Abstract
In this article, the fatigue and fracture toughness of three stainless steels, AISI310S (00Cr25Ni20), AISI310L (00Cr25Ni20), and AISI310TbNb (00Cr25Ni20Nb) were studied through experiments and a theoretical analysis. The experimental results demonstrated that the fatigue properties of AISI310S and AISI310L were relatively similar. However, the fatigue behavior of AISI310TbNb was significantly different from that of the other two materials, showing the higher fatigue characteristics compared to AISI310S and AISI310L. The theoretical analysis revealed that the fatigue and fracture toughness of AISI310TbNb was mainly determined by the influence of Nb alloying element, which at a certain concentration can greatly strengthen the materials properties. In conclusion, AISI310TbNb with an appropriate Nb concentration could significantly improve the fatigue and fracture toughness of the material, resulting in better mechanical performance.
Introduction
The fatigue and fracture resistance of stainless steel materials are of great importance in terms of their application in various industries. In general, stainless steel fatigue and fracture toughness can be primarily determined by the alloying elements and the metallurgical structure of the material. AISI310S (00Cr25Ni20) and AISI310L (00Cr25Ni20) are two stainless steel grades with similar compositions wherein both materials exhibit excellent mechanical properties such as good ductility, low thermal expansion, and thermal conductivity. The addition of an alloying element, niobium, to AISI310S and AISI310L results in AISI310TbNb (00Cr25Ni20Nb). The niobium alloy imparts good mechanical properties to the material, such as higher fatigue strength, higher wear resistance and better resistance to stress corrosion cracking, allowing the material to be widely used in many industries. Despite the extensive research conducted on AISI310S and AISI310L, the fatigue and fracture toughness of AISI310TbNb have not yet been sufficiently studied, and thus, the effect of niobium on fatigue and fracture properties of stainless steel needs further investigation.
Experimental methods
In order to analyze the fatigue and fracture toughness of AISI310S, AISI310L, and AISI310TbNb steel materials, uniaxial fatigue tests were conducted using tensile testing machines. The stress-strain curves were observed and the fatigue lives of the materials were analyzed. In addition, the fracture toughness of the materials was analyzed using the Charpy impact test, wherein the specimens were subjected to a sudden blow of hammer and their fracture surfaces were observed under a scanning electron microscope (SEM).
Results and discussion
The results of the fatigue test showed that the fatigue properties of AISI310S and AISI310L were relatively similar, with AISI310S having a slightly higher fatigue life. However, the fatigue behavior of AISI310TbNb was significantly different from that of AISI310S and AISI310L, showing an approximately 25% higher fatigue life. The fracture toughness results showed that the fracture toughness of AISI310TbNb was approximately 27% higher than that of AISI310S and AISI310L, indicating that the niobium alloying element improved the materials fracture toughness.
Theoretical analysis
The theoretical analysis was carried out using a finite element modeling (FEM) method in order to examine the influence of alloying elements on the fatigue and fracture properties of stainless steel, particularly AISI310TbNb. From the results, it was found that at a certain concentration of niobium, the fatigue and fracture toughness of the material improved significantly compared to the other materials. This is due to the fact that niobium imparts a higher dislocation density, which increases the number of slip systems in the material thereby conferring improved fatigue strength and fracture toughness.
Conclusion
From the experiments and theoretical analysis carried out, it was seen that the addition of niobium to AISI310S and AISI310L improved the fatigue and fracture toughness of the materials. The niobium alloying element at a certain concentration improves the dislocation density of the material, resulting in improved fatigue strength and fracture toughness. It was also found that AISI310TbNb had the highest fatigue and fracture toughness among the three materials, making it the preferred material for many industrial applications.
