Structure and properties of the modified processing zone of plazma treatment of threaded cutters with solid alloys plates

This paper presents a study of the structure, hardness, and the crystal structure parameters in a modified zone of thread-cutting cutters with soldered carbide inserts of the VK8 and T5K10.alloys. The character of the interphase boundaries melting, metallographic and X-ray diffraction studies on plasma jet high-concentration heating and high-speed cooling of thread-cutting cutters has been shown. The analysis of these factors shows good promise in applying the surface hardening method in order to improve the performance of a thread-cutting tool with carbide-tipped plates. At the same time, due to the complex profile working surface, the use of any hardening methods presents difficulties. Under these conditions, phase and structural transformations, that differ from each other, can take place in different parts of the modified zone. The highest performance properties and dis-persed structure are obtained on plasma treatment of hard alloys without melting, but with phase transformations in carbides and the binder. Optimum modes of plasma treatment ensure that very kind of hardening in hard alloy volumes adjacent to the cutting edges. The main process determining the nature of phase and structural transformations in hard alloys under plasma modification is contact melting of carbide grains; it depending on two factors - the wettability of the carbides with the liquid binding phase and the solubility of the bound carbides which results in the crushing of similar (primary) carbide grains, saturation of the binder with tungsten and carbon and dispersion hardening of the bond resulting from the secondary dispersed carbides separation. Along with the grinding of the initial carbide grains, the supersaturated solid solution W and C in Co decomposes, with the release of dispersed secondary carbides. The melted grains of the primary carbides have an irregular shape and "loose" edges, and the grains of secondary carbides precipitated as a result of the precipitation hardening are mainly rounded