Mechanism of TiC formation in laser surface treatment of the commercial pure titanium pre-coated by carbon using PVD process

The physical evaporation deposition (PVD) and titanium (CPeTi) plate. The influence of area scanning speed on the structure of coating were studied by changing the laser working distances and Nd:YAG laser traveling speeds. Scanning electron microscopy (SEM) and also field emission scanning electron microscopy (FE-SEM) equipped with energy dispersive spectroscopy (EDS) were utilized to investigate the samples. The structure of produced coating mainly was affected by area scanning speed. At area scanning speeds lower than 7.5 mm(2)/s, one layer low TiC composite was produced due to the formation of deep melt pool with long melting time. One layer high TiC composite formed at area scanning speeds higher than 20 mm(2)/s as a result of shallow melt pool. Between theses values, two layers coating consisting of high and low TiC composite was obtained because the melt pool was relatively large and the required melting time for homogenization was not provided. The micro-hardness measurements showed that, the highest hardness (up to 6 times higher than the substrate) was obtained when two layers coating were synthesized. The dry sliding wear test demonstrated 62-93% reduction in the mass losses and wear rates in the two layers coatings. The average friction coefficient of the two layers coating reduced about 77%. (c) 2020 Elsevier B.V. All rights reserved.