Parametric optimization of friction stir process for developing high strength and wear-resistant chromium reinforced NiAl bronze composite

Abstract

Abstract The present study focuses on fabricating a chromium-reinforced nickel aluminium bronze (NAB) composite using an optimized multi-pass friction stir processing (FSP) technique. The tool rotation, tool traverse speed, and volumetric concentration of the reinforcement were taken as input process parameters, whereas the ultimate tensile strength (UTS), yield strength (YS), percentage elongation (% E), microhardness, and sliding wear rate were taken as output responses. Taguchi-Grey relational analysis (GRA) was utilized for optimizing the input process parameters, which were 1000 r.p.m., 28 mm min−1 and 15.7%, respectively. The most significant parameter was traverse speed, followed by tool rotation and volumetric concentration of the reinforcement. FE-SEM, EDS, and XRD analyses were performed to characterize the as-cast NAB, chromium powder, and FS-processed composite. The tensile strength and wear resistance of the processed composite are enhanced compared to the base NAB alloy on account of significant grain refinement due to the stirring action of the tool pin in the processed zone and the dispersion of chromium reinforcement. The wear rate of the composite was reduced as the tool rotation, traverse speed, and Cr particle volume concentration were increased. The maximum UTS of the prepared composite was 701 MPa, whereas the UTS of the as-cast NAB was 620 MPa. It was observed that as-cast NAB exhibited a hardness value of 286 HV, which was improved to 385 in the FSPed prepared composite. It was found that as-cast NAB exhibited 7.0 × 10–6 gm m−1 of wear rate, whereas the FSPed composite showed a minimum wear rate of 5.5 × 10–6 gm m−1. The microstructural examination revealed that the wear mechanism in the case of as-cast NAB was primarily adhesion, whereas the abrasion was found to be the governing mechanism of material removal in the processed composite.