Material degradation of dissimilar metal welds subjected to long-term ageing

Abstract

The objective of this study was to investigate the material degradation of dissimilar metal welds for reactor-pressurised vessels in the primary system of nuclear power plants. The influences of long-term ageing of dissimilar metal welds on microstructural and mechanical characteristics were studied. The long-term ageing tests were interrupted at various stages to obtain different levels of degraded specimen. The microstructural changes in the base metals and weld metals were evaluated by optical and electron microscopy with respect to twins, grains, precipitates and phase transformations. The residual stress and mechanical softening were also discussed in terms of microstructural changes during long-term ageing.

Keywords:

• Dissimilar metal
• Ageing
• Degradation
• Microstructure