Study of plasma-hardened wheel steel using nanoindentation

Abstract

The necessity and possibility of using nanoindentation in studying the physical and mechanical properties of plasma-hardened wheel steel are considered. The goal of the study is demonstration and substantiation of significant differences in the mechanical properties and behavior of the materials in nanoscale tests from those determined in traditional macroscopic tests. The method was implemented using a NanoHardnessTecter nanohardness tester. The electric field formed in the nanoscale hardness tester pressed on the indenter and the diamond tip of the indenter is immersed in the surface layer of the material under study. The characteristics of the surface layer are determined using the developed software. Knowledge of the physicomechanical characteristics of the material (hardness, Young’s modulus, elastic recovery, etc.) which affect the wear resistance of the surface layers, allows one to evaluate and select the optimal surface modification technology using plasma hardening. The credibility of determination depends on the parameters of measuring equipment and compliance with the requirements to the depth of the imprint depending on the thickness of the hardened layer. The studies were carried out on the samples cut from the rim and crest of a railway wheel subjected to surface plasma hardening on a UPNN-170 installation (Russia). It is shown that the hardness (according to VickersHVandH) of the rim is greater, and Young’s modulus, on the contrary, is less than the corresponding characteristics of the crest. Moreover, the wear resistance of hardened structural steel increases after nanostructural friction treatment.