Laser Surface Hardening Of Mower Blade

Wear is one of the main failure modes of agricultural machinery parts. Based on the anti-wear requirements for the mower blades, the laser surface hardening method was used to improve the blade wear resistance, which is of practical significance and application value to the anti-wear research of the agricultura1 machinery parts.In this paper, we investigated out two kinds of laser surface strengthening methods, including the laser surface strengthening and the laser cladding to harden the surface of alloy, on the HRc42-47 65Mn blades and the specimen which were processed by the tempering and quenching method with temper troostite of the original microstructure. The laser hardening treatment was carried out with the IS-5000QB laser, and the orthogonal test was used to investigate influences of laser surface hardening process parameters on the hardened layer, the microstructure and the mechanical properties of the cladding layer microstructure. Simultaneously, optical microscopy (OM), scanning electron microscopy (SEM) and other methods were used to study the organizational structures, the surface morphology, and the composition of laser cladding alloy hardened layer. Moreover, we studied the wear resistance using a micro hardness meter and an MMS-2A friction and wear meter.Orthogonal experimental results showed that the power level and the laser scanning speed are the significant impact factors on the hardened layer microstructure and properties, and the power level and adjacent track pitch are the significant impact factors on the cladding layer microstructure and properties. Hardened by the IS-5000QB laser, the best combinations of laser hardening parameters are:power level 130W, scanning speed 240mm/min, the adjacent track pitch 0.5mm. The surface microstructure is hidden needle martensite and the hardness is HV 756 when the blades are laser-hardened.For surface hardening of laser cladding alloy hardened layer, Nickel-based alloy 50%Ni35B powder was used as the matrix, at the same time the TC and WC powder were the hardening phase. When Ni35B powder was constant, with the optimized combination of laser parameters:power level 320 W. the scanning speed 220mm/min, the adjacent track pitch 0.6mm, Ni-based alloy powder having a different ratio of TiC and WC were cladding and the influence on the generated cladding organizational performance due to the composition changes was explored. With the decrease of WC, TiC content, the hard phase reduced, reducing the heterogeneous nucleation rate and hardness value of the cladding layer. However, it would increase the toughness of the cladding layer, reduce the micro cracks in the cladding layer, and improve the quality of cladding. The screened preferred composition of cladding alloy powder is 50%(Ni35B)、30%TiC、20%WC. The mower blades with the optimized composition and processing parameters of laser processing will have better overall performance and the obvious change in the cladding layer, the transition and the matrix organization on the cross-sectional sample cladding can be seen, and at the same time, the micro hardness also exhibits a good transition from big to small, steel and the metallurgical bonding with the substrate steel 65 is formed.After actual mowing test, compared with the 65Mn steel mower blades, the laser cladding blade’s life is longer and has better environmental adaptability. The laser cladding alloy hardened blade is particularly better.