Redesign of Exhaust Systems for Naval Gas Turbines: Usage of a New Cr-Mn Austenitic Stainless Steel

Studies performed earlier show that the thermal shock loading has influence, together with the normal service loadings, in the fatigue life of some critical welded joints present in the exhaust systems of naval gas turbines [1-2]. In order to prevent the fatigue crack propagation that was verified in service [3], a recently developed ultrahigh-strength austenitic stainless steel was selected (Cr-Mn steel - number 1.4376) and its mechanical properties and the fatigue resistance are under study. This new material could replace, locally, the current material used in the main structure of the exhaust system (AISI 316L). Experimental data are shown. The temperature measured at the critical locations was about 350°C and the pressure applied in the system was calculated through a Computational Fluid Dynamics simulation (CFD), whose results are presented in the paper. The stresses induced by the loadings will be important to estimate the lifetime from the fatigue resistance tests (S-N curves) that will be performed, at 350°C, in butt and T-welded joints of AISI 316L stainless steel with Cr-Mn austenitic stainless steel.