Using a pure metal interlayer to relieve residual stress and enhance adhesion of hard coatings on substrate materials has been commonly adopted in industry and extensively studied in last two decades. However, due to the difficulty in accurately measuring residual stress in individual layer of a bilayer coating, the effect of stress relief by a pure metal interlayer has not been fully understood. Recently we proposed a method combining average X-ray strain (AXS) method and nanoindentation (NI), by which the residual stress of hard coatings can be accurately measured with an uncertainty
