Industrial-Scale Production of Corrosion-Resistant CrN/NbN Coatings Deposited by the Combined High Power Impulse Magnetron Sputtering Etching Unbalanced Magnetron Sputtering Deposition (HIPIMS/UBM) Process

摘要

We report on the utilization of a novel technology - high power impulse magnetron sputtering (HIPIMS) for the engineering of droplet-free interfaces that promote adhesion of hard corrosion-resistant coatings. An industrial scale commercial deposition system was used to pretreat the substrates by HIPIMS and sputter-deposit a CrN/NbN nanoscale multilayer coating (bi-layer thickness = 3.5 nm). Successful upscaling of the HIPIMS discharge from laboratory to production scale (> 1200 cm~2) cathodes was evidenced by similarities in I-U characteristics, substrate current densities (Js) and plasma composition. The peak discharge current densities reached 2 Acm~(-2) at a duty cycle of 1% and the Js reached 300 mAcm~(-2) peak. HIPIMS operated on large cathodes produced strong optical emission signals from singly ionized metal species for Nb targets. The adhesion of the CrN/NbN coatings was excellent with scratch test critical loads of 56 N exceeding the values of 43 N achieved for arc etching for identical coatings. The performance of the coating in potentiodynamic corrosion tests showed extremely low passivation currents in the range of 10~(-5) Acm~(-2) for carbon steel substrates. PVD coated 304 stainless steel spools matched the performance of electroplated hard Cr coated spools in salt spray tests.