Evaluation of intermetallic coatings processed by PTA

Plasma Transferred Arc hardfacing (PTA) is an excellent tool for surface tailoring as it allows for the manipulation of coatings chemical composition. In particular in-situ alloy development can be achieved during the deposition of different powder mixtures. In this work powder mixtures of Ni-Al, Nb-Al and Fe-Al were deposited by PTA. Coatings were characterized for their mechanical features at room temperature evaluated by Vickers microhardness under 300gf load, nano(0,04gf) and macro(10kgf) scratch tests and pin-on-abrasive disc tests under 1kgf. Results showed very high dilution for the processed coatings with Vickers microhardness varing with the chemical composition of the deposited powder, mixtures, with the Fe based deposits exhibiting the lower hardness (below 400Hv) and the Nb-based deposits reaching 900HV. Scratch hardness followed Vickers micro hardness only for the Nb based coatings. Abrasion mechanism also varied for each alloy system and within each alloy system, the harder the coating the better the abrasive wear resistance. However when comparing the full set of coatings the Nb based coatings exhibited a superior performance and the Ni based deposits the poorer wear resistance.