The Costly Mistake of Applying Hard Coatings to an Unhardened Surface
Applying hard coatings onto an unhardened surface of a lightweight metal leads to the potential of cracks and delamination caused by inadequate support of the coating. This inadequate support is caused by the large difference in hardness between the surface and the hard coating [1,2]. This is also known as the "eggshell" effect.
Finite element modeling analysis has shown that in most coating systems, plastic deformation initiates at the interface under high normal loads and plastic deformation does not occur in the coating until a substantial, plastically-deformed region has developed in the substrate, underneath the coating .
Surface engineering is not about simply selecting existing treatments to alleviate problems from poor material selection or poor material performance. The focus of surface engineering is to design a surface that can provide a cost-effective solution that can produce the desired surface properties . One possibility of solving these obstacles that must be overcome is the use of duplex surface treatments. A properly selected duplex surface treatment will enable the material to withstand high contact loads and resist scuffing and wear. Creating a duplex surface treatment by nitriding titanium and then applying a Diamond-Like Carbon (DLC) coating has shown favorable results .