The Structure and Phase Composition Acquired by Fe-Ti-Ni-C Alloys in Thermal Synthesis

The structure and phase composition of Fe-Ti-Ni-C alloys produced in situ by thermal synthesis at 1200 degrees C using TiH2, Fe, graphite, and Ni powder mixtures have been studied. The synthesized alloys represent a skeleton of titanium carbide grains of different stoichiometry, with sizes varying from 0.5 to 16 mu m, surrounded by metal reinforcement layers. The starting mixtures without nickel or with 5% Ni have coarse TiC grains. When Ni content of the mixture increases to 10-20%, the maximum grain size sharply decreases to 6-7 mu m. The microhardness of the synthesized alloys decreases when nickel amount in the mixture increases to 15% but becomes somewhat higher at 20% Ni. The phase composition of the alloys substantially depends on the amounts of starting mixture components and includes titanium carbide, Fe3C cementite, alpha-iron solid solution, and intermetallic FeNi3(for ironcontaining mixtures) and Ni3Ti and Ni4Ti (for nickel-containing mixtures). When Ni content of the starting mixture increases to 10-20%, the lattice parameter and stoichiometry of TiC(x)slightly decrease and carbide particles noticeably refine. The thermally synthesized alloys have been ground to produce reinforced steel composite powders, which can find extensive application in depositing wear-resistant coatings and fabricating bulky parts by compaction followed by sintering, hot pressing, or hot forging.