As part of the APT project on protection from tungsten release from the APT spallation target during postulated accident conditions, the use of Inconel 718 as possible cladding material for tungsten targets was considered.The experiments were conducted at high temperatures to evaluate the rate of oxidation of Inconel 718 over as wide a temperature range as possible, as well as to determine the high-temperature failure limit of the material.Samples of Inconel 718 were inserted into a preheated furnace and oxidized in air for varying periods of time.After cooling, the samples were re-weighed to determine their weight gain due to the uptake of oxygen.Three oxidation regimes were determined for Inconel 718: a low-temperature regime in which the samples became passivated after the initial oxidation, intermediate-temperature regime in which the rate of oxidation was limited by diffusion and exhibited a constant parabolic rate dependence, and a high-temperature regime in which material deformation and damage accompanied an accelerated oxidation rate above the parabolic regime.At temperature <1173 K, the rate of oxidation of the Inconel 718 surface was found to decrease markedly with time; the parabolic oxidation rate coefficient was not a constant but decreased with time.This was taken to indicate that the oxide film on the surface was having a passivating effect on oxygen transport thought the oxide to the underlying metal.For temperatures in the range 1173-1573 K, the time-dependent rate of oxidation as determined once again by weight-gain measurements was found to display the classical parabolic rate behavior, indicating that the rate of transport of reactants through the oxide was controlled by diffusion through the growing oxide layer.Parabolic rate coefficients were determined by least-squares anal. of time-dependent mass-gain data at 1173 K, 1373 K, 1373 K, 1473 K, and 1573 K.At temperatures >1540 K, post test examination of the oxidized samples revealed that the Inconel 718 began to lose strength and to deform.At 1540 K, samples which were suspended from their ends during testing began to demonstrate axial curvature as they lost strength and bowed under their own weightAs the temperatures of the tests were increased, rivulets were seen to appear on the surfaces of the test specimens; damage became severe at 1560 K.Although melting was never observed in any of these tests even up to 1620 K, it was concluded that the Inconel 718 clad should not be expected to protect the underlying tungsten at temperature >1540 K.