Tensile direction dependent failure of laser pretextured TiN coating/stainless steel substrate

Abstract

Laser pretexturing is widely used as an efficient way of modification to enhance the interfacial properties between coating-substrate pairs. The effect of the relative orientation between the laser texture and the loading direction on the mechanical properties of coating and interface is not yet known. To this end, the present work aims at investigating the effect of tensile direction on the failure of laser pretextured TiN coating/stainless steel substrate. Transverse and longitudinal textures were separately etched on the 304 stainless steel substrate using pulsed laser technology, followed by depositing TiN coating via magnetron sputtering technique. X-ray diffraction (XRD) and nanoindentation tests were conducted to measure the residual stress, elastic modulus and hardness of both substrate and coating. The stages of coating failure were examined through in-situ tensile experiments and comparative assessment was made on the properties such as interfacial shear strength (ISS) and critical energy release rate (CERR). Results showed that the CERR and ISS decreased by 21 % and 8 % respectively for the transversely pretextured (TP) specimen. In contrast, the ISS was increased by 36 % for the longitudinally pretextured (LP) specimen, for which the compressive residual stress on the surface of the substrate was transformed into tensile stress by laser pretexturing, and the texture morphology acted as a stress reliefer, alleviating the buckling and shear damage of coating. These findings are expected to offer insights into understanding the failure mechanism of laser pretextured TiN coating/304 stainless steel substrate and to provide a helpful reference for the effecient design of relevant laser textures.