Liquid phase surface nitriding of aluminium using TIG process

Liquid phase surface nitriding of AA5052 aluminium was performed using the heat of a TIG (tungsten inert gas) torch in a gas shielding which was a mixture of argon and nitrogen. The feasibility of obtaining nitride compounds at various TIG processing parameters and nitrogen contents in the shielding gas were studied. The presence of AlN phase was proved by X-ray diffraction analysis. Scanning electron microscopy with EDS analyser was carried out to study the morphology and chemical composition of the nitride phase. The microhardness test was also performed on cross sections of treated layers. This measurement demonstrated that the surface hardness of the untreated aluminium was increased from 52 HV for the untreated aluminium alloy to as high as 1411 HV for the nitrided sample. It was also noticed that liquid phase surface nitriding reduced the wear rate to less than quarter of that of the untreated substrate.