Influence of Treatment Sequence on Tribological Performance of Duplex Surface-Treated AISI 1045 Steel

The surface of AISI 1045 steel specimens was modified via two duplex surface treatments of (i) titanium diffusion coating followed by plasma nitriding (Ti-PN) and (ii) plasma nitriding followed by titanium diffusion coating (PN-Ti). A comparative study on the microstructure and wear properties of the fabricated TiN coatings was conducted. A scanning electron microscope equipped with energy-dispersive X-ray spectroscopy, X-ray diffractometer (XRD), and pin-on-disk wear test was utilized to evaluate the microstructures, phases, and wear properties of the coatings. XRD patterns of duplex-treated specimens illustrated that the modified layer consisted of nitride and carbo-nitride phases such as TiN and TiC_0.7N_0.3. The results also showed that Ti-PN treatment led to a low friction coefficient and the lowest wear factors, as compared with the PN-Ti treatment. Oxidation and mild fatigue fracture wear were found to be the main wear mechanism of the Ti-PN coating. The wear mechanism in the PN-Ti specimen involved a higher oxidative wear regime followed by plastic deformation wear regimes.