Variation of Heat Input and Its Influence on Residual Stresses and Coating Properties in Arc Spraying with Different Gas Mixtures

Abstract

This work is about the influence of heat input on arc-sprayed coatings, caused by varying spraying patterns. The highly cavitation erosion-resistant alloys CuAl9Ni5Fe4Mn and CuMn13Al8Fe3Ni2 were arc-sprayed with a spiral-shaped pattern, using both pressurized air and a mixture of nitrogen and hydrogen. Process temperatures were recorded by thermographic imaging, and residual stresses were measured by modified hole-drilling method. Moreover, analyses of the cavitation erosion behavior and other properties were performed. Compared to previous own works, in which a meander-shaped spray pattern was used, most importantly the thermal loads, for example the maximum temperatures, during the coating buildup were lowered up to approx. 20 °C. Moreover, a more even heating of the specimens and reduced tensile stresses for both atomizing gases and materials were achieved. Furthermore, also the course of the residual stresses was changed. Hence, the dominance of the quenching stresses regarding residual stresses and coating properties, especially when spraying with pressurized air, was found to be reduced. In addition, the cavitation erosion resistance was improved severely, i.e., erosion depth was decreased up to 57%. In contrast to the aforementioned positive effects, the deposition efficiency, Young’s moduli and hardness were reduced, but still sufficient considering the application.