Progression of high-adherent hard chromium-based coating on cast iron exploiting cathodic-arc PVD technique for higher wear resistance

The development of hard coating layers emerges as a promising avenue to promote surface properties such as hardness, wear resistance, and, hence, lifetime. Metal nitrides, especially Cr-based, are among the array of available coating materials that stand out for their exceptional tribological performance and chemical stability, particularly at elevated temperatures. In this research, a promising CrNiAlSiN coating is deposited on cast iron substrates to promote the performance and durability of different components made from cast iron in wide applications such as engines parts, gears, and hydraulic components. To promote the adhesion strength, different substrate surface roughness was prepared using emery papers with four different grit sizes (#60, #240, #400, and #800) and denoted as CI-60, CI-240, CI-400 and CI-800. The hardness, wear resistance, and adhesion strength of CrNiAlSiN hard coating were evaluated. The cross-section examination of the coating layer revealed homogeneous, dense, and defect-free CrNiAlSiN coatings with approximately 11 μm thickness. It was found that the highest surface roughness (CI-60) exhibited the lowest failure load (2971.17 mN) and hardness (2272.38 ± 61.96 HV0.2), while sample CI-240 demonstrated the highest failure load (3814.19 mN) and hardness (3533.30 ± 50.73 HV0.2). Meanwhile, the lowest wear rate (0.69 × 10⁻⁹ mm³/N.m) was recorded for sample CI-60, while CI-240 recorded a wear rate of 1.07 × 10⁻⁹ mm³/N.m; however, the samples CI-400 and CI-800 recorded significant increase in wear rate 1.47 × 10⁻⁹ and 3.6 × 10⁻⁹ mm³/N.m, respectively. This implies that substrate surface roughness using emery paper has a significant impact on the adhesion strength, hardness, and wear resistance of the hard Cr-based coating.