These carbides often form as continuous networks within the microstructure, depleting the surrounding area of chromium and severely compromising corrosion resistance and ductility.
Materials susceptible to weld decay are typically austenitic stainless steels and nickel alloys containing more than 0.02% carbon, as well as weld metals used in joining these materials.
Factors that promote weld decay include:
- High carbon content in the base material or weld metal
- Prolonged exposure to elevated temperatures within the critical temperature range
- Certain microstructures, such as duplex or ferritic-austenitic structures, which are more prone to carbide precipitation
- Welding processes that involve slow cooling rates, such as gas metal arc welding (GMAW) or shielded metal arc welding (SMAW)
To mitigate weld decay, several strategies can be employed such as:
- Selecting low carbon filler metals and base materials
- Controlling welding parameters to minimize heat input and cooling times
- Applying post-weld heat treatments (PWHT) to dissolve and redistribute carbides
