Residual stress control in CrAlN coatings deposited on Ti alloys

In order to control residual stress of CrAlN coatings on Ti substrates, ~70 nm CrAl interlayer was deposited at different temperatures. Residual stress and coatings' structure were characterized by X-ray diffraction. Residual stress in the coatings was compressive and increased with CrAl interlayer deposition temperature. Residual stress in 1.5 µm, 2 µm and 2.6 µm thick CrAlN films on TC21 with the interlayer deposited at 100 °C (−47.43 MPa, −25.57 MPa and −855.77 MPa, respectively) was smaller than with the interlayer deposited at 300 °C (−1.39 GPa, −1.95 GPa and −1.62 GPa, respectively). The coatings on the TC4 substrate showed the same trend (−1.02 GPa, −389.91 MPa and −1.03 GPa for the interlayer deposited at 100 °C, respectively, and −921.42 MPa, −2.31 GPa and −1.80 GPa for the interlayer deposited at 100 °C, respectively). Changing the interlayer deposition temperature can influence the coatings' residual stress and crystal structure, and improve mechanical properties of the coatings. CrAlN deposition is a convenient and efficient way to improve mechanical properties of Ti alloys.