In industry, thermochemical carbonitriding treatment is often followed by shot peening. Each of these processes generates surface microstructural modifications and residual compressive stresses which have a direct effect on the fatigue resistance. In the literature, these processes are often studied separately and therefore optimized independently.
This study focuses on these two processes, carbonitriding and shot peening, combined to better understand how they interact. For this, a complete analysis of different configurations was carried out, which includes the metallurgical characterization (microstructure, residual austenite level, residual stresses, microhardness) and the mechanical response through a campaign of mechanical tests.
Various analyzes have shown that the shot-peening of carbonitrided parts causes an increase in surface hardness, a transformation of the residual austenite and generates residual compressive stresses which depend on the level of residual austenite after carbonitriding. The test campaign has shown that shot peeing improves the mechanical properties of carbonitrided parts if a tempering step is carried out after thermochemical treatment.