Ti based composites containing Si₃N₄ and TiN were produced by spark plasma sintering to develop wear resistant Ti based materials. Sliding tests were conducted by sliding the composite disk against a Si₃N₄ ball in dry atmospheres and in the liquids of n-hexane, water and ethanol. The wear of the composite was much smaller than that of Ti metal in the tests. Observations and elemental analyses of the worn surfaces revealed that water and ethanol prevented the adhesion while adhesive wear occurred in dry atmospheres and in n-hexane. The experimental results indicated the wear mechanism of the composite might be strongly dependent on the tribochemical reactions between the composite and species in the surroundings.