Deformation of Ultra-Thin Diamond-Like Carbon Coatings Under Combined Loading on a Magnetic Recording Head

Ultra-thin diamond-like carbon (DLC) coatings are used in precision engineering applications, such as magnetic storage devices, to protect intricate structures from wear and corrosion. A DLC coating typically consists of hard amorphous carbon in combination with an interlayer such as silicon (Si), to improve adhesion to the substrate material. Deformation and delamination of these coatings, even in part, could expose the substrate material and compromise its integrity and functionality. We have implemented a molecular dynamics model to quantify the strength of the interface between an ultra-thin tetrahedral amorphous carbon coating, a Si layer, and a permalloy (NiFe) substrate, under combined normal and tangential loading that mimics accidental contact between the recording head and the disk of a hard drive. We have evaluated the effect of the thickness of the different coating layers on deformation and interfacial strength of the coating during combined loading. The results indicate that deformation occurs primarily in the Si layer, and at the interface between the Ni–Si and the Si–C layers. Permanent separation of the Si and ta-C layers is observed, which gradually increases with multiple combined loading cycles. We find that increasing the Si and carbon layer thickness strengthens the DLC coating. However, increasing the carbon layer thickness has a larger effect on coating strength than increasing the Si layer thickness.