Microstructure and tribological behaviour of TiC-Ni-CaF2 composite coating produced by TIG cladding process

TiC-Ni-CaF2 self-lubricating composite coating has been deposited on AISI-304 steel substrate by TIG cladding process using powder mixture of TiC, Ni and CaF2. Effect of CaF2 percentage in the precurser has been emphasized for metallurgical and mechanical characteristic of the produced coating. Owing to the fluxing effect of CaF2, heat accumulation in the coating zone augmented and solid lubricant behaviour of CaF2 improved the tribological properties of the coating. SEM and EDS analysis of the coating revealed that processing current and CaF2 percentage in the precursor have a significant influence on the microstructure and corresponding mechanical properties of the coating. Based on the heat input, which is synergic effect of processing current and CaF2 content, dilution of the coating material in steel matrix altered and consequently the microhardness and corresponding wear properties of the coating varied. Sliding abrasive wear test performed against alumina abrasive disc show that wear rate of the composite coating expressively governed by the processing condition of the coating. Further, to assess the coefficient of friction (COF) of the coating sliding wear test have been performed against hardened steel disc, which clearly exhibited that with the increase in CaF2 percentage in the precursor, COF significantly reduced.