Carbon carbide phase precipitation
Carbon-carbide phase precipitation is the process where carbon precipitates as carbide particles in the weld. This increases the hardness and wear resistance of the steel.
Physical-Chemical Mechanism of Action
Carbon-carbide phase precipitation occurs when carbon precipitates as carbide particles (like cementite) in the weld. This happens due to excess carbon in the solid solution and tempering.
Metallurgical Relevance & Welding Risks
Precipitation of carbon-carbide phases increases hardness of the weld, improving wear resistance. However, too high a concentration of carbide particles can lead to increased stress concentration, which can cause cracking and hot cracking in the material. Furthermore, precipitation can lead to an uneven structure that impairs mechanical properties.
Workshop Practice & Action Guidelines
To achieve optimal carbon-carbide phase precipitation, it is important to design the welding process such that carbon precipitates as carbide particles in the weld. This requires correct selection of steel with the right carbon content and application of welding parameters that support the tempering process. Temperature and time in the critical temperature window (t8/5) should be precisely controlled to ensure uniform precipitation.