EFFECT OF PHASE-TRANSFORMATIONS ON THE CREEP-RUPTURE PROPERTIES OF 2 TYPE-316 WELD METALS

Many of the factors which give rise to the low and variable creep rupture properties of type 316 weld metals are not yet fully understood. In the present study two weldments fabricated using the same welding parameters, but with compositional differences which give rise to different weight fractions of sigma phase and M23C6 carbides have been examined after creep testing. It was found that lower creep rupture strength and ductility was associated with higher weight fractions of sigma phase, which give rise to a higher number density of cavities at low deformation levels and facilitate crack propagation along sigma-austenite interfaces. The observed microstructural differences have been explained with reference to the predictions which can be made using thermodynamic analysis. © 1990 Chapman and Hall Ltd.