Mechanical properties and tribological performance of A356/Cr3C2-NiCr surface composite developed by high-velocity oxy-fuel and post friction stir processing treatment

Abstract

High-velocity oxy-fuel thermal spraying and post friction stir processing (FSP) techniques were utilized to fabricate a new lightweight metal matrix composite for industrial application in which A356 aluminum (Al) cast alloy and Cr3C2-NiCr were the matrix and reinforcements, respectively. The microstructure of the BM, friction stir processed samples, and composites were evaluated using optical microscopy and scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy. The investigations demonstrated that the coarse eutectic silicon blades were crushed to fine particles after FSP and the Cr3C2-NiCr coating were uniformly dispersed into the base metal (BM). The hardness of the samples was measured via microhardness and nanoindentation tests, which indicated a significant improvement (about twice the BM) in the hardness of the 4-pass friction stir processed composite. Considering the results of the uniaxial tensile test, the FSP enhanced the yield strength (YS) and ultimate tensile strength (UTS) of the samples. The YS and UTS of the 4-pass friction stir processed composite were nearly 53 and 22% higher than those of the BM, respectively. To study the tribological performance of the samples, the dry sliding wear test was conducted on the samples using a reciprocal wear machine. The results showed that the wear and friction performances of the composites improved dramatically (∼98% and 61% decrease in the wear rate and friction coefficient, respectively). Finally, the SEM investigations from the fracture surfaces, worn surfaces, and debris resulting from the wear tests were conducted on the samples to understand the fracture and wear mechanisms.