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°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 μm, 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 μm. 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, α-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.