Influence of high heating rates on evolution of oxides on directed laser energy additively fabricated IN718

Abstract

The effect of non-isothermal treatment in oxygen-containing air, via heating rates of 10, 50, and 1000 °C/min until 1000 °C followed by furnace cooling to room temperature on oxides formed on directed laser energy additively fabricated IN718 was studied. Another set of samples heated up to 1000 °C using the same heating rates were isothermally held at 1000 °C for 1 hr followed by furnace cooling to room temperature. X-ray photoelectron spectroscopy indicated the presence of NiO on samples only heated at 1000 °C/min. Also, results indicated the absence of Fe-oxides on non-isothermally treated samples, irrespective of heating rate. However, isothermal treatment confirmed the presence of NiO on all samples and Fe-oxides on samples heated via 50 and 1000 °C/min. The durations in complement with the kinetics of the thermal treatments influenced oxide evolution in the samples. Such an experimental approach was adopted to study the material response under dynamic short duration-high temperature oxidation.