Ref.: MceFsu17-002

Insights into the impact of multilayer engineering on the microstructure and micromechanical behavior of hard ceramic coatings

Apresentador: Haroldo Cavalcanti Pinto

Autores (Instituição): Apolinário, R.(Universidade de São Paulo); Rodrigues, A.(Universidade de Brasília); Avila, P.(Universidade de São Paulo); Pereira, J.(Universidade de São Paulo); Azhari, I.(Saarland University); Schäfer, F.(Saarland University); Ramirez, C.(Centro Nacional de Pesquisa em Energia e Materiais); Moreto, J.A.(Universidade de São Paulo); Greiner, C.(Karlsruhe Institute of Technology); Pinto, H.C.(Escola de Engenharia de São Carlos da Universidade de São Paulo);

Resumo:
The effect of superimposing a nano modulation of sublayers with the multilayer architecture on the micromechanical behavior of hard multilayer systems has been investigated. To this end, Dynamic Glancing Angle Deposition (DGLAD) using variable amplitudes of pendular substrate displacement has been applied to (Cr,Y)N/(Cr,Y)2N multilayers grown by High-Power Impulse Magnetron Sputtering (HiPIMS) to tailor the nano modulation into the individual sublayers. DGLAD generated fine nanostructures characterized by zig-zag grain growth and corrugated grain boundaries, whereas HiPIMS using a standing substrate produced the typical columnar grain morphology. Significant hardness improvement from ~25 up to ~33 GPa was achieved for DGLAD with intermediate substrate oscillation. Comparable compressive residual stresses were verified for both, (Cr,Y)N and (Cr,Y)2N nitrides, and DGLAD largely influenced their magnitude, demonstrating its potential to tailor residual stresses in hard coatings. Compression tests of micro-pillars have demonstrated that these hard multilayered coatings are tough and can reach an ultimate strength of around 10 GPa with a maximum strain of 5%. Yield and ultimate strength, as well as elongation to failure were higher for the columnar microstructure, whereas more elevated hardness and resistance to plastic indentation (H3/Er2) were verified for the nanostructure with zig-zag grain growth and corrugated grain boundaries. This divergence suggests, however, that DGLAD causes a slightly reduced interfacial/boundary cohesion, which favors grain boundary sliding and an earlier failure when the deformation is applied under conditions of low constraint and samples with elevated surface-to-volume ratio. To the best knowledge of the authors, it is highlighted for the first time that hard ceramic multilayers may exhibit plastic strain to failure, which is governed by slipping and shear bands.