A CHANGE IN THE MICROHARDNESS OF A SURFACE-HARDNED SHAFT DEPENDING ON HARDENING MODES

Abstract

This study investigates the variation of microhardness in the surface layers of hardened shafts along the longitudinal direction, with the objective of optimizing the surface plastic deformation process for structural steel 40X. The research aims to determine the most effective deformation parameters that enhance the load-bearing capacity and durability of critical machine components. To achieve this, samples were subjected to surface plastic deformation using forces of F = 100, 200, 300, 400, and 500 N, combined with feed rates of S = 0.05; 0.10, and 0.155 mm/rev. The process induced inclined platforms on the sample surfaces, providing a means to perform precise microhardness measurements along the deformed layers.

The experimental results demonstrate that both the applied force and the feed rate significantly influence the distribution and magnitude of microhardness across the surface layer. Graphs illustrating the dependency of microhardness (HV) on the deformation parameters were constructed, and corresponding regression equations were derived to characterize the observed relationships. These mathematical models offer predictive capability for tailoring deformation conditions to specific engineering requirements.

The primary goal of this work is to establish an optimal processing mode for surface plastic deformation that ensures the desired hardness profile and mechanical performance over the entire service life of the part. The outcomes are valuable for designing more durable components in high-load environments, contributing to enhanced reliability and reduced maintenance in mechanical systems. This research holds particular relevance in industries such as automotive, aerospace, and heavy machinery manufacturing, where material strength and longevity are critical. In this context, the scientific approach adopted in the study—combining experimental methods, statistical modeling, and mechanical analysis—provides a robust foundation for advancing modern surface hardening technologies, and demonstrates the potential for extending these findings to other alloy systems and geometrically complex components.