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In this work, the competitive relationship between the double amorphous phases is systematically investigated to increase the high-temperature wear resistance of the self-lubricating TiAlSiCN coating. These double amorphous phases combine the SiN x phase with high-temperature resistance and the C-related phase with a low friction coefficient. An increase in the Si content facilitates the change in the phase composition. The resultant coating exhibits an adhesion strength of 153 N, a friction coefficient of 0.24 and a hardness of 25.24 GPa upon generation of the TiAlN(C), the SiN x and the C-related phase. In this case, the TiAlSiCN coating achieves long-term self-lubrication at high temperatures with the titanium alloy friction pair. This mechanism stems from the SiN x phase replacing the portion of the easily oxidized amorphous C-related phase, which yields an enhanced high-temperature wear resistance. The cutting distance of this TiAlSiCN is 120% higher than that of the TiAlCN during the high-speed cutting of the titanium alloy. This outcome provides an effective solution for high-temperature applications of self-lubricating coatings. • Long-term self-lubricating is remained in TiAlSiCN coating by optimal Si content. • Synergistic effect of amorphous SiN x and C-related phase is solved in TiAlSiCN. • Tool life of TiAlSiCN improved 225% by comparing with that of TiAlN. [ABSTRACT FROM AUTHOR]

In order to satisfy the requirements of tool coatings for high speed cutting of titanium alloy, it is necessary to add Si element into TiAlN-based tool coating to enhance the hardness of the coating, but it will reduce the adhesion and the cutting performance. In this paper, the gradient TiAlSiN coating is deposited with out-of-plane Si gradient distribution by magnetron sputtering. By this way, the hardness of the coating can maintain that of the non-gradient TiAlSiN coating by more than 70%, which is 147% higher than that of the TiAlN coating. Meanwhile, the adhesion increases by 300% compared to the adhesion of the non-gradient TiAlSiN coating and reaches to 100 N. The gradient TiAlSiN coating has a 75.4% higher cutting distance than that of the non-gradient TiAlSiN coating when cutting titanium alloy. This study provides a method to further improve the adhesion of titanium alloy cutting tool coatings. • Gradient structure improves adhesion of coating while maintaining hardness. • Adhesion of gradient TiAlSiN coating increases by 300% than that without gradient. • Cutting distance increases by 75.4% due to Si gradient in TiAlSiN coating. [ABSTRACT FROM AUTHOR]