Basic Aspects of the Weldability of 9-10% Cr-Steels for Advanced Power Generation

Abstract

There are strong environmental and economic demands to increase the thermal efficiency of fossil fuel-fired power stations, and this has led to a steady increase in steam temperatures and pressures resulting in worldwide plans for ultra-supercritical power plants. Modern life martensitic 9-10% Cr-steels are used widely to fu lfil the requirements resulting from the design aspects.

Basic investigations on the weldability of modern 9-10% Cr creep resistant steels which are presently in use and planned to fulfill this requirement were performed on pipes P91, E911 and a W-containing cast steel G-X 12 CrMo WVNbN 10 1 1. Gleeble simulation representing the manual metal arc welding process were applied to produce HAZ-simulated microstructures. After different post weld heat treatments they were tested using hardness tests, metallographic investigations, constant strain rate tests, creep and toughness tests. Main attention was given to the softening effect in the HAZ and its influence on the creep resistance of the welded material. This decrease shown by simulated and manufacturing welded samples seems to be less pronounced of the W-modified versions than observed at P91 material.