Study On Laser Cladding Composite Coating And Wear Resistance Of H13 Die Steel

H13 steel is the most widely used and representative hot-working die steel,but because of the bad working and using environment,its surface is often invalidated due to thermal attrition and thermal fatigue,and thus its life is generally short.At present,laser cladding technology is widely used in surface strengthening and repairing of the molds.The cladding laser made by this technology is of good quality,with resistance of attrition,corrosion,heat and oxidation.In the selection of powder materials for laser cladding,NiCr-Cr₃C₂ composite powder is a good choice.It is composed of NiCr alloy powder and Cr₃C₂ ceramic powder,which has not only good resistance of high temperature and corrosion as NiCr alloy does,but also high hardness and strong oxidation resistance as Cr₃C₂ ceramic does at high temperature.In this paper,the composite coating of H13 and Cr₃C₂ NiCr powder is prepared on the surface of H13 matrix by laser cladding technology.By means of scanning electron microscope?SEM?,energy spectrometer?EDS?and X-ray diffraction?XRD?,characteristics of the microstructure and phase structure of the cladding powder and the coating together with combination of coating and matrix are observed and analyzed.The thermal fatigue performance of the cladding layer was tested by thermal shock test;the microhardness of the surface and cross section of the coating was measured by micro-hardness tester;and the influence of various factors on the attrition resistance of the matrix and cladding layer was tested by high temperature friction and wear tester,the attrition resistance of the two was compared.Based on the experimental data,combined with numerical simulation and mathematical statistics,a high temperature friction and wear model based on quadratic regression orthogonal was established and the theoretical service life of the die was predicted.The composite coating of 85%H13+15%NiCr-Cr₃C₂ composite powder prepared by laser cladding under certain process parameters has the best cladding quality.The composite powder presents the Fe-Ni and Fe-Cr phases in the XRD pattern.The main phases of the cladding layer are martensite,Cr₃C₂,Cr₇C₃ and carbide?Cr·Fe?₇C₃,among which the most obvious diffraction peak is martensite,which shows that the transformation of martensite in the microstructure after cladding is relatively complete.After laser cladding treatment,the microhardness of the cladding layer increased significantly.With the increase of Cr₃C₂-NiCr content,the microhardness of the cladding layer also increased.The surface microhardness of the cladding layer is close to 1100HV0.2,which is about 2 times of the Matrix?570HV0.2?,and the average microhardness of the cladding layer?920HV0.2?is about 350 HV0.2 higher than that of the Matrix,which realizes the aim of strengthening the surface of H13 steel.Under the same conditions,the attrition depth of the matrix is significantly larger than that of the cladding layer.The influence of load and temperature on the attrition depth of the matrix is significant,while the influence of load and temperature on the attrition depth of the cladding layer is highly significant.Combined with the contact conditions of die and blank derived from the numerical simulation of hot reverse extrusion forming,the attrition depth of each node in single forming was calculated by numerical integration,and the attrition maximum was 0.5 mm depth,the theoretical service life of the dies and dies with laser cladding are predicted to be 5240 pieces and 6636 pieces respectively.