Wear Resistance, Patterns of Wear and Plastic Properties of Cr,Mo-(Cr,Mo,)N-(Cr,Mo,Al)N Composite Coating with a Nanolayer Structure

Abstract

This paper discusses the results of studies focused on the wear resistance, patterns of wear and plastic properties of Cr,Mo-(Cr,Mo,)N-(Cr,Mo,Al)N coating, containing 20 at.% Mo. The coating had a nanolayer structure with a modulation period λ = 50 nm. The studies revealed the hardness, fracture resistance in scratch testing, as well as elemental and phase composition of the coating. The studies of the tool life of carbide cutting tools with the Cr,Mo-(Cr,Mo,)N-(Cr,Mo,Al)N coating proved their longer tool life compared to that of uncoated tools and tools with the reference Cr-(Cr,Al)N coating of equal thickness and equal content of aluminum (Al). The studies included the comparison of the tools coated with Cr,Mo-(Cr,Mo,)N-(Cr,Mo,Al)N and Cr-(Cr,Al)N. The experiments focused on the specific features of the coating nanostructure and were conducted using a transmission electron microscope (TEM), revealing the different mechanisms of fracture. The penetration of particles of the material being machined between nanolayers of the coating results in interlayer delamination. When exposed to a moving flow of the material being machined, plastic deformation (bending) of the coating nanolayers occurs. The diffusion of iron into the coating (up to 200 nm) and diffusion of Cr and Mo into the cut material to a depth of up to 250 nm are observed. The presented information can help in the design of metal cutting tools and the choice of coatings for them.