Development of repair welding procedure for a CA-15 casting of a pump impeller

Abstract

Repair welding procedure has been developed for a CA-15 (equivalent to AISI 410) martensitic stainless steel casting of a pump impeller. The repair welding qualification procedure for this material involves metallurgical investigations of bead-on-plate deposit of Inconel 82 (AWS ER NiCr-3) on a piece of the cast CA-15 material and autogenous welding of the cast material. Metallurgical investigation confirmed that mechanical properties of the weld metal with matching composition is inferior, where as properties with Inconel 82 weld is comparable to that of the base metal. Post weld heat treatment (PWHT) carried out both at 873 K for 1 h and at 1008 K for 1 h reduced the hardness in the heat-affected zone (HAZ) to nearly that of the base metal. PWHT at 873 K for 1 h was recommended for repair for ease in achieving this temperature during localized PWHT. Tests carried out during procedure qualification confirmed that weld joint had sufficient tensile strength and ductility after this PWHT.