TWI

In relation to the application of ferritic/martensitic steels as cladding and duct materials in advanced nuclear reactors, an investigation is presented into the friction stir welding of P91 high alloy steel (0.11%C, 0.45%Mn, 8.41%Cr, 0.96%Mo) plates (thickness 6.5 mm), optimisation of tool materials and process parameters, and examination of welded joint microstructure and mechanical properties. The tool materials studied were a W-Re alloy and a composite tool consisting of cubic BN particles embedded in a W-Re matrix, incorporating a Tri-flute probe with flat scroll shoulder geometry or a stepped spiral probe with convex scroll shoulder geometry, respectively. Tool wear was assessed by shadowgraph measurements. Bead on plate and butt welding experiments were undertaken to optimise tool design and process parameters such as rotational speed, travel speed and plunge depth. Weldment microstructure was observed by SEM and energy dispersive X-ray spectroscopy. Mechanical properties were characterised by tensile tests and microhardness measurements.

9th International Symposium, 15-17 May 2012, Session 10A: FSW Steel, Paper 03