Session: MF-25-01 High Strength Steels for Pressure Vessels and Piping Applications

Paper Number: 105615

105615 - Age-Hardened Nickel-Base Alloys for Power Piping 

Age hardened nickel-base alloys began to be seriously considered for power piping in the late 1990s in the European Thermie project to develop materialstechnology for Advanced Ultra-supercritical (AUSC) coal fired power boilers. It was recognized at that time that conventional ferritic and austenitic boiler tube would necessarily require unrealistically large wall thickness at the temperatures and pressures specified for AUSC. Only age hardened nickel-base alloys appeared to provide the required combination of creep strength, hot corrosion and oxidation resistance and weldability. Over the next decade projects were initiated in manycountries to characterize new and legacy alloys for this application. The results of this work were widely shared internationally and served as a data basis for neweradvanced energy technologies such as supercritical CO2, Gen 3 concentrating solar and Gen 4 nuclear. This work gradually filled in major uncertainties such asability of alloy producers to manufacture tube, pipe and fittings in a wide range ofsizes, microstructure stability for times relevant to power plant design life, field weld fabrication and certainty about availability and cost. Several alloys have been standardized and approved by applicable code bodies for use as welded power piping. Over the past decade several private and publicly funded test loops and pilot plants designed for service at 700 C or above have been constructed with age-hardened alloy piping and operated in test mode. Recently, the US Department of Energy funded a project to demonstrate the US capability to manufacture full-scale components for an AUSC plant. Other D0E funded projects have assessed the weldability of age-hardened piping alloys, with emphasis on preventing stress relief cracking. Guidelines for shop and field welding have been developed.The associated data and literature provide a significant knowledge base to assess the status of this technology and prospects for the future. This paper summarizes achievements to date using primarily examples for UNS N07740, but with reference to published data on similar alloys. Specific challenges for future widespread use of these alloys are defined.

Presenting Author: John deBarbadillo special metals

Presenting Author Biography: John deBarbadillo is Chief Metallurgist at Special Metals, a PCC Corporate Engineering Fellow, and a Fellow of ASM International. He has over 55-years' experience with development, manufacturing and applications for nickel and nickel-base alloys. He is located at the Special Metals plant in Huntington WV.

Authors:

John deBarbadillo special metals