Delamination and Longitudinal Cracking in Multilayered Composite Nanostructured Coatings and Their Influence on Cutting Tool Wear Mechanism and Tool Life

Abstract

The wear and failure mechanism for multilayered nanostructured coatings has a number of significant differences from the one typical for monolithic single-layered coatings. In particular, while the strength of adhesion bonds at the "substrate-coating" boundary is important for monolithic coatings, then for multilayered nanostructured coatings, the strength of adhesion and cohesion bonds at interlayer boundaries and boundaries of separate nano-sublayers becomes of significant significance. Meanwhile, the delamination arising in the structure of multilayered nanostructured coatings can have both negative (leading to loss of coating uniformity and subsequent failure of coating) and positive influences (due to decrease of internal stresses and inhibition of transverse cracking). Various mechanisms of formation of longitudinal cracks and delaminations in coatings on rake tool faces, which vary based on the compositions and architectures of the coatings, are studied. In addition, the influence of internal defects, including embedded microdrops and pores, on the formation of cracks and delaminations and the failure of coatings is discussed. The importance of ensuring a balance of the basic properties of coatings to achieve high wear resistance and maximum tool life of coated metal-cutting tools is shown. The properties of coatings and the natures of their failures, as investigated during scratch testing and dry turning of steel C45, are provided.

Influence of aluminium and molybdenum on properties of coatings and cutting properties of coated tools

“…The Cr,Mo-(Cr,Mo)N-(Cr,Mo,Al)N multilayered composite coating with a nanostructured wear-resistant layer was deposited through the VIT-2 unit [29][30][31][32][33][34][35][36][37][38] using the filtered cathodic vacuum arc deposition (FCVAD) technology [33][34][35][36][37][38] to minimize the number of microdroplets and secure the formation of a nanolayer structure with the nanolayer thickness of 0.5 nm and greater. A three-layer architecture of the coating was applied, including an adhesion layer of Cr,Mo, a transition layer of (Cr,Mo)N, and a wear-resistant layer of (Cr,Mo,Al)N [26].…”

Influence of the nanolayer structure of coatings on the cutting properties of tools

“…The Ti-TiN-(Ti,Al,Cr)N multilayered nanostructured coating with a varying thickness of nanolayers in a (Ti,Al,Cr)N wear-resistant layer was deposited using the VIT-2 unit [32][33][34][35][36], on which the filtered cathodic vacuum arc deposition (FCVAD) technology was implemented [37][38][39][40][41][42]. Depending on the turntable rotation frequency (from 0.25 to 7.0 rev/min), the nanolayer thickness varied during the deposition of the coatings.…”