Reaction synthesis of ultrafine titanium diborides and nitrides reinforced steel matrix composites in situ by spark plasma sintering

Abstract

A novel technique for synthesis of in situ titanium diborides and nitrides reinforced steel matrix composite (TiB2–TiN/Fe) was put forward. In situ TiB2–TiN/Fe composite was synthesised by spark plasma sintering of mechanically mixed ferrotitanium and boron nitride (BN) powders. The phase evolution during sintering indicates that the TiB2–TiN reinforcements are formed in situ as follows: first step, the solid/solid interface reaction between ferrotitanium and BN, resulting in the formation of a small amount of TiB2 and TiN below 1000°C; second step, the solid–liquid solution precipitation reaction in the Fe–Ti–B–N system, resulting in most of TiB2 and TiN reinforcement formation at ∼1100°C. The microstructure investigation reveals that utrafine TiB2 and TiN reinforcements with a size of ∼1 μm are homogeneously distributed in the Fe matrix.