Martensitic Hardening Microstructure
Martensite is a hard, forced-distorted crystal lattice in steels formed by rapid cooling. It increases strength and wear resistance but can also lead to cracking.
Physical-Chemical Mechanism of Action
Martensite forms when steel is overheated in the molten phase and rapidly cooled. The rapid cooling prevents diffusion-based transformation and traps carbon at the grain boundaries. This results in a distorted, supersaturated solid solution with high carbon content.
Metallurgical Relevance & Welding Risks
Martensite is known for its very high strength and wear resistance. It is often used in highly stressed parts like axles or gear shafts. However, martensite can also lead to cracking, especially if cooling is too fast. This can cause hot cracks or quench cracks in the material.
Workshop Practice & Action Guidelines
To avoid or control martensite in steels, it is important to regulate the cooling curve precisely. For highly stressed parts, a slow and controlled cooling (often using cooling water or cooling oil) should be applied. For special applications where martensite is desired, cooling can be accelerated to produce the desired structure.