ANALYSIS OF HP2 NOZZLE ASSEMBLY FAILURE OF A GAS TURBINE

摘要

The HP2 nozzle assembly of one of the process platform failed by plastic deformation of the vanes after an operating life of 20,000 hours. The vanes were made of alloy 31. The failed vanes were subjected to detailed failure analysis by conducting metallography, hardness testing, energy dispersive spectroscopy, x-ray diffraction and electron probe micro analysis. The phenomenon of sulphidation and catastrophic oxidation was not observed in the material. It was found that the material had undergone high temperature oxidation. The material did not show any signs of creep damage and phase growth .Preferential attack of carbides was identified. The alloy exhibited loss of hardness at the aerofoil surface which aided material erosion and degradation of alloy strength properties. Various thermal barrier coatings to prevent high temperature oxidation were studied.