TiN/NbN Nanoscale Multilayer Coatings Deposited by High Power Impulse Magnetron Sputtering to Protect Medical-Grade CoCrMo Alloys

This study describes the performance of nanoscale multilayer TiN/NbN coatings deposited on CoCrMo medical-grade alloys by utilising novel mixed high power impulse magnetron sputtering (HIPIMS) and direct current unbalanced (UBM) technique in an industrial size vacuum coater. Scanning electron microscopy analysis showed that these were extremely dense without any intercolumnar voids. The coating exhibited hardness 28 GPa, as well low friction wear coefficient 0.7 1.4 × 10−14 m3·N−1·m−1, respectively, compared to bare material. Scratch tests revealed superior substrate adhesion due HIPIMS etching prior deposition. Energy-dispersive X-ray debris generated during impact test together with focused ion beam cross-section different locations crater failure mechanism further confirmed excellent bonding strength. Potentiodynamic polarisation NaCl Hank’s solutions clear passivation behaviour, several orders magnitude lower corrosion currents, pitting potentials coating, which guarantee protection base alloy such aggressive environments. Inductively coupled plasma mass spectrometry solution containing coated sample leaching harmful metal ions from material was reduced below detection limit technique, thus demonstrating barrier properties coating.