Microwave synthesized composite claddings with enhanced cavitation erosion resistance

Abstract

In the current work we developed Ni-SiC based composite claddings on SS316L through microwave irradiation using different reinforcement weight fractions and particle sizes (micron to nano scale). A bimodal derivative using equal proportions of both micro and nano scale particles was also developed. Microstructural characterization showed claddings were composed of columnar structure with precipitated intermetallic phases segregated at the grain boundaries. The Ni-SiC bimodal particle reinforced claddings showed highest hardness and fracture toughness. All the developed claddings showed significantly high cavitation erosion resistance compared to SS316L steel. The Ni-10 wt% SiC bimodal particle reinforcement cladding showed highest erosion resistance with around 5 times lower erosion rates than SS316L steel along with highest incubation period. The investigated bimodal particle reinforced cladding also outperformed the thermal sprayed WC10Co4Cr and Stellite 6 coatings and CA6NM hydroturbine steel used for comparison. Detailed structure-property correlation analysis showed that the exquisite performance of the investigated bimodal particle reinforcement cladding can be ascertained to high hardness and H/E ratio (inversely related with plasticity index). Compared to brittle failure mode exhibited by thermal spray coatings due to splat delamination, the Ni-SiC claddings showed mixed signatures of both ductile and brittle failure modes. Examination of the eroded surfaces of the claddings showed presence of significant number of micro pits surrounded by extruded lips and dislodged intracellular phase. Detailed SEM analysis of the samples near incubation period showed damage accumulation initiated around these intermetallic phases in the form of cracks and pits. It was shown that Ni-SiC based microwave-derived bimodal particle reinforced claddings are an effective and efficient solution for countering the cavitation induced erosion in fluid machinery