Squeeze Casting Infiltration Fabrication And Properties Research Of 5CrMnMo-3YSZ Composite Die Materials

In this paper,aiming to resolve the bottlenecks about low service life and poor service performance of the dies in squeeze casting process for high melting point alloy,the technical route for the fabrication of 5Cr Mn Mo-3YSZ composite die materials was sought,starting from connection process exploration between metal and ceramics.The preparation processes of 3YSZ（3 mol.%Y₂O₃ stabilized Zr O₂）porous ceramic preform was optimized,and 5Cr Mn Mo-Ni Cr Co Al Y/3YSZ composite die materials with excellent high temperature performance and good thermal shock resistance were prepared,so as to improve the service life of squeeze casting die for high melting point alloy and reduce the production cost of high melting point alloy squeeze casts.Firstly,the exploratory preparation tests of 5Cr Mn Mo-3YSZ multi-layer die materials were carried out by plasma spraying,hot pressing sintering and ceramic injection molding process,respectively.It was found that the thickness of 3YSZ ceramic layer in 5Cr Mn Mo-3YSZ multi-layer material samples prepared by plasma spraying process was limited,and that the remelt and plastic deformation of die steel matrix both occurred in 5Cr Mn Mo-3YSZ multi-layer material samples prepared by hot pressing sintering process or ceramic injection molding process.The die performance and connection strength of 5Cr Mn Mo-3YSZ multi-layer material prepared by the above three processes were not ideal.On this basis,a new technical route to fabricate 5Cr Mn Mo-3YSZ composite die material by combining porous ceramic prefabrication and infiltration bonding process was proposed.In this paper,the improved Monte Carlo model was adopted to simulate and analyze the influence of sintering temperature,sintering time,solid phase diffusion rate,vacancy shrinkage rate and other factors on microstructure change rules of 3YSZ porous ceramics during sintering.Particle accumulation method was used to verify the simulation system,indicating that the system in this paper could simulate the sintering behavior of 3YSZ porous ceramics quickly and efficiently.3YSZ porous ceramic was optimized by adding pore-forming agent and particle stacking method.The effects of different pore-forming agents,pore-forming agent content,sintering temperature,sintering time and second phases on microstructures and properties of3YSZ porous ceramics were studied,especially the influence on the fracture toughness and infiltration properties.Ni Cr Co Al Y/3YSZ multiphase porous ceramics with high fracture toughness were prepared by sintering at 1500°C for 2h with 15wt.%25μm PMMA and 10wt.%Ni Cr Co Al Y.The porosity,compressive strength,flexural strength and fracture toughness of porous ceramics were 43.83%,257.55 MPa,79.96MPa and 4.75 MPa?m^1/2,respectively.The infiltration performance test showed that the infiltration ability of 3YSZ porous ceramics changed slightly with the increase of pore-forming agent content,sintering temperature and sintering time.3YSZ porous ceramics prepared in this paper showed ideal infiltration properties,which could meet the experimental requirements of subsequent infiltration connection between5Cr Mn Mo metal and 3YSZ porous ceramics.The calculation formulas of critical infiltration pressure and infiltration depth were calculated and deduced by theoretical analysis of squeeze casting infiltration process.When the ceramic particle size was larger and the porosity was higher,the critical infiltration pressure was smaller.The higher the infiltration temperature and the longer the holding time was,the deeper the infiltration depth was.In infiltration connection process,pore shape of porous ceramics affected the transmission of stress and heat,and further changed the distribution of stress and temperature field.The porous ceramics with spherical pores were most conducive to infiltration connection.Considering theoretical calculation and simulation analysis results,the optimum technical scheme of infiltration connection was determined:mold preheating temperature,preheating temperature of porous ceramic preform,infiltration temperature,speed of equipment,infiltration pressure,and holding time was 330-370°C,800-850°C,1550±20°C,5mm/s,45MPa,and 45s,respectively.The microstructures and properties of 5Cr Mn Mo-3YSZ and 5Cr Mn Mo-Ni Cr Co Al Y/3YSZ composites were analyzed.Simple 5Cr Mn Mo-Ni Cr Co Al Y/3YSZ composite mould was fabricated.The Ni Cr Co Al Y phase improved the infiltration behavior of 5Cr Mn Mo in 3YSZ,resulting in that the shear strength of 5Cr Mn Mo-Ni Cr Co Al Y/3YSZ composite was strengthened and reached 189.63 MPa and the thermal vibration cycle number reached 136 times.The simple mould showed ideal microstructures and good performance:the shear strength was 169.19 MPa,the thermal vibration cycle number was 115,the wear rate was 3.784 mg/（km?N）,and the thermal conductivity at 800°C was 5.47 W/（m·°C）.The 5Cr Mn Mo-Ni Cr Co Al Y/3YSZ composite in this paper could be used to fabricate the forming dies for squeeze casting of high melting point alloy.In terms of the application in this paper,3YSZ porous ceramic preform and Al₂O₃ porous ceramic wear-resistant ring were prepared by foam method.The continuous 3YSZ ceramic reinforced 5Cr Mn Mo composite and continuous Al₂O₃ ceramic reinforced aluminum alloy parts fabricated by squeeze casting infiltration process showed excellent wear resistance and bonding properties,which had practical application value for the preparation of composite materials and the industrial production of products.