The use of Light and Electron-microscopic Investigations to Characterise the Creep Behaviour of Welded Joints in Modern Power Station Materials

摘要

The micro structural characterisation of welded joints subject to creep and the formation of the heat affected zone (HAZ) in tungsten alloyed high temperature 9 - 12% chromium steels is extremely important in modern power station construction. In these investigations, creep specimens were made available taken from fabrication welds in steel castings. The results of the hardness measurements carried out, together with the qualitative and quantitative results of metallographical investigations are presented. Special attention is paid to softening in the HAZ and the effect which this has on the creep resistance and fracture behaviour of welded joints. TEM investigations with the aid of energy filtering (EFTEM) were used to clarify the mechanisms taking place. The results obtained from tests on actual welds confirm the information gained from the basic trials carried out.