STRESS MEASUREMENT IN ALUMINA SCALES ON HIGH-TEMPERATURE ALLOYS USINGX-RAY STRESS EVALUATION AND LASER RAMAN-SPECTROSCOPY

The effect of silicon and titanium on the spallation resistance of alu mina scales grown on NiCrAlY-type alloys has been investigated using m odel alloys with different additions of Si or Ti. For this purpose cyc lic oxidation experiments have been carried out at temperatures betwee n 950 and 1100 degrees C. After various times stresses in selected Si- doped samples have been determined by Xray stress evaluation (XSE) at ambient temperature. The compressive stresses in the scales have been found to increase with an increasing oxidation time tending to become constant for long times. The development of stress is affected by the presence of Si. Laser Raman spectroscopy (LRS) has been calibrated for strain measurement using XSE results. Then LRS has been applied for s train measurement at higher temperatures.