Comparison to Micro Wear Mechanism of PVD Chromium Coatings and Electroplated Hard Chromium

Electroplated hard chromium (EPHC) has been widely used in industry due to its excellent mechanical properties, but the development of this technology is limited by environmental risks. The physical vapor deposition (PVD) process has shown promise as an alternative to EPHC for producing chromium-based coatings. In this research, we investigate the microstructure and wear resistance of pure chromium coatings using two PVD techniques, namely, magnetron sputtering ion plating (MSIP) and micro-arc ion plating (MAIP), which are compared to EPHC. To assess wear resistance, we evaluated factors such as hardness, coating base bonding force, wear rate and friction coefficient via friction and wear experiments. The results show that, in terms of microstructure, while the EPHC coating does not exhibit a strong preferred growth orientation, the PVD coatings exhibit an obvious preferred growth orientation along the (110) direction. The average grain size of the EPHC coating is the smallest, and the PVD chromium coatings show a higher hardness than the EPHC coating. The results of pin-on-disk tests show that there is little difference in friction coefficients between EPHC and MAIP chromium plating; however, the MAIP chromium coating showed an excellent specific wear rate (as low as 1.477 × 10^-13 m³/Nm). The wear condition of the MAIP chromium coating is more stable than that of the EPHC coating, indicating its potential as a replacement for EPHC.