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The heat treatment of HASTELLOY® B-3® (UNS N10675) is a critical process, as both heating and cooling must rapidly pass through the 475°C embrittlement zone and the formation of high-temperature σ phase and other intermediate phases. Therefore, rapid heating and cooling of the workpiece are essential. Generally, it is required to preheat the furnace to the designated temperature before placing the workpiece in the furnace. It is necessary to clean the surface of the workpiece before loading it into the furnace. After a certain period of insulation, it should be quickly water quenched.
Unless specifically requested by the customer, all B-3 alloy forgings are supplied in the solution-treated condition. The temperature for solution treatment of B-3 alloy is 1065°C (the solution treatment temperature should be controlled within 1060-1080°C), followed by rapid quenching. Thin plates or wires are bright annealed at a heating temperature of 1150°C, followed by cooling in hydrogen to obtain the best corrosion resistance.
The temperature of the solution treatment is relatively high, and rapid cooling is required afterward, resulting in inevitable deformation of the workpiece. During the heat treatment of B-3 alloy, attention should also be paid to the following issues: to prevent deformation of equipment components during heat treatment, stainless steel reinforcement rings may be used; strict control should be exercised over furnace loading temperature, heating and cooling time; pre-treatment of heat-treated parts should be carried out before loading into the furnace to prevent thermal cracking; after heat treatment, 100% penetration testing should be performed on the heat-treated parts; if thermal cracking occurs during the heat treatment process, the affected areas should be ground and welded using specialized welding techniques.
