Improved nanomechanical test techniques for surface engineered materials

Abstract

The development and implementation of a wide range of innovative nanomechanical test techniques to solve tribological problems in surface engineered systems are described in this review. By combining results with several different nanomechanical techniques, predictive design rules based on the elastic and plastic deformation energies involved in contact are proposed to optimise mechanical properties in the various contact situations that occur for different applications. Results are presented with the NanoTest platform for applications in biomedical devices, surface engineering of lightweight alloys, wear resistance of physical vapour deposition and chemical vapour deposition coatings as well as fracture fatigue resistance of diamond-like carbon coatings. Surface engineering to increase the ratio of hardness to elastic modulus (H/E) can be beneficial in a range of applications but care should be taken that, first, it be done without introducing too large intrinsic stress or stress discontinuities in mechanical contact loading, second, the severity of the contact results in high stresses and there is a requirement for some plasticity in contact to avoid fracture.