Development of welding and ultrasonic examination procedures for dissimilar metal welding between 10%Cr steel and Alloy 617M welded rotor of Indian advanced ultra super critical thermal power plant

Alloy 617M (a chemistry control variant of Alloy 617 / Inconel 617) and 10%Cr ferritic-martensitic steel are candidate rotor materials under consideration for steam turbine of Indian Advanced Ultra Super Critical (AUSC) coal fired power plants. There is a dissimilar metal welding (DMW) between 10% Cr steel rotor parts and Alloy 617M rotor parts. This DMW will be executed by hot-wire narrow-gap TIG (NG-TIG) welding process using Alloy 617 filler wire (ERNiCrCoMo-1). A procedure has been developed for thick dissimilar metal welding between 10%Cr steel and Alloy 617M for applications in welded rotor of Indian AUSC thermal power plant and is successfully demonstrated by fabrication of a 400 mm diameter and 95 mm thick dissimilar weld joint. For the volumetric inspection of the thick dissimilar weld joint, an ultrasonic phased array methodology is developed with beam focusing at different depths along the weld cross section. Inspection of the fabricated weld joint using the developed methodology confirmed that the weld joint is free from any defect equivalent to or larger than 2 mm SDH at any location in the buttering layer or weld volume