Comparative wear behaviour of Ni-Cr-B-Si hardface coatings made by cold metal transfer and plasma transfer Arc welding processes

Ni-Cr-B-Si hardface coating plays an important role in the mating components of nuclear power plants. Obtaining a crack-free coating with low dilution and optimum hardness is essential for reactor applications. In general, it is difficult to achieve this through conventional high heat input processes. In this work, Ni-Cr-B-Si hardface coating was successfully developed on 316LN stainless steel substrate by Cold Metal Transfer (CMT) welding process using metal-cored filler wire. Moreover, for comparative analysis, Ni-Cr-B-Si hardface coating was deposited using Plasma Transferred Arc (PTA) process. The obtained coatings were characterised for their microstructure, hardness, and wear behaviour. Results revealed higher hardness and lower specific wear rate of hardface coating made by the CMT process compared to the coating made by the PTA process. The superior behaviour of the CMT coating obtained may be due to its low dilution compared to the coating made using the PTA process. Confocal microscopy on the worn pins revealed abrasive and adhesive wear as a dominant mechanism in the CMT and PTA coatings, respectively. This study concluded that CMT could be used as an alternate potential process for depositing a crack-free hardface coating with superior wear behaviour.