Experimental investigation of the solid particle erosion behavior of Cr/Cr ₂ O ₃ and Cr/H ₂ SO ₄ coatings using ex-situ digital image analysis

This study experimentally investigated the solid particle erosion behavior of black chromium (Cr/Cr 2 O 3 ) and white chromium (Cr/H 2 SO 4 ) coatings deposited on St37 steel under different impact angles, temperatures, and particle loads. The main objective of the study was to determine the influence of coating type on erosion resistance and to quantitatively evaluate surface damage using Ex-situ digital image analysis (DIA). Erosion tests were carried out under 3 bar air pressure at impact angles of 30° and 45°, temperatures of 22°C and 50°C, and particle loads ranging from 2.5 to 25 kg. Experimental results revealed that chromium coatings significantly reduced erosion-induced weight loss compared with uncoated St37 steel, while white chromium coatings generally exhibited the lowest wear loss. Increasing temperature improved erosion resistance, particularly for white chromium-coated samples. In addition to conventional weight loss measurements, heat maps, pixel intensity histograms, and GLCM-based texture analyses were employed for quantitative and image-based characterization of surface damage. Furthermore, Pearson correlation and one-way analysis of variance analyses confirmed that coating type had a statistically significant effect on erosion behavior ( p < .05). The obtained results demonstrated that the ex-situ DIA approach can effectively support conventional erosion analyses for quantitative surface characterization.