Metallography of 9Cr steel power plant weld microstructures

摘要

The microstructural characterisation of welded joints subject to creep and the formation of the heat affected zone (HAZ) in tungsten alloyed high temperature 9% 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 are presented, together with the qualitative and quantitative results of metallographical investigations. 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 of the metallurgical investigations will be compared with the results obtained in actual welds.