Characterisation of pipe welds and HAZ in primary heat transport system piping of pressurised heavy water reactors

Abstract

Weld joints of SA 333 Gr. 6 steel pipe have been prepared using GTAW root pass and SMAW filling of V-groove according to welding procedure specifications (WPS) conforming to ASME Sec IX, a procedure commonly used to fabricate nuclear piping system components. The objective of the present study was to characterise the base metal, weld deposit and HAZ of the pipe weld in terms of their chemical composition and metallurgical, mechanical and fracture mechanics properties. The fracture toughness behaviour of the welds and HAZ has been characterised by J-integral parameters. The fatigue crack growth rate has been characterised by Paris Law. The stretched zone width (SZW) at the fracture surface has been measured with SEM to evaluate the initiation fracture toughness. The values of initiation fracture toughness estimated on the basis of SZW and blunting line from EGF recommendation have been compared. The fracture mechanics properties of the base metal, weld and HAZ have been compared and correlated. Fracture mechanics properties of the weld and HAZ have also been correlated with microstructure.