Effect of thermal cyclic corrosion on the microstructural degradation of platinum aluminide coatings

Abstract

The increase in fuel prices and environmental pollution has urged the need for more efficient and environment-friendly paths to operating gas turbines. One way to tackle this is by increasing the inlet temperature in the turbines. The present study is to understand the effect of thermal cycling on the microstructural degradation of Pt-Al coating on CM247 LC substrate. Pt-Al coated samples are subjected to 1000 °C for 480 cycles. Each cycle consists of 55 min of heat exposure and 5 min of cooling. The cross-section of each sample is subjected to image analysis to understand the compositional variation under cyclic conditions. The β-NiAl and RE concentration show a decreasing trend with an increase in the number of cycles, whereas γ’-Ni3Al and porosity concentration show an increasing trend with an increase in the number of cycles. 60–70 vol. % γ’-Ni3Al concentration must be present to affect adversely the coating degradation significantly.