Effects of air plasma spraying parameters on the Al–Cu–Fe quasicrystalline coating layer

The focus of this study has been the effect of air plasma spray processing parameters on the characteristics of the Al–Cu–Fe quasicrystalline coatings. Key variables controlling the particle temperature and velocity and substrate temperature, such as the arc current, spraying distance, powder flow rate, and preheating of the substrate surface, were of primary interest. Significant effects of the process parameters on the microstructure and subsequent mechanical properties of the coatings were observed. Process conditions favorable for the formation of coating layers with larger amount of quasicrystalline phase led to the higher values of the microhardness, although it resulted in a relatively large porosity level. The bonding strength was found to be slightly dependent on the spraying distance, powder feeding rate, and preheating of the substrate. However, the predominant variable appeared to be the coating thickness, where a significant reduction of the bonding strength was reported as the coating thickness was increased up to 100 μm.