In a study, phD student Katerina Chantziara has investigated what causes steel fatigue and what makes it break. The aim of the research is to contribute to improved durability.
– I have studied different martensitic tool steels and examined what happens inside the material when it is subjected to stress, and what ultimately causes it to fracture, says Katerina Chantziara, PhD student in physics.
Martensitic tool steels are used in various environments, and their structure is constantly being improved through new material blends and processing techniques. However, these improvements can also create new types of defects, making it important to understand how the steels are affected by fatigue. Martensite is a particular phase in steel that arises when austenite (another structure in iron) is cooled so quickly that the atoms do not have time to move through diffusion. The result is a deformed crystal structure (called body-centered tetragonal, BCT) that gives the steel extreme hardness but also makes it more brittle.
In the study, six modern high-strength tool steels of two main types were examined:
- Cold-work steels: manufactured using powder metallurgy and processed through pressing and forging.
- Hot-work steels: produced through traditional casting and forging or by additive manufacturing.
– I compared the steels in terms of strength, structure, defects, and fatigue resistance, and analyzed how cracks form and grow, says Katerina Chantziara. The goal is to contribute new knowledge that can help industry develop tool steels that perform better under long-term stress.
Read more here: PM tool steels: microstructure, defects and Very High Cycle Fatigue
