Study of Heat Affected Zone of a Weld in 9Cr-1.8W-0.5Mo Steel for Power Plant Application

Abstract

Continuous improvement in steam parameters for achieving higher efficiencies led to the development of many new creep resistant steels in thermal power plant industry. As welding is the major fabrication technique used in power plant construction, these creep resistant steel should possess good weldability and in-service life condition. This thesis contains a presentation of basic problems appears in service at Heat Affected Zones (HAZs) of membrane panels and high temperature pipe lines made of tempered bainitic/martensitic creep resistant 9Cr-1.8W-0.5Mo (Grade 92) steel used for boilers operating at supercritical parameters. The HAZs of these components often experience Type-IV creep crack due to micro-coalescence of creep voids at operating temperature. Welding thermal cycles had been simulated with Finite Element Simulation using SYSWELD and with these thermal cycles physically HAZs had been simulated and studied for its microstructure, hardness and toughness in-situ comparison with real time HAZ during welding. The experimental results will be used to study the creep failure to develop a further modification in the parent metal, which can serve as a bench mark for the future development of creep strength enhanced steels