Correlation between platinum-aluminide coating features and tensile behavior of nickel-based superalloy Rene®80

The effect of platinum (a rare metal)-aluminide coating parameters on the tensile properties of nickel-based superalloy Rene (R) 80 was evaluated at 871 degrees C. For this purpose, initial layers of platinum with different thicknesses (2, 4, 6 and 8 mu m) were coated on tensile samples. Then, low-temperature high-activity (LTHA) and high-temperature low-activity (HTLA) processes were used for aluminizing. Results of microstructural evaluations using scanning electron microscope (SEM) and phase analysis by X-ray diffraction (XRD) showed a three-layer structure coating for different platinum layer thicknesses and both aluminizing processes. Increasing the thickness of the platinum layer from 2 to 8 mu m led to the improvement in the final coating thickness from 91.6 to 102.1 mu m in HTLA. This increase was from 128.1 to 148.6 mu m in LTHA. The results of hot tensile tests at 871 degrees C showed a decrease in strength properties of the coated samples compared to the uncoated ones. However, HTLA and high thicknesses of the initial platinum layer showed an intense reduction. The results of fractographic evaluations about uncoated samples showed a ductile fracture. On the other hand, coated samples showed a simultaneous ductile and brittle fracture failure mechanism. But the main fracture morphology was brittle cleavage fracture which was for the HTLA.