A novel procedure for fabrication of wear-resistant bushes for high-temperature application

Wear-resistant bushes, for high-temperature application, made of hardfacing alloys are required in various components for in-sodium service in the prototype fast breeder reactor (PFBR). For this purpose, bushes of Colmonoy 6, a nickel-base high-temperature wear-resistant hardfacing alloy, have been fabricated using a novel procedure involving weld deposition of the hardfacing alloy on austenitic stainless steel (SS) rods by the gas tungsten arc welding (GTAW) process followed by precision machining of the hardface deposits. Ultrasonic examination of the hardface deposits and the machined bushes, as also achieving the dimensional tolerance and surface finish on the bushes as per specification, confirmed the success of this fabrication procedure. Microstructural examination showed uniform distribution of precipitates throughout the thickness of the bush. The hardness obtained across the thickness and along the surface of the bush was well above the specified limit of 540 VHN (52RC). Dimensional measurements after fabrication and thermal ageing at the service temperature of 823 K for 24 h and 1000 h confirmed dimensional stability of the bushes fabricated using the above procedure.