Austenite phase transformation of SKD11 by surface heat treatment with a focused electron beam

Recently, many studies have been actively conducted to improve the mechanical properties of metallic materials through surface heat treatment with an electron beam. Thermionic focused electron beam equipment is mainly used in industrial manufacturing machines such as e-beam welders. However, such equipment is expensive, and the filament lifetime is limited. In this study, the austenite transformation in an iron matrix was investigated after surface heat treatment of SKD11 with plasma diode focused electron beam equipment, which is a recently developed alternative based on a plasma diode cold cathode. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results revealed that the iron matrix transformed to an austenite structure without Cr-rich carbide formation. After the surface heat treatment using the plasma diode focused electron beam equipment, a positive residual stress was confirmed by XRD residual stress measurements. This result was obtained because impurities in the iron matrix such as carbon existed in alloy form rather than composite form. The average hardness at a depth of 300 μm from the surface was measured to be approximately 480 Hv.