Incoloy 800H, a heat-resistant iron-nickel-chromium alloy, is designed for use at elevated temperatures. However, at temperatures ranging from 550°C to 750°C (1022°F to 1380°F), this alloy can be susceptible to a phenomenon known as stress relaxation cracking (SRC). Let’s delve into the challenges associated with SRC in Incoloy 800H and explore mitigation strategies.

1. Understanding SRC Mechanism:
   • Stress relaxation cracking occurs due to the gradual reduction of internal stresses within a material over time.
   • In the case of Incoloy 800H, these stresses can accumulate during fabrication processes such as welding, forming, or heat treatment.
   • The alloy’s composition and microstructure play a crucial role in determining its susceptibility to SRC.
2. API Technical Report 942-B Recommendations:
   • The American Petroleum Institute (API) provides guidelines to mitigate SRC in high-temperature alloys.
   • These recommendations cover material composition, fabrication, and heat treatment.
   • However, obtaining material that precisely adheres to these prescriptions can be challenging.
3. Complexities in Alloy Composition and Fabrication:
   • Thicker Wall Piping: Special situations, such as thicker wall piping, demand careful alloy selection and fabrication.
   • Dissimilar Metal Welds: Joining Incoloy 800H to other materials (dissimilar metal welds) requires intricate welding procedures.
   • Welding Challenges: Welding Incoloy 800H demands precise control of heat input and post-weld heat treatment.
   • Material Sourcing: Ensuring material compliance with API recommendations can be elusive.

Keep reading, Happy welding…