Tribological Behaviors of CrN and CrAlN Coatings in Seawater

The CrN and CrAlN coatings were deposited on 316L stainless steel substrate by multi-arc ion plating. The composition and structures of coatings were characterized by X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy. The hardness and adhesion of the coatings were measured by using nanoindentation and scratch tester, respectively. The friction and wear properties of coatings were investigated by a ball-on-disk tribometer in seawater. The results show that the two coatings had comparble friction coefficient in seawater . The friction coefficient of 316L was higher than that of the two coatings and fluctuated severely, indicating the tribological property of 316L in artificial seawater. The wear rates of the two coatings in seawater were much lower than that of 316L, and the CrAlN coating had better wear resistance than CrN coating in artificial seawater. There were a lot of wear pits on the wear track of CrN coating due to the delamination of macroparticles. However, despite the low hardness, the CrAlN coating had low wear rate, which can be attributed to the denser structure, good corrosion resistance and tribo-chemical product Al₂O₃. The mechanical properties, the structure, anti-corrosion properties and anti-wear properties should be taken into consideration for the coatings used in seawater.