Experimental Investigation of White Layer in Grinding of AISI 52100 Annealed Steel

Abstract

Ground white layer is caused primarily by grinding temperature induced phase transformation. So, it may form when grinding temperature exceeds the nominal phase transformation temperature. However, no attempt is made to investigate mechanical effect on formation of white layer. In this study, grinding temperature is measured by using thermocouple technique in grinding of AISI 52100 annealed steel. The specimens are investigated by using scanning electron microscope (SEM), energy disperse spectroscopy (EDS), micro hardness tester and X-ray diffraction (XRD). The microstructure and formation mechanism of white layer are analyzed. Ground whiter layer is confirmed to be composed of fine-grained cryptocrystalline martensite and retained austenite. High hardness of white layer is caused by transformation hardening through fine grain and high dislocation density due to severe deformation. White layer can form at temperatures below the nominal austenitization temperature of the material. Plastic deformation is also important in white layer formation during grinding process. High pressure on grinding surface exists under severe deformation. Phase temperature can be reduced due to high pressure; while crystal grain can be refined by plastic deformation. Oxidation and carburizing phenomenon exist during formation of white layer.

Molecular dynamics simulation of the gun barrel material erosion by propellant gas

“…The main components of gas CO, O2, and NO were measured in real-time through a gas collection and measurement device and a closed explosive device by Hu et al [1]. Huang et al [2] analyzed the microstructure and retained austenite of the white layer by scanning electron microscope (SEM) and X-ray diffractometer (XRD), and discussed the formation mechanism of the white layer. Li et al [3] believed that the propellant gas caused the molten layer continuously formed on the inner wall of the barrel to be taken away by the high-speed airflow, resulting in the expansion of the inner diameter of the barrel.…”