MECHANICAL PROPERTIES OF DISSIMILAR METAL JOINTS USED IN POWER PLANTS

Abstract

In the past 100 years of industrial development thermal /fossil fuel fired power plants have played a major role. But releasing of pollutants from these have always been a challenge considering the environment prospective. To decrease the impact steam pressure and temperature have been continuously raised to improve the efficiency. Advanced ultra-supercritical power plants are the utmost requirement for the future from the environment and growing energy demand point of view. Thus taking the temperature and pressure in the range of 720-750℃ and pressure above 34.5 MPa. Materials to be used for AUSC technology should have excellent creep strength, corrosion resistance and fabricability. While nickel alloy namely IN617 and 740 are proposed for this purpose, but they are very expensive. Thus alternate creep resistant materials like ferritic and austenitic steels can be used at lower temperature zones. So that cost can be reduced. To use Nickel alloy and creep resistant steels within the same power plant. Dissimilar metal welds between the two types of material are inevitable. As Dissimilar metal welds are more prone to failure compared to similar metal welds due to compositional and structural gradients, it becomes critically important to investigate and improve upon the integrity of the dissimilar weld joint between nickel alloys and ferritic and austenitic steels. In this project, attempt is made to analyse the properties and cause of failure of weld joints between Inconel 617 and SUS304H. Tensile test at room temperature, Hardness of weld, creep test at operating temperature are performed along with microstructure.