Improving in microhardness of C45 steel obtained via electron beam hardening using a one-factor-at-a-time technique

Abstract

This article presents a novel electron beam hardening (EBH) process for C45 steel cylindrical specimens in an as-received state, utilizing continuous irradiation with power in the range of 720–2070 W and line scanning in the axial direction. The influence of operating parameters (i.e., electron beam current, workpiece velocity, scanning frequency, and focal length) on microhardness is examined using a one-factor-at-a-time technique. Scanning electron microscopy images reveal pronounced surface transformation hardening of C45 steel, resulting in martensite transformation and the formation of a pseudo-amorphous structure in the surface layer. The maximum surface microhardness obtained, HV_0.05=903, is three times greater than that achieved after turning (the step before EBH). The electron beam current and workpiece velocity significantly influence the thermal processes in the surface layers and, consequently, the microhardness. Based on the experimental results, the optimal ranges of the operating parameters have been defined.