Microstructure-erosion resistance correlation in high chromium cast iron: a digital image processing approach

Abstract

High chromium cast irons (HCCIs) are widely employed as wear-resistant hardfacing materials in industrial applications where solid particle erosion (SPE) represents a primary degradation mechanism, such as in energy production, mining, and cement manufacturing. The erosive wear resistance of these alloys is strongly dependent on the microstructural features of the primary $M_{7}C_{3}$ carbides, particularly their size, morphology, and spatial distribution within the metallic matrix. The quantitative relationship between carbide distribution homogeneity and erosion resistance has received limited attention in the literature. This study investigates the erosive wear resistance of a Fe-Cr-C cast iron hardfacing alloy and proposes three digital image processing methods to quantitatively characterise the carbide microstructure and correlate it with experimental erosion test results. Optical microscopy combined with image binarisation was used to segment primary $M_{7}C_{3}$ carbides. Three methods were adopted: carbide volume fraction (CVF), minimum inter-carbide distances, and a moving scanning area approach. Erosion tests were conducted according to ASTM G76 guidelines using two Arizona road dust powder grades with two mean diameters under equal kinetic energy conditions. Results show that the erosion rate decreases significantly with the increasing erodent particle size and that carbide distribution homogeneity plays a critical role in determining the erosion resistance. The moving scanning area method proved particularly effective at correlating microstructural coverage with experimental erosion rates.