Obtaining fine-grained hard alloys homogeneous in carbide grain

Abstract

The actual task of this work is to obtain homogeneous hard alloys with fine carbide grains, combining high hardness and strength. Studies were carried out to establish the most favorable phase compositions of hard alloys and the most rational technical methodology for their production. In this research work, a nanostructured WC-TiC-Co powder charge was obtained by mechanochemical synthesis. Nanosized WC powder and nanopowder with precipitated Co were added to the hard alloy charge by mixing in a ball planetary mill. The process of pressing the powder charge at a pressure of 100-1000 MPa, as well as the sintering process at a temperature within the range of 1450-1600℃ was applied. The chemical-metallurgical method of deposition of metal layers from salt solutions was applied to obtain the WC-Co hard alloy. X-ray structural analysis and scanning electron microscopy were applied. The effect of the preparation method on the phase composition of WC-TiC-Co consolidated samples was studied. In the microstructure of these hard alloys, intercrystalline particles of (Ti,W)C are observed, and the presence of the liquid phase can lead to a rounded shape. It was found that the addition of nano-sized WC powder leads to an increase in pressed density. It was revealed that the addition of WC nanosize additives or WC nanopowder with deposited cobalt makes it possible to obtain a fine-grained structure with a grain size of not more than 4-6 microns. It was found that the addition of WC nanopowder with precipitated cobalt to the alloy has the highest Brinell hardness values; in addition, it leads to an increase in the bending strength.