Contact-Based Wear Modeling of Coated Deep Bores Manufactured by Electrochemical Rifling

This study presents an analytical–experimental investigation of the mechanical and tribological behaviour of two coating systems applied to deep, internally profiled cylindrical components manufactured via Electrochemical Rifling (ECR): a hard anodised aluminium oxide (AAO) coating on an aluminium alloy and a hard chromium coating on alloy steel. The experimental characterisation includes microhardness measurements, coefficient of friction determination, and controlled sliding wear tests. The results indicate that the chromium coating exhibits approximately 3.2 times higher microhardness and a 16% lower average coefficient of friction compared to the anodised aluminium layer, leading to significantly improved wear resistance.A good agreement is observed between analytical predictions and experimental results. For the steel specimen, values of approximately 26,800 cycles (analytical) and 36,000 cycles (experimental) were obtained, while for the aluminium specimen the corresponding values are approximately 2,050 and 2,012 cycles.Considering the degradation mechanisms typical of hard chromium coatings, a conservative reliability-oriented criterion yields a functional service life of approximately 12,000 cycles for the chromium coating and around 1,000 cycles for the anodised aluminium coating. A Weibull-based reliability analysis (R = 0.95) indicates service lives of approximately 5,200 cycles and 433 cycles, respectively.