# Influence of Tempering Temperature on Mechanical and Rotational Bending Fatigue Properties of 40CrNi2MoE Steel

## TL;DR

This study examines how tempering temperature affects the strength and fatigue life of 40CrNi2MoE steel, finding that higher temperatures reduce these properties due to changes in dislocation density.

## Contribution

The study identifies dislocation density as the key factor influencing fatigue life and strength in 40CrNi2MoE steel after tempering.

## Key findings

- Strength and fatigue life decrease with increasing tempering temperature.
- Dislocation density is the primary factor affecting the observed mechanical behavior.
- Fatigue fracture morphology remains largely unaffected by tempering temperature.

## Abstract

In order to examine the mechanical properties and rotational bending fatigue performance of 40CrNi2MoE steel subsequent to tempering at varying temperatures, the steel specimen was subjected to tempering within the range of 400~460 °C. SEM, EBSD, and TEM were used to analyze the microstructure as well as precipitates. The strain hardening law was studied using the modified Crussard–Jaoult method. Investigations were undertaken to reveal the rotational bending fatigue life with respect to the tempering temperature. The findings indicate that the strength and fatigue life of the examined steels exhibit a decline as the tempering temperature increases, with the primary factor affecting this trend being the alteration in dislocation density. No notable impact on the fatigue fracture morphology exerted by tempering temperature was found within the range of the experiment. The C–J model analysis reveals that the work-hardening behavior of the trial steels is influenced by dislocations and the second phase.