Hastelloy Intergranular Corrosion Resistance
The material resistance against selective attack along grain boundaries, achieved through optimized thermal processing and low carbon contents. It prevents carbide formation in sensitive temperature ranges.
Hastelloy is a highly alloyed material that gets its corrosion resistance mainly from its alloy composition. When welding, you have to be careful not to "burn" the alloy or put too much heat into it. If the material gets too hot or stays in a critical temperature range for too long, precipitates can form at the grain boundaries that ruin the corrosion resistance – that's called sensitization. Keep the heat input as low as possible and don't let the part cool slowly through the critical range after welding. Cleanliness is the be-all and end-all: any contamination, especially carbon or iron, can destroy the protective effect. If you have the parameters under control and work clean, the structure stays stable and the material retains its required properties.