Degradation of components that operate under elevated temperature and carburizing environments involves the diffusion of C and the precipitation of carbides. Industries have been seeking for materials that can withstand these service conditions. The present work aimed to develop coatings to address this challenge through the enrichment of a Ni based alloy with Al. An atomized Ni alloy without Al and different powder mixtures with 15 and 30wt%Al were deposited by PTA on a carbon steel. Coatings were analyzed in the as deposited condition and after temperature exposure in an air furnace and pack cementation tests at 650º and 850ºC. Vickers microhardness profiles under a 500gf load, X-ray diffraction, optical and scanning electronic microscopy were done Results revealed that the presence of Al lead to the development of a complex intermetallic phases which were associated with the enhanced metallurgical stability of the coatings under the tested temperatures. The superior performance of the coatings deposited with the powder mixture containing 30wt%Al after pack cementation was associated with the development of the NiAl intermetallic phase and of the oxide layer Al 2 O 3 that stabilized the microstructure at the tested temperatures and reduced the diffusion of C.

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.