High-temperature durability of steel and welded joints in exhaust gas environment

Abstract

This study analysed the causes of the varying durability of two shields of inert gas generator burners. Material tests were carried out: chemical analysis, metallographic evaluation and microanalysis of surface layers. These tests showed that the shield that was destroyed after approx. 40 h of the generator's operation was made of non-alloyed steel, whereas the shield which worked for over 6 months and burned through in the area of the welded joint was made of austenitic steel. It was found that the sulphur concentration in the burnt-through area was higher than outside, which suggests easier penetration of sulphur into the weld. In order to increase the high-temperature corrosion resistance by adding sulphur compounds, it is advisable to verify the selection of steel type, e.g. by using heat-resistant austenitic steel with sulphur-binding rare earth metals, creating thin layers with good adherence to the steel surface.