Hastelloy intergranular corrosion
Hastelloy intergranular corrosion is a selective corrosion type in nickel alloys, caused by improper thermal exposure. Local depletion at grain boundaries leads to cracked weld areas.
Physical-Chemical Mechanism of Action
Hastelloy intergranular corrosion occurs in nickel alloys when they get improperly hot. Local depletion of chromium or molybdenum at grain boundaries leads to selective attack of the material. This can be caused by incomplete melting or insufficient cooling time during welding.
Metallurgical Relevance & Welding Risks
This corrosion leads to cracked and missing weld areas, which severely affects the mechanical strength of the joint. It can also lead to reduced component life. The risk is especially high at elevated temperatures and with insufficient cooling.
Shop Practice & Action Guidelines
To avoid Hastelloy intergranular corrosion, the weld must be carefully cooled. The cooling time should be at least 10 seconds to ensure uniform alloy depletion. Temperature control during welding is crucial to avoid incomplete melting.