AlN formation and enhancement of high-temperature oxidation resistance by plasma-based ion implantation

Nitrogen ion implantation by plasma-based ion implantation (PBII) with a negative pulse voltage of 10 kV amplitude led to formation of AlN layer on an aluminum casting alloy (Al–7Si). The structural analysis by super-glancing-angle X-ray diffraction using synchrotron radiation indicated that the crystalline AlN phase was formed in the nitrogen-ion-implanted AlN layer. The AlN layer on the sample surface prevented oxygen from penetrating into the sample matrix at the temperature of 500 °C, suggesting the enhancement of oxidation resistance by PBII nitrogen ion implantation. The remarkable enhancement of oxidation resistance was ascribed to the production of AlN layer with no microscopic defect such as pinhole.