Multiscaled analysis of wear mechanism of titanium and carbon basis multilayer coatings

Purpose: The wear mechanisms of Ti/TiN and (TiN/Ti/a-C:H) multilayer coatings were investigated. Coatings were deposited using the hybrid Pulsed Laser Deposition technique (PLD) on austenitic stainless steel. The microstructure investigations were performed with the TECNAI G2 SuperTWIN FEG (200kV) transmission electron microscope. Ceramic TiN and a-C:H layers showed brittle cracking, while very thin metallic Ti layers were deformed plastically. The presence of metallic phase led to the cracking resistance and increased an energetic cost of propagating cracks. Design/methodology/approach: Ti/TiN and (TiN/Ti/a-C:H) multilayer coatings were deposited on austenitic stainless steel (316L) using the hybrid PLD (Pulsed Laser Deposition + magnetron sputtering) equipped with high purity titanium target (99.9% at. Ti) and carbon target. Microstructure was analyzed on thin foils prepared using the FEI Dual BeamTM FIB system equipped with an Omniprobe lift-out technique. Foils were cut perpendicularly both to coating surface and wear path. The microstructure observations were performed using TECNAI F20 SuperTWIN (200kV) transmission electron microscope. Findings: The wear mechanism of the multilayer coating was realized through brittle cracking of ceramic layers and plastic deformation of metallic ones. Research limitations/implications: Optimization of layer thickness and modulation; application of advanced deposition and diagnostic methods. Practical implications: Switching from mono- to multi-layered coatings allows changing the mechanism of wear from through-coating cracking leading to catastrophic delamination to more gradual layer-by-layer coating removal. The farther wear decrease should be sought at lower multilayer period. Originality/value: Design and fabrication of Ti/TiN and (TiN/Ti/a-C:H) multilayer coatings revealing an improved behavior in service systems subjected to wearing. Multiscale microstructure diagnostics of multilayer coatings.