NiCrAlY-PSZ graded materials with two different gradients were synthesized using the plasma spray technique. Their microstructure, thermal and frictional response were evaluated, and the response was compared to that of single layered composite materials. The hardness and frictional properties of PSZ could be successfully optimized by an addition of small amount of NiCrAlY. The results of testing revealed the potential of ceramic/metallic materials systems and can be used to further optimize the spraying process of composite/graded structures subjected to contact damage at high temperatures. The study also revealed new tribo-effects that can be encountered in potential applications of graded structures.

Al-Cu-Fe quasicrystalline coatings, due to their high hardness and low friction coefficients, are potential candidates for improving the wear resistance of ductile materials. However, technological applications may be limited on account of their brittle nature. This study examines the effects of starting powder composition and thermal spray process parameters on the phase assemblage, microstructure, and tribological response of Al-Cu-Fe thermally sprayed coatings. It was found that the coatings fail by a delamination mechanism in unlubricated unidirectional sliding wear. Furthermore, the coatings produced by the high velocity oxy-fuel technique showed a very low coefficient of friction and wear rate.