| As one of the most frequently used steel in mold industry, H13steel (4Cr5MoSiV1) is widely used in large impact load forging dies, hot extrusion die, forging die, die mold etc. In actual working conditions, the normally high temperature wear and thermal fatigue failure, seriously reducing the life of the product often effected by the molds repeatedly by the alternation of high and low temperature. According to the statistics, most of the mold failure was concentrated its surface. Therefore, the optimization of mold design, mold-making material selection and improve the performance of the mold surface will become the mold workers’highly valued and committed to addressing the key issues. In recent years, by means of surface modification, especially laser cladding technology to increase the life of the mold has obtained more satisfactory results. The reported has been said that the selective laser cladding composite coating on the surface of H13steel, especially the super alloys reinforced phase contained composite coating is still uncommon involved. In view of this, we use of selective laser cladding technology in preparation cladding coating of single-channel Ni-Al intermetallic compounds on H13steel surface, analyses the effect of the intermetallic compound coating surface fusion quality, the coating microstructure morphology, phase composition and coating mechanical properties by A1content in the mixed powder, in order to improve the overall performance on the surface of H13hot die steel, to provide the theoretical basis and an effective way to extending the life of mold.This paper briefly summarizes the different laser processing parameters on the macroscopic quality of coating; analyzed the same composition of different process parameters on the morphology of the coating microstructure and the different components of different microstructure appearance by optical microscopy (OM); With X-ray diffraction (XRD) ratio obtained under different components coating material phase qualitative analysis; Along the cross-section of each coating layer depth direction, the microhardness were characterized by microhardness; The coatings were characterized by thermal fatigue properties of high temperature wear properties of the coating and thermal shock.The X-ray diffraction pattern fully described the coating matrix phase stable austenite phase y-Ni and (Ni, Cr)solid solution, the main intermetallic compounds is Ni3Fe when there’s no Al in the coating. Addition of Al, the Ni-based coating mainly tend to occur with Al reaction self-propagating super alloys strengthening phase y’-Ni3Al, β-NiAl phase generated by Ni and Al self-propagating reaction when the Al content is too high, with the Al content increases, the cladding coating (Fe, Cr) solid solution content has also been increased. And compared to the trend of the NiAl coating with5%Mo was more slowed.The coating microhardness test results show that the microhardness of the coating compared to the substrate have a larger degree of improvement, and the coating with5%Mo compared to the coating without Mo the microhardness is higher, the highest microhardness up to5.50times the size of H13steel (267HV). And after the addition of Al in the binding interface microhardness steep drop and pick-up in the heat-affected zone (HAZ).The results of the high temperature wear and the first macroscopic cracks under650℃test show that fluctuations in friction coefficient and wear mass loss of H13steel is worse than the coatings, and the coating with Mo contained get a better mechanical property than the coating without Mo. And, the first macroscopic crack of the coatings late than H13steel and because of the solid solution strengthening and grain refinement role by Mo, the first macroscopic crack was found later than the coating with out Mo. The macrostructure quality of the coating will impact the results of experiment, the poor macrostructure quality will cause the first macroscopic crack too early. |
PDF Full Text Request