Cr-containing diamond-like carbon coatings deposited on 316 stainless steel substrates: Characterization and interfacial fracture toughness measurements

A series of Cr-containing hydrogenated amorphous carbon (a-C:H:Cr) coatings were deposited onto 316 stainless steel (316SS) substrates using inductively coupled plasma assisted reactive sputter deposition. Elemental Cr interlayers with different thicknesses of 100, 200, and 300 nm were deposited between a-C:H:Cr and 316SS. Detailed composition, structure, and mechanical behavior characterization of deposited a-C:H:Cr/Cr/316SS specimens were performed. Fracture toughness values of the a-C:H:Cr layer, the Cr layer, and the a-C:H:Cr/Cr/ 316SS interfacial regions were measured by bending of microcantilever beams with focused ion beam milled pre-notches in-situ a scanning electron microscope. Measured fracture toughness of a-C:H:Cr/Cr/316SS interfacial regions exhibits an approximately linear correlation with the area fraction of the fracture surface occurring in the Cr interlayer, indicating that the interfacial fracture toughness depends on the detailed path of crack propagation and suggesting that interfacial toughness can be engineered through materials design of the interfacial region.