Comparison of properties of ZrHf-(Zr,Hf)N-(Zr,Hf,Cr,Mo,Al)N and Ti-TiN-(Ti,Cr,Al)N nanostructured multilayer coatings and cutting properties of tools with these coatings during turning of nickel alloy

The paper compares the properties of two nanostructured multilayer coatings of Ti-TiN-(Ti,Cr,Al)N and Zr,Hf-(Zr,Hf)N-(Zr,Hf,Cr,Mo,Al)N. The Ti-TiN-(Ti,Cr,Al)N coating has higher hardness, but is prone to increased adhesion in a tribological pair. The results of cutting tests during the turning of Inconel 718 nickel alloy find that a tool with the Zr,Hf-(Zr,Hf)N-(Zr,Hf,Cr,Mo,Al)N coating has a significantly longer tool life. The study focused on wear patterns of the tools with the coatings under comparison revealed significant differences between them. For tools coated with Ti-TiN-(Ti,Cr,Al)N, the formation of an extensive adherent of the material being machined is typical, with adhesive-fatigue processes dominating in wear. For tools coated with Zr,Hf-(Zr,Hf)N-(Zr,Hf,Cr,Mo, Al)N, the key role in wear is played by the oxidation processes associated with the active formation of a mixture of (Zr,Hf)O2 oxides. The formation of clusters with a dendritic structure is observed under the influence of embedded microparticles. The nanolayer boundaries can perform a barrier function against oxygen diffusion and, accordingly, restrain further oxidation of the coating.