Mechanical and structural properties of multilayer c-BN coatings on cemented carbide cutting tools

Multilayer cubic boron nitride (c-BN) coatings represent a new deposition method that can improve adhesion on metal substrates. The multilayer c-BN system in this study consisted of a TiAlN interlayer (2- 3.5 mm), boron carbide (~ 1 mm), and a c-BN (~ 2 mm) gradient layer. This multilayer c-BN structure, exceeding 5 mm in thickness, showed outstanding adhesion in atmospheric conditions even with high residual stress. Compared to monolayer c-BN coatings, the multilayer c-BN films had lower elastic moduli, and their critical loads were twice as high. The adhesion of the multilayer c-BN system was significantly improved because of the induced stress relaxation.