Тhe element-phase composition and properties of the surface layers of carbide-tipped tools made of TK and WC-Co alloys

E.E. Bobylyov, A.G. Sokolov
Received: 03 April 2017; Revised: 13 June 2017; Accepted: 15 June 2017
This paper is written in Russian
Citation: E.E. Bobylyov, A.G. Sokolov. Тhe element-phase composition and properties of the surface layers of carbide-tipped tools made of TK and WC-Co alloys. Letters on Materials, 2017, 7(3) 222-228
BibTex   DOI: 10.22226/2410-3535-2017-3-222-228

Abstract

A technology for the deposition of diffusion titanium coatings from liquid metal media on hard alloys of TK (WC+TiC+Co) and VK (WC+Co) systems is described. It is shown that the diffusion saturation of hard alloy tools of these types by titanium from the Pb-Bi-Li melt in a temperature range 1000-1100°С and subsequent heat treatment results in a seven-fold increase of the wear resistance of the tools due to the formation of a diffusion coating. The thickness of the coatings varies depending on the temperature and deposition time and ranges from 2.6 to 6 μm on TK alloys and from 2 to 5.4 μm on VK alloys. The coatings consist of two layers, the surface one and transition one. The results of elemental and metallographic analyses are presented. The microhardness of a coating on hard alloy T15K6 is about 30000 MPa and on the hard alloy WC-8Co is 25000 MPa. The high microhardness of the coatings is caused by their formation on the basis of titanium carbide TiC, while other elements are driven depthward the material to coat. It has been found that the elemental composition of the coatings depends on the composition of the hard alloy under coating. The concentration of titanium in the surface layer of the tool amounts 87.6 % for VK alloys and 93 % for TK alloys. The transition layer is characterized by approximately equal concentrations of titanium and tungsten (about 20 to 25 %) and a reduced microhardness. The diffusion coatings are characterized by a smooth change of the concentration of elements with depth and good adhesion to the base material.

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