| In modern production, mold with high quality, high efficiency, saving materialsand low cost characteristics, has been widely used in automotive, aerospace,manufacturing, household appliances and all walks of life. Hot-work die workingenvironment is particularly complex, often working in high temperature, highpressure and high stress conditions. Long-term service inevitably will producefailures, such as wear, fatigue and fracture failure, which affects the quality of theproducts, increases the cost, reduces the production efficiency, leading to enormouseconomic losses.This research designed and prepared a certain wear-resisting and anti-frictioncladding on the H13steel surface with the laser cladding technology. This claddingcan reduce the friction wear between the forming mold and work piece, aiming atimproving the performance and life of mold. At the same time, it can put forward thefeasibility report for the hot-work die fast repairment through remanufacturingdesign.This study prepared MoS2+SiC/HD-1(4Cr3Mo2Ni2Mn2VNbB) claddingmaterial on the45steel through the semiconductor laser. The microstructure andproperties are studied by means of OM, XRD, SEM, EDS, Microhardness tester,HT-1000high temperature friction and wear testing machine and other equipment.Studied the influence of the content of SiC and MoS2, scanning speed on the claddingforming, microstructure, the friction coefficient and volume wear rate under thecondition of room temperature and300℃. Through the orthogonal experimentdesign(three factors three levels), optimized the combination of coating formula andlaser scanning speed. At last, prepared6%SiC+4.5%MoS2/HD-1compositecladding on H13steel substrate, and discussed the feasibility for repairing andremanufacturing process of H13hot-work mold by laser cladding.Research shows that, from outside to in, the laser cladding layer tissue canobviously divided into cladding layer, the fusion zone and heat affected zone. Thefusion zone with a thin light band, presents the characteristics of planar crystals, andgradually shift into columnar crystals organizations. And then into the cladding region,it presents cellular crystals, gradually shift into branches and isometric crystals. Study found that, the hardness of pure bonding phase (HD-1) coating is about620HV0.2. The cladding hardness and abrasion resistance are obviously improvedwith SiC and MoS2particles. XRD showed that, the cladding existed no SiC andMoS2phase, but formed the supersaturated α-F and Fe-Ni-Cr alloy solid solution andFe7C3, CrSi2hard phase, which improved the hardness and wear resistance. SEMand EDS analysis found that there is a large number of uniform micro holes, wherethe Mn, Fe, S, Cr content is higher, which can form sulfides with lubrication toprotect the coating surface during the friction. With the increasing of scanning speed,the microstructure exhibits obviously grain refining. More SiC can make organizationshift to dendrites, and carbide number in the cladding layer increase, leading to thefurther improvement of the hardness to730HV0.2. With the content of MoS2increasing, the coating hardness decreased because of the role of the soft phase, but ithad no significant effect on the cladding organization and the grain size.Through the friction and wear performance analysis, we found that the influenceof scanning speed on friction coefficient and volume wear rate is not obvious. Theinfluence of SiC and MoS2content is more obvious. At room temperature, the higherthe SiC content, the smaller the volume wear rate and friction coefficient. They bothare the minimum value when the SiC content is9%. When the MoS2content is4.5%,the former is the minimum value. But the latter is smallest when the MoS2content is9%. At300℃, when SiC content is6%, volume wear rate and friction coefficient isthe smallest. The MoS2content is higher, the volume wear and friction coefficient issmaller. When the content is9%, they both are the smallest.Based on the analysis of single factor experiment and orthogonal experiment, theoptimal combination of laser cladding preparation is:6%SiC,4.5%MoS2and12mm/s scanning speed. The laser cladding layer on H13steel with this optimalcombination was prepared successfully: smooth surface, less crack and porositydefects, low dilution rate, good metallurgical combination between coating andmatrix, and small heat affected range.Compared with HD-1cladding and H13laser hardening layer, HD-1+6%SiC+4.5%MoS2cladding presents mild adhesive wear,abrasive wear and oxidationwear. At300℃high temperature,the laser cladding improved the wear resistancesharply. The volume wear rate is0.12x10-3mm3/m, respectively only1/3and1/4 of HD-1cladding and H13steel; the friction coefficient is about0.21, only60%ofthe H13steel laser hardening layer.H13hot-work die repairing and remanufacturing by laser cladding is feasible. |
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