Carbon Diffusion Behavior Analysis Using Electron Probe Micro-Analyzer in the Carburized Chromium-Molybdenum Alloy Steel

Abstract

The effect of carburizing conditions on the carbon diffusion of carburized chromium molybdenum steel was studied by using EPMA analyzer and x-ray diffractometer. And the carburized structures were compared with the XRD structure change analysis and Carburizing changes were analyzed from the results of EDS analysis obtained using SEM.

After gas carburizing, the specimens were cut and mounted, and the carbon content changes in the depth direction were measured. Carburization of the pump drive hub was maintained at 930℃ for 2 hours and diffusion at 930℃ for 1 hr. Carburization of the sprocket was maintained at 890℃ for 1 hour and diffusion at 890℃ for 20 minutes. And the carbon potential of the driving hub was maintained at 0.9 wt% at the carburizing temperature and 0.75 wt% at the diffusion temperature. The carbon potential of the sprocket was maintained at 0.9 wt% at the carburization temperature and 0.7 wt% at the diffusion temperature.

EPMA analysis was performed on the carburized surface to obtain the spectra of C, Fe, Cr, Mn, and Mo. As a result, the carbon content was showed at a maximum from the surface to about 350 microns, and the carburization gradually decreased toward the inside.In the vicinity of the surface containing a large amount of carbon, Cr was bonded to carbon and Cr carbides were formed, so that Cr content was increased.These results were similar to the EDS analysis results obtained from the SEM analysis.

The carbon content of the SCM-420 before carburization was 3.72 wt.%, And the carbon content after carburization was 5.81 wt.%, Which was 156% higher than that before carburization. And in the case of SCM-415, the surface carbon content was 5.48 wt.%, Which was increased from 3.97 wt.% Before carburization to 1.51 wt.% After carburization.

Keywords: Electron Prove Micro-Analyzer, EDS,Chromium-Molybdenum Alloy Steel, Carburization, Diffusion, XRD