Microstructure and tribological performance of a steel based Surface Nano composite produced by friction stir processing.

This present investigation, was used to produce steel-Fe48Cr18Mo7Nb6C4B16Y1 surface nanocomposite on st14 steel substrate. The Nano structure particles was distribute into the st14 substrate by friction stir processing. High-quality composites were successfully produced with WC tool and tilt angle of 3°.A constant tool rotation rate of 400 rpm and travel speed of 100 mm/min was used. Microstructural analyses showed a uniform distribution of reinforcement particles inside the nugget zone. Microstructure and mechanical properties of samples were investigated by optical microscopy (OM), scanning electron microscopy (SEM), macro-hardness and wear measurements. The smaller grain sizes of the ferrite and reinforcement phase caused increase in hardness and wear resistance within the stir zone. The surface nanocomposites also exhibited lower friction coefficient and wear rate. It was found that the addition of nano structure particles to the st14 matrix alloy affect the mechanism of wear. The results reveals that both the extent of wear and the wear rate are significantly lower in the surfaceNano-composite layer as compared to FSPed matrix and the as-received substrate