Microstructure, mechanical and tribological properties of gradient CrAlSiN coatings deposited by magnetron sputtering and arc ion plating technology

• Three CrAlSiN coatings with gradient contents are prepared by a hybrid process. • The hardness increases with linear ultimate power. • Inversely, adhesion strength and wear resistance decrease gradually. • Abrasive wear is the main cause for the failure of the former two coatings. • Exfoliation leads to highest wear rate of coating with largest linear ultimate power. Three CrAlSiN coatings with gradient concentrations of Al and Si ascending from the transitional layer to the surface were prepared by a combined method of direct current magnetron sputtering and arc ion plating using linearly increasing sputtering power. Microstructure, mechanical and tribological properties of the three gradient coatings were studied. Results show that all coatings possess face-centered cubic CrN phase with small amounts of hexagonal close packed AlN phase. The preferential orientation of the gradient coatings evolves from (111) to (220) crystal plane as the linear ultimate power is enlarged from 1.2 kW to 2.8 kW. The hardness increases gradually with the linear ultimate power, while the adhesion strength and wear resistance of the three coatings decrease gradually. For all the three gradient coatings, slight oxidation occurs at the boundaries of the wear track. Abrasive wear is the main failure mode for the CrAlSiN coating with linear ultimate power of 1.2 kW and 2.0 kW, while exfoliation resulting from low crack resistance is the primary cause for the highest wear rate of the CrAlSiN coating with linear ultimate power of 2.8 kW.