Surface Modifications of Low Carbon Steel Using Friction Stir Processing

Abstract

Surface modification was carried out on low carbon steel sheet (JISG3141 SPCC) using Friction Stir Processing (FSP). The friction stir processing slightly increased the surface hardness of the low carbon steel sheet. In order to significantly increase the surface hardness of the low carbon sheet, WC powder having a size of 5 μm was embedded into the low carbon surface layer using sandwich method where a carbon steel cover is applied on the WC powder present in the groove of 1.5 mm depth ant 3 mm width in the carbon steel sheet and the friction stir processing was applied to the sandwich using WC-Co tools. The cover was applied to prevent the loss of WC particles during processing. SEM and TEM observation showed that the number of passes and the reversing of the direction of rotation in the next passes significantly affected the homogeneity and the distribution of the WC powder in the matrix. Moreover, crushing of WC powder to smaller ones was observed. WC fraction area analysis revealed the high density of WC distribution in the matrix. The hardness distribution showed that the surface modified hardness increased to about 700 HV at the mid depth of the surface modified sheet using WC powder compared with 400 and 500 HV at the deeper and shallower levels of depth respectively.