Fatigue Life Analysis of Traditional and Annealed AISI 304L Specimens by Thermographic Methods

AISI 304L is a low-carbon austenitic stainless steel widely used in common engineering applications, according to its good mechanical properties such as high ductility, corrosion resistance, and easy weldability. This material is adopted in various environmental conditions, such as pressure vessels or in pipelines where fluid temperature variations occur and affect its mechanical behavior. Nowadays, the applications of advanced investigation methodologies, such as infrared thermography, are widely adopted for the rapid analysis of the fatigue properties of common materials, especially metals. In this work, fatigue properties were evaluated on AISI304L specimens having two different microstructural states, one in the as-received condition and the other one after solution annealing. Fatigue test campaigns were performed with the application of the Risitano Thermographic Method. The microscopic analysis highlights the differences in the microstructure before and after the heat treatment. The characteristics of the microstructures are the main ones responsible for the different fatigue behavior obtained with experimental tests. The Thermographic Method proved to be a valid rapid approach for the fatigue analysis, confirming that the annealing process led to an improvement in the fatigue strength of the material.