Cementite precipitation
Cementite precipitation is the process where hard iron carbide phases form from supersaturated solid solutions or unstable phases decompose. This affects the wear behavior and hardness of the steel.
Physical-Chemical Mechanism of Action
Cementite precipitation occurs when too many carbon atoms are present in supersaturated solid solutions. These atoms then form iron carbide (Fe3C), a very hard phase. Alternatively, unstable phases like martensite decompose and also produce iron carbides.
Metallurgical Relevance & Risks in Welding
Cementite precipitation can lead to increased wear and hard spots in the material. These hard areas can cause cracks, especially under mechanical stress. They also negatively affect weld strength.
Workshop Practice & Action Guidelines
To minimize cementite precipitation, control the carbon content in the steel. Careful cooling is required under heavy loads and high temperatures. If needed, use stabilizing additives like niobium or titanium to prevent cementite formation.