Hastelloy weld metal solidification
Hastelloy weld metal solidification is a crystallization process for nickel-chromium-molybdenum melts, where segregation of trace elements affects crack resistance.
Physical-Chemical Mechanism of Action
Hastelloy weld metal solidification is a crystallization process where nickel-chromium-molybdenum melts solidify in a dendritic pattern. During solidification, segregation of trace elements like cobalt, niobium, and titanium occurs, affecting the microstructure.
Metallurgical Relevance & Welding Risks
These segregations can lead to uneven hardness and crack resistance. Too high cobalt content can lead to increased solidification temperature and thus higher risk of hot cracking. Excessive niobium or titanium segregation can coarsen the structure and reduce toughness.
Workshop Practice & Instructions
To ensure homogeneous solidification, it's important to control the melting process. This involves optimal melt temperature and a constant cooling rate. The melt time should not be too short (at least 30 seconds) to ensure complete solidification. When selecting the weld metal, consider the specific requirements of the part and the intended application.