Creep Rupture Behaviour of Alloy 625 Nickel-Base Superalloy Casting for Advanced Ultra Supercritical Power Plant Applications

Abstract

In the twenty-first Century, the world especially India faces the critical challenge of providing abundant, and cheap electricity to meet the needs of a growing global population, while at the same time, preserving environmental values which are very important. Traditional methods of coal combustion emit pollutants (including CO₂) at high levels relative to other power generating options. Maintaining coal as a generating option will require methods for addressing these environmental issues. To reduce CO₂ emissions, research and development on Advanced Ultra Super Critical (AUSC) power generation is ongoing to enhance the efficiency of a coal-fired power generation. In an AUSC plant, it is considered to use Nickel-base superalloys with higher strength capabilities at elevated temperature conditions in addition to conventional heat-resistant steel. Alloy 625 nickel-base superalloy is selected for the steam turbine casing in AUSC power plant applications because of its better properties. In higher temperature domain, Creep is one of the major properties to be assessed for the material to be used in AUSC power plants. Creep rupture tests along with other mechanical tests were conducted on Alloy 625 cast material at elevated temperatures to generate the data for design applications. In this paper, creep behaviour of Alloy 625 is presented at various stress and temperatures and microstructures are correlated along with other mechanical properties.