Research On Friction And Wear Behavior Between Coated Ultra-high Strength Steel And Hot Stamping Dieface

With the increasing demand for vehicle light-weighting and safe crash standards,hot stamping forming technology has become an ideal process for producing ultra-high strength steel parts.Since the hot stamping die is used in the working environment of periodic thermal and mechanical load,it is easy to accelerate the wear and failure of the dieface,thereby affecting the forming quality of the products.Therefore,it is necessary to understand systematically the tribological relationship between the dieface of hot stamping and the ultra-high strength steel,to reduce or suppress the wear of the hot stamping die.In this paper,the friction test device was developed to explore the friction and wear behavior of the dieface under hot stamping condition.And the laser cladding layer was prepared to reduce the wear of the dieface.The main research work is as follows:(1)The differential temperature friction test device was designed and built based on pindisk test method.And the device can simulate hot stamping forming conditions,that is,realize the differential temperature distribution environment between steel and dieface.Based on the hot stamping working conditions and the requirements of the pin-disk friction test,the heating system,cooling system,loading system,reciprocating motion platform,high temperature chamber,and friction coefficient measurement methods of the differential temperature friction test device were carried out.At the same time,COMSOL software was used to simulate and analyze the temperature field of the pin-disk contact interface in the device.So as to ensure that the friction contact temperature of the pin-disk is similar to the temperature in the actual hot stamping process during the test.(2)Based on the differential temperature friction test device,the differential temperature friction and wear behavior between coated ultra-high strength steel and dieface was studied.And the differential temperature friction test between coated ultra-high strength steel(Al-Si and GA coating)and the die steel H13 was carried out.By the change of friction coefficient,surface roughness,surface compound,wear surface and cross section morphology under the parameters.The changes of wear mechanism between coated ultra-high strength steel and dieface of die steel H13 after different friction time was explored.And the tribological behavior of the contact interface between dieface and sheet in hot stamping process was revealed.(3)The laser cladding technology was used to fabricate reinforced coating on hot stamping dieface,and the feasibility of laser cladding was verified.The pin-disk high temperature friction tests between the coated ultra-high strength steel(Al-Si,GA,GI)and Co based laser cladding layer were carried out at 700℃.The change of friction coefficients,wear rates,wear surface and cross-sectional morphology of Co-based coating against four kinds of coated ultra-high strength steels was analyzed.The results show that the wear resistance of the dieface after laser cladding is significantly improved,which provides certain engineering guidance for the improvement of the hot stamping die wear control.