The effect of low-energy nitrogen ion implantation on surface hardening and high-temperature oxidation of niobium-molybdenum alloys

This study developed modes of surface modification of a niobium-molybdenum alloy by nitrogen ion implantation to investigate the effect of treatment on the alloy's protective properties during high-temperature oxidation. The chemical and phase composition of the modified surfaces was analyzed by X-ray spectral microanalysis and X-ray diffraction. The thickness of the implanted layer was determined by transmission electron microscopy. The results of the modulus of elasticity, microhardness, and nanohardness measurements of the alloy samples in their initial and nitrogen-implanted states are presented. The implanted and initial alloys were evaluated for resistance to high-temperature oxidation in air for 15, 30, and 60 minutes at a temperature of 900°C. The surface structure was examined, and the thickness of the oxide layer was determined after high-temperature oxidation tests using scanning electron microscopy. The specific weight gain of the samples was measured during the testing process. The results show that, in the ion implantation modes used, nitrogen concentrations of up to 39.3 at% are achieved at a depth of approximately 100 nm in the surface layer, with the formation of niobium nitrides. Moreover, the treatment enhances the alloy's mechanical properties, including an increase in the modulus of elasticity, microhardness, and nanohardness as well as improve the alloy's resistance to high-temperature oxidation, as evidenced by the formation of thinner oxide layers and a lower weight gain compared to the untreated alloy.