Microstructure effects on fracture failure mechanism of CrAl/CrAlN coating

In this work, the Metal-rich phase Chromium Aluminum (CrAl)/Ceramic phase Chromium Aluminum Nitride (CrAlN) multi-layer coatings were prepared by Arc Ion Plating (AIP). The micro-structure and phase composition of CrAl/CrAlN multi-layer coatings were characterized, and the microstructure, mechanical properties, residual stress and fracture toughness of the coating were emphatically analyzed. It has been found out that the residual stress of the multi-layer coating was only-0.932 +/- 0.065 GPa, which was significantly lower than that of the mono-layer coating for-1.569 +/- 0.093 GPa. At the same time, it was also found that the preferred growth orientation of the coating changed from a mono-layer (111) to a multi-layer (200) crystal plane. The hardness of the multi-layer (22.74 +/- 0.57 GPa) is slightly lower than that of the mono-layer (24.92 +/- 0.5 GPa), and the adhesion strength (46.2 +/- 3.8 N) is obviously higher than that of the mono-layer (37.4 +/- 2.4 N), and the fracture toughness is also higher (8.7 +/- 0.8 MPa m1/2). In addition, the mechanism of crack initiation and propagation in stress-induced coatings was studied in detail on the basis of the structure of micro-nano CrAl/CrAlN multi-layer coatings.