Understanding the role of glaze layer with aligned images from multiple surface characterization techniques

Abstract A glaze layer that significantly reduces friction and wear has been found on the surface of many Fe-, Cr-, and Ni-based material systems undergoing fretting/sliding at elevated temperature. In this paper, we propose a novel way to understand the role of glaze layer using computer vision algorithms. Two workflows, one for quantitative glaze layer identification and the other for image alignment, have been developed. For glaze layer identification, we used computer vision concepts that considers the color and reflection of glaze layer under optical microscope (OM). For image alignment, we developed a strategy to conduct pixel-to-pixel alignment of images acquired by multiple techniques (e.g., OM, scanning electron microscopy, 3D optical profilers) with sub-pixel error. As such, the correlation between the height map and locations of the glaze layer within the wear scar can be readily determined. These methods are used to evaluate wear scars generated on 310S stainless steel under like-on-like, cylinder-on-flat fretting conditions from 20°C to 700°C. The glaze layer is found to always occupy relatively high locations within wear scar. With temperature rise, the projected coverage of glaze layer follows the same increasing trend with three distinguishable stages, and the threshold temperature of the three stages matched with severe-to-mild wear transition. These results provide evidence that severe-to-mild wear transition resulted from spreading of glaze layer coverage, and glaze layer may reduce friction and wear by reducing real contact area.