STRUCTURE AND PROPERTIES OF CHROMIUM CARBIDE 65 wt.% Fe–35 wt.% FKh800 STEEL DOPED WITH TITANIUM BORIDE ADDITIONS

Abstract

The effect of TiB₂ additions on the structure, phase composition, mechanical and tribological properties of materials in the Fe–FKh800 system was studied. The introduction of titanium diboride additions activated compaction of the iron-based composites through sintering with participation of the liquid phase that emerged with the formation of low-melting Fe–C–B (Т_m ~ 1050 ºC) and γ-Fe–Fe₂B–TiB₂ (Т_m ~ 1162) eutectics and led to a 50–70 ºС decrease in the sintering temperature of the compacts. Titanium boride additions between 0.38 to 0.74 wt.% provided 20–25% higher bending strength of the 65 wt.% Fe–35 wt.% FKh800 composite with a slight increase in hardness. Metallographic studies, X-ray diffraction, and electron microprobe analysis of the Fe–35 wt.% FKh800–TiB₂ materials showed that titanium boride additions promoted a multiphase and microheterogeneous structure of the matrix-reinforced composite, consisting of Kh17 chromium steel, double M₇C₃ and M₃C iron–chromium carbides, and complex Me₃ (CB) carboborides. The influence of TiB₂ additions on the wear resistance of the composites subjected to the action of fixed diamond wheel particles and to dry friction against ShKh15 steel was studied. The studies showed that the abrasive mass wear (I_m) of carbide steels decreased from 36.94 to 14.8 mg/km and their linear wear (I_l) decreased from 0.197 to 0.079 mm/km with TiB₂ additions increasing from 0.38 to 1.48 wt.%. Titanium boride additions ranging from 0.38 to 2.2 wt.% reduced the mass wear rate from 4.9 to 1.9 mg/km in dry friction of the composite against a ShKh15 counterface with 50–55 HRC hardness and decrease the friction coefficient from 0.49 to 0.38.