Primary Cementite Network
The primary cementite network forms in high-carbon alloys as a brittle carbide phase during slower cooling. It severely deteriorates mechanical properties and requires post-weld heat treatment.
Physical-Chemical Mechanism of Action
The primary cementite network forms through rapid cooling of carbon-rich alloys, such as cast iron or steel. During cooling, carbon and iron condense into a brittle carbide, primary cementite. This process is particularly active at the austenite grain boundaries.
Metallurgical Relevance & Welding Risks
The occurrence of the primary cementite network leads to a significant loss of mechanical properties, such as toughness and hardness. The brittleness of the network can lead to cracks and hot cracks, especially under load. In addition, it can impair resistance to chemical corrosion.
Workshop Practice & Action Guidelines
To avoid or minimize primary cementite network, cooling should be controlled and slow. This can be achieved by using cooling water or special cooling media. For steels with high carbon content, a heat treatment (e.g., austenitization) is essential to dissolve the network and restore mechanical properties.