Assessing the resistance of metal matrix composites and their microstructural integrity under erosion–corrosion

Materials and machinery components handling corrosive slurries are exposed to erosion–corrosion (EC) processes that significantly reduce their service lifetime. Difficulties predicting material loss in industrial machinery, financial and security impacts due to early failure of worn components and the necessity of managing highly aggressive slurries (e.g. oilsands), have motivated the application of surface engineering solutions to reduce the negative effects of erosion–corrosion processes. The erosion–corrosion resistance of nickel base and iron base metal matrix composites (CNi and CFe MMCs, respectively) coatings was studied in this paper. The behavior of the MMCs compared with their non-reinforced matrices (NRMs); tungsten carbides (WC) particles were used to reinforce the NRMs. The microstructures of the NRMs and MMCs were analyzed by microscopy techniques and the effects of adding a reinforcing phase to the matrices are reported and linked to their EC resistance. The EC resistance was assessed at different sand contents (10 and 50 g/l) and temperatures (20 and 65 °C) using a submerged impinging jet (SIJ) apparatus; the MMCs were also studied under EC at 5, 10 and 14 m/s to analyze the structural integrity of the reinforcing phase. The results shown that, the CNi was the more EC resistant coating under most of the experimental conditions, at 5 m/s the EC degradation mechanism was dominated by matrix degradation with the WC showing little damage and the CFe was negatively affected by corrosion, especially at 65 °C. Interestingly, the MMCs were more susceptible to changes in temperature whereas, for the NRMs EC resistance was more affected by the sand content of the slurry.