Method for eliminating WC (Wolfram Carbide) grain fragmentation at phase boundary between ultra-coarse grain hard alloy and super-coarse grain hard alloy

Abstract

The invention discloses a method for eliminating WC (Wolfram Carbide) grain fragmentation at the phase boundary between ultra-coarse grain hard alloy and super-coarse grain hard alloy. Mechanical activation is conducted on WC powder, so that WC is reactivated and crumbly areas of WC particles are peeled off; water-phase normal-pressure reduction and follow-up thermal diffusion processes are adopted to prepare compact Co / Ni coated WC-type composite powder, so as to adjust the solution or the deposition of WC during the liquid-phase sintering process of the alloys, which eliminates the WC grain fragmentation at the phase boundary of the alloys and improves the performances of the alloys. The water-phase normal pressure reduction is conducted for reducing a Co / Ni hydroxide water-based slurry under a normal pressure by taking the WC as the core of heterogeneous nucleation, so as to prepare a WC-type composite powder which adopts a flower-shaped nano package assembly and is coated with a Co / Ni layer. The thermal diffusion is conducted by diffusing and homogenizing the composite powder prepared through water-phase reduction by utilizing a nano diffusion and sintering effect, so as to form the WC-type composite powder coated with a compact Co / Ni layer.

Description

technical field [0001] The invention relates to a method for eliminating the breakage phenomenon of WC crystal grains at the phase boundary of ultra-coarse and ultra-coarse-grained hard alloys. Background technique [0002] Cemented carbide is produced by powder metallurgy and consists of transition group refractory metal compounds (WC, TiC, TaC, NbC, etc.) and bonding metals (Co, Ni, Fe, etc.), with a hard phase + bonding Engineering composites with phase structure characteristics. During the sintering process, the cemented carbide forms a liquid phase through eutectic reaction, and the sintering of cemented carbide is a typical liquid phase sintering. The binder phase of cemented carbide is a solid solution of transition metals such as C and W, which is based on the binder metal. [0003] According to the classification standards of cemented carbides of Sandvik, the largest cemented carbide manufacturer in the world, cemented carbides with WC grain sizes of 3.5 μm to 4.9...

AI Technical Summary

Problems solved by technology

Methods such as CVD, Sol-Gel, and polyol liquid phase reduction have problems such as high preparation costs

Electroless plating and electroplating have problems such as easy introduction of foreign impurities, and as raw materials for cemented carbide production, they must meet the requirements of high purity

In addition, there are many reports on tungsten-cobalt double salt precipitation, spray drying to prepare tungsten-cobalt composite oxide, and direct reduction carbonization to prepare WC-Co composite powder, but this composite powder is only suitable for the preparation of ultrafine cemented carbide.

Images