Development of nickel alloy based hardfacing procedure for fast breeder test reactor control rod sheath using conventional gas tungsten arc welding process and metal cored alloy grade ERC Ni Cr – B

Abstract

Fast Breeder Nuclear Reactors (FBR) will play a vital role to fulfill the power scarcity of developing India. The main products of the reactor assembly are manufactured using austenitic stainless steel - nuclear grades of AISI 316L. This material has excellent resistance to corrosion, better creep strength at higher temperature, and resistance to impact. Few reactor components are designed to perform rotation and translation movement for operation and control of reactor power. The relative motion between the components may lead to wear. Also, there is a possibility of self welding of these components due to high temperature and presence under a hot sodium working environment. Control rod sheath houses the control rod in a nuclear reactor which is used for raising or lowering the reactor output power. During operation of a nuclear reactor the control rod will move in and out. Due to this movement the control rod sheath will experience wear and tear. To reduce the wear and self welding problems throughout the operating period of the reactor, the components are designed with a layer of hard faced metal. Nickel based hard facing alloy is widely used for hard face coating in the nuclear reactor components. Since, it has high wear resistance under elevated temperature in the nuclear reactor. The process is done using Gas Tungsten Arc Welding (GTAW) by using the metal cored filler wire of grade ERC Ni Cr-B. Efforts have been put through this project for developing GTAW hard facing procedure and to observe the micro structure including micro hardness, macro hardness on coating as well as fusion zone and base metal.