In this study, the surface of a piston (AlSi12CuNi) belonging to a diesel engine was coated with ZrO2+MgO/Al2O3 powders by using plasma spray technique. The coating layers were examined with optical microscopy, SEM, EDS and XRD analysis. The adhesive strength and microhardness were measured. In XRD studies, such compounds as ZrO2 (Tetragonal), ZrO2 (Monoclinic), MgO, Al3Zr5, alpha-Al2O and gamma-Al2O3 have been identified on ZrO2+MgO/Al2O3 coating layers. The best adhesion strength and maximum hardness value have been determined in the sample coated with ZrO2+MgO+ 50wt. %Al2O3 powder.