Abstract Scope |
Inconel Alloy 740H was the first age-hardenable nickel-based alloy approved by the ASME Boiler & Pressure Vessel Code for pressure-boundary applications and possesses a unique combination of high-temperature creep strength, corrosion resistance, and fabricability which enables improved designs up to temperatures of ~800C in comparison to traditional solid solution strengthened alloys, such as N06625, N06230, and N06617. Originally designed and tested extensively for advanced ultra supercritical (A-USC) steam power plant tubing and piping, it has been more recently applied to sCO2 power cycles, conventional steam cycles, and concentrating solar power demonstrations. As the application space for the alloy has expanded, the industry has experienced some expected 'growing pains' in the manufacturing of different product forms, shop fabrication, and field welding as many of the organizations are applying the alloy for the first time. Additionally, concerns with stress relaxation cracking during post-weld heat-treatment (also known as strain age cracking) have prompted recent research to understand the contribution of various factors influencing cracking. To disseminate these learnings and best practices to the industry, a new publicly available guideline for the procurement of 740H has been produced. This talk will highlight the history of the alloy, the shop and field experience with welding and fabrication, and the important contents of the guideline which go above and beyond the traditional code of constructions and basic welding procedures used today. |