Tribological properties in seawater for Ti/TiCN coatings on Ti6Al4V alloy by arc ion plating with different carbon contents

Abstract

TiCN coatings incorporated with Ti buffer layer were deposited on Ti6Al4V alloy by arc ion plating. The carbon content in TiCN coatings was varied by controlling flow rates of C2H2 in reactive gas. The Ti/TiCN coatings have a typical structure of columnar crystal with a total thickness of about 2 µm. The elements of Ti, C and N are present as TiN and TiC in TiCN coatings. A little free carbon appears with carbon content increasing in TiCN coatings. For the TiCN coatings, the hardness, friction coefficient and wear rate decrease with the increase in carbon content. In seawater, both friction coefficient and wear rate have an obvious decrease at lower carbon content compared with those in atmosphere. However, the friction coefficient and wear rate only have a slight decrease, while the carbon content reaches or exceeds 10 at% in Ti/TiCN coatings.