Research On The Boronizing Process Of H13 Die Steel And The Structure And Properties Of The Layered Layer

Pack boriding is an effective means to improve the performance and service life of H13 die steel.But the traditional pack boriding has the disadvantages of high temperature and long holding time.Pretreatment of surface deformation,catalysis of rare earth and pack boriding agent used at low temperature has become a research hotspot.In this paper,the experiments of ordinary boronizing,Ni-boronizing,catalysis of rare earth and boriding treatment at low temperature were carried out with H13 die steel as matrix.The effects of different processes,catalysis of rare earth and low temperature on the structure and properties of the layer were studied.The experimental results are as follows:For the experiments of ordinary boronizing,the optimum formula of boronizing agent is:5%B4C+5%KBF4+5%activated carbon+residual silicon carbide.The thickness of the layer formed by Ni-boronizing is larger than ordinary boronizing.the preferred process of Ni-boronizing was:heating temperature at 980 for 5 h.Compared with ordinary boronizing,the layer of Ni-boronizing also has γ-(Fe,Ni)and(Fe,Ni)2B and(Fe,Ni)B,which gjreatly improves the wear resistance of the material.The hardness of the layer of Ni-boronizing and ordinary boronizing reached a peak at about 25μm from the surface of the sample.The maximum hardness of the layer formed by ordinary boronizing was 1550HV0.1,and the maximum hardness of the layer formed by Ni-boronizing was 1420HV0.1.The hardness of the outer layer of ordinary boronizing was higher than that of Ni-boronizing,and the inner layer was lower than the hardness of the inner layer of Ni-boronizing.The main reason was that the surface of the layer of Ni-boronizing was more loose than ordinary boronizing and there were many defects such as holes.Through the experiments of catalysis of rare earth of H13 steel with different content of CeCl3 is reported,it was found that the thickness of the infiltrated layer is proportional to the content of CeCl3,pack boriding with CeCl3 makes the layer’s structure of H13 steel more compact.When the content of CeC13 is 5%,the density and microhardness of the layer of boronizing are greatly improved,the surface roughness also increased.When the content of CeCl3 is 10%,the surface roughness of the layer of boronizing are greatly improved,but its nicrohardness and density decreased significantly.When the content of CeCl3 in the sample is 0,2.5%,5%and 10%,the friction coefficient reaches the highest value at 440s,610s,850s and 650s.The wear of the samples was sorted from large to small,and the order is:H13 steel sample,ordinary boronizing,2.5%CeC13 assisted boronizing,10%CeC13 assisted boronizing,5%CeC13 assisted boronizing.The wear of the samples ranged from large to small:H13 steel sample,ordinary boronizing,2.5%CeCl3 assisted boronizing,10%CeCl3 assisted boronizing,5%CeC13 assisted boronizing.The friction and wear properties of samples with 5%CeC13 content at high temperature are 1.7 times higher than those of H13 steel matrix.The surface roughness of polished and shot-peened samples was Ra2.06 and Ra1.87 respectively,and the hardness is 18GPa and 23GPa respectively in the low temperature experiments at 580℃.The density of the layer of samples after boronizing and polishing was higher than that of sample after shot peening,the structure of sample’s layer after boronizing and polishing is FeB and Fe2B,and so is the sample after boronizing and spraying.The variation trend of the curves of friction coefficient were similar when these two samples through the boronizing at low temperature after 300℃-700℃.When the experimental temperature was 300℃,the two layers show good friction and wear resistance;when the experimental temperature was 400,500℃ The fluctuation amplitude of the friction curve became larger;When the experimental temperature was 600,700℃,the friction coefficient curve of the two samples had a large difference at the beginning,and the polished sample layer was quickly worn through,losing the protection of the substrate.The coefficient of friction of the shot boring sample first rises,then falls,and finally rises.When the experimental temperature of friction and wear was 300℃,the wear mechanism of the two low temperature samples is mainly fatigue spalling wear and slight oxidative wear;when the temperature was raised to 400℃,the wear mechanism was mainly oxidative wear;near 600℃ wear marks Some flaky wear debris and high temperature fatigue cracks appeared;when the experimental temperature was 700℃,strong oxidative wear appeared in the wear scars,forming a large fatigue peeling pit.