Effect of CrAl interlayer on adhesion strength of CrAlN coating

CrAlN coating is widely used to prevent Ti alloy from wear nowadays, however, the poor adhesion between the coating and substrate is an urgent problem to resolve. In this paper, CrAlN coating with CrAl intermediate layer is prepared on Ti alloy by RF magnetron sputtering technique. The adhesion strength of the coating is measured by automatic scratch tester. The results show that the adhesion strength of CrAl/CrAlN coating is much higher than that of mono-layer CrAlN coating. The CrAl layer with thickness of 5.07??m displays an excellent adhesion strength, which is 84.2?N. The nano-hardness and elastic modulus are 26.45 and 215.33?GPa, respectively. The improvement of adhesion strength can be attributed to the two reasons: (1) the elastic modulus of the CrAl layer is between the Ti alloy and the CrAlN coating, playing a role of stress transition. (2) The intermediate layer inhibits the columnar growth of CrAlN.