Impact of the Stand-Off Distance and Spray Angle on the Corrosion, Cavitation and Erosion Behaviour of the Thermal Spray Layers Deposited by the Three-Cathode Spraying

Abstract

Fe-based coatings, such as novel FeCrMnBC alloys, have both economic and ecological advantages compared to other coatings like Ni-based or Co-based coatings. In recent years, high performance Fe-based wear and corrosion resistant coating systems have been developed. Some of them have even been introduced into the market. However, the suitability of the FeCrMnBC alloy as coating for cast iron under complex erosive and corrosive stresses in particle-loaded fluids for pump parts has not been investigated yet. Especially the impact of the process robustness of three-cathode plasma spraying coatings applied with variable process parameters like stand-off distance and spray angle is in the focus of interest. The objective of the present work has been the characterization of novel FeCrMnBC alloys, for the first time deposited via Thermal Spray processes. The corrosion resistances as well as the cavitation and erosion properties were separately evaluated by current density-potential measurements and supersonic cavitation in artificial sea water. Erosion corrosion behavior has been investigated in a pump test rig with 10 wt.-% corundum (Al2O3) particles. The results show that the reduction of spray angle and the variation of stand-off distance limit the corrosion and cavitation resistance in different ways. The erosion behavior shows only small variations for the tested parameters. The results reveal that the FeCrMnBC coatings exhibit high process robustness for the chosen parameter variations and a large potential to improve the protection of cast iron even for not optimized conditions.