Nanolayer (Ti,Cr)N coatings for hard particle erosion resistance

This paper discusses the synthesis and characterization of titanium chromium nitride ((Ti,Cr)N) thin films deposited onto AM355 stainless steel by multi-source cathodic arc physical vapor deposition (PVD) for improved erosion resistance. The effect of Cr evaporator current and substrate bias on the erosion resistance of the (Ti,Cr)N coating were investigated. The coatings were characterized using X-ray diffraction, scanning electron microscopy, electron probe microanalysis, scanning transmission electron microscopy, scratch adhesion testing and erosion testing. The (Ti,Cr)N coatings deposited using multisource mode were determined to be nanolayered structures consisting of TiN rich and CrN rich layers. EPMA showed that the atomic percentage of Cr within the coating increased (increased Cr:Ti ratio) with increasing Cr evaporator current and that the (Ti,Cr)N chemical composition did not appear to change with varying bias. Using XRD and STEM, it was determined that all nanolayer (Ti,Cr)N coatings were multi-phased consisting of a B1 NaCl crystal structure. XRD also revealed that as the Cr evaporator current was increased, there was an increase in the CrN phase volume. Macroparticle incorporation increased with an increase in Cr evaporator current and decreased with an increase in bias. The nanolayer (Ti,Cr)N coatings ranged in Vickers hardness from 1700 to 2800 VHN0.050. Coating adhesion increased as Cr:Ti ratio increased. In regards to erosion, (Ti,Cr)N coatings with a high number of TiN/CrN interfaces performed poorly against alumina media. As the Cr evaporator current was varied, the coating deposited with the highest Cr:Ti ratio (evaporator current of 85 A) and when bias was varied, the lowest substrate bias of - 50 V had the best erosion performance.