.6 MPa (0.4, 0.6).

The work describes in detail the method of researching the alloy and obtaining samples.

Standard values ​​of alloy properties are determined.

It was established that the structural state of the VN8 hard alloy sintered in a vacuum without the application of uniaxial pressure and under the action of external pressure stress does not change with increasing compressive stress. The average cross-sectional size of WC grains was decreased. The reason for the decrease in the cross-sectional size of WC grains from 1.46 μm to 1.39 μm is that during sintering, the mass of the alloy moves under the action of compressive stress. This does not allow for conglomerates of carbide grains to appear in the alloy.

Under the influence of pressure during the sintering process, the structure of the alloy becomes texturized, random individual oriented groups of WC grains appear. Obviously, an increase in the sintering temperature will ensure an increase in the texturization of the alloy structure.

It has been shown that the sintering method is quite promising for the production of structural hard alloy products