Influence of mechanical properties of coating and substrate on wear performance of HDLC and TiN-coated AISI 5140 alloy steel

This paper investigates the mechanical and wears resistance properties of AISI 5140 alloy steel coated with thin films of hydrogenated diamond-like carbon (HDLC) and titanium nitride (TiN). HDLC and TiN films were sputtered onto AISI 5140 alloy steel samples using the magnetron sputtering technique. In addition to coatings, the metallic substrates were also evaluated for hardness and wear resistance. The findings on wear losses, patterns, and wear trace widths were determined after the wear tests. In tribological tests, a variety of wear patterns were observed on both thin film coatings. The primary wear mechanisms of TiN coatings were found to be tribochemical wear, substrate material loss, and wear debris. However, the HDLC coating experienced wear due to ploughing action, with minor patches of the thin film being removed from the underlying material, but scanning electron microscopy observations showed no detectable wear. Using Raman spectroscopy, the structural properties of HDLC were analyzed, and the findings were compared to those of wear patterns. The results showed that the coating significantly improved the wear resistance of the AISI 5140 alloy steel and that the TiN-coated AISI 5140 alloy steel sample was more comparable to wear than the HDLC-coated AISI 5140 alloy steel sample. It is also shown that, as compared to an uncoated metallic substrate, the resilience of thin film coated components is a key factor impacting component life.