Fe-Cr-C-V plasma surfacing layer improving wear resistance and impact toughness of rotary blade

Abstract: In order to solve the problems of poor wear resistance and frequent failure of agricultural machinery contact soil components, Fe-Cr-C-V plasma surfacing layer was prepared on 65Mn steel matrix by plasma surfacing welding technology. Microstructure and phase composition of surfacing layer were analyzed by means of metallographic microscope and X-ray diffraction. Microhardness, wear resistance and impact toughness of surfacing layer were analyzed by means of microhardness tester, reciprocating friction and wear tester, self-made soil-bin wear tester and impact testing machine. The results showed that the cross-section of the surfacing welding specimen showed surfacing region, bonding region and substrate region, the substrate and coating diffused with each other, showing good metallurgical bonding, the coating dilution rate was low, and there were no defects such as porosity and slag inclusion. Fe-Cr-C-V series surfacing layer was mainly composed of α-Fe,Cr7C3,M7C3(Fe,Cr7C3), Fe-Cr solid solution, VC, etc. The microstructure and hard phase morphology of Fe-Cr-C-V surfacing layer were improved. In addition to the original coniferous and hexagonal primary carbides, the dispersed spherical carbides, columnar crystals also appeared. Composed with 65Mn hardened steel, the Vickers hardness of Fe-Cr-C-V series alloy layer was improved by 75% and the wear quality was reduced by about 67%. Compared with Fe-Cr-C series alloy, Fe-Cr-C-V series alloy had finer microstructure, higher hardness, lower wear and better impact toughness. Fe-Cr-C-V surfacing layer had smaller wear quality, more stable wear curve and better wear resistance, this is because that the carbide hard phase dispersed on 65Mn matrix play the role of anti-wear skeleton, while the toughness phase in Fe matrix bonds and solidified the carbide, and the 2 interactions jointly improved the wear resistance of the coating. The refinement and dispersion of hard phase and the appearance of new VC phase were the main reasons for the coating strengthening, while the carbide morphology improved the impact toughness of the coating. The average hardness and impact toughness of Fe-Cr-C alloy were HV0.5710 and 6.2 J/cm2 respectively. The average hardness of Fe-Cr-C-V series alloy layer was HV0.5810, and the impact toughness was 7.5 J/cm2. Fe-Cr-C-V series alloy layer had better wear resistance and impact toughness. Compared with the commonly used 65Mn subsoiler tip, the wear quality of subsoiler tip with surfacing layer was reduced by 78%. Field experiments showed that the average wear quality of the rotary blade with surfacing layer was reduced by about 50% compared with the conventional 60Si2Mn rotary blade without surfacing layer. For the rotary blades without Fe-Cr-C-V surfacing layer, there were obvious wear marks in the intersection area between the cutting edge and the side cutting edge, and the blade passivation was serious, while the surfacing layer on the blade of the rotary blade with surfacing layer remained relatively intact, without serious wear and coating peeling. The average wear quality of rotary blade with surfacing layer was 32 g, and that of ordinary rotary blade without surfacing layer was 60 g. The hardness phase of Fe-Cr-C-V coating studied was uniformly distributed and there was no obvious hardness gradient, which has important reference value for extending the life of soil contact parts of agricultural machinery. In addition, plasma surfacing welding technology was used to prepare Fe-Cr-C-V series wear-resisting coating on the surface of the soil contact parts of agricultural machinery, which has low cost, high efficiency, flexible and convenient technology and high application and promotion value. Compared with the commonly used rotary blades with 65Mn and 60Si2Mn materials, the rotary blades with Fe-Cr-C-V surfacing layer has good wear resistance and excellent comprehensive mechanical properties.