TWI Industrial Member Report Summary 375/1988
By R N Gunn
High alloy stainless steels are finding increasing use in extreme corrosion environments, where other stainless steels are attacked and the Ni-based alloys are too expensive. However, on welding autogenously, segregation in the weld metal causes reduction in pitting resistance in chloride media. The present programme investigated the use of friction welding for a number of stainless steels, both austenitic and duplex, covering the composition range of 18-25%Cr, 7-27%Ni, 0-6.5%Mo, and up to 0.2%N.
Friction welds were produced in commercial 50mm OD X 6mm wall pipe with TIG welds for comparison, the latter being made autogenously and with overalloyed fillers. Pitting resistance was determined potentiodynamically in synthetic seawater at 50ºC and by weight loss experiments in ferric chloride solution; metallographic examination and microanalysis were also carried out.