Aspects of microstructure on the synergy and overall material loss of thermal spray coatings in erosion–corrosion environments

The influence of microstructure on the overall material loss in erosion–corrosion environments is presented for WC–Co–Cr coatings applied by (i) High Velocity Oxy-Fuel (HVOF) and (ii) Super Detonation-Gun (D-Gun) processes. The study is focused on understanding the synergy effect (here defined as the enhancement of erosion due to corrosion effects) on material loss when two different microstructures are formed and also the influence of chemical composition of the coating. Experiments showed that HVOF coatings have a slightly lower corrosion resistance than the Super Detonation-Gun (D-Gun) coatings but higher overall erosion–corrosion resistance. It is important to point out that HVOF and Super D-Gun coating microstructures vary depending on parameters of application and therefore the results presented in this paper cannot be generalised. In this work a particular case is presented to establish a link between the coating composition, microstructure and erosion–corrosion performance for WC–Co–Cr coatings when different microstructures are formed.