Influence of aluminium on the microstructure of Co based alloy coatings

Abstract

Coating contamination as a consequence of the diffusion of elements from the operating environment, accounts for the deterioration of a variety of mechanical components, and is particularly severe on those that operate at elevated temperatures. This study analysed the degradation of three Co based alloy coatings as a consequence of their contamination with Al. One Co–Cr–W and two Co–Cr–Mo–Si atomised alloy coatings, each with and without 5 wt-% aluminium powder, were deposited by plasma transferred arc on AISI 316L stainless steel plates. Accelerated aging at 600 and 1000°C contributed to the understanding of the effect of Al on the microstructure of coatings. Coatings with and without Al were characterised by laser confocal microscopy and microhardness. Dilution increased on coatings modified with Al due to the exothermic synthesis of aluminide compounds and the most significant microstructure modification was observed in the Co–Cr–Mo–Si coatings as primary Laves phase was almost suppressed. Accelerated ...