Preparation Technology And Mechanical Properties Of High Chromium Alloy Matrix Composites Reinforced By Zirconium Corundum Particles

A new zirconium corundum particle reinforced high chromium alloy composite has been prepared successfully by vacuum pressureless sintering with fused zirconium corundum particles and high chromium alloy powders as raw materials.The effect of processing technology on the microstructure mechanical properties was investigated by using optical microscope,scanning electron microscope（SEM）equipped with energy dispersive spectrometer（EDS）,X-ray diffraction（XRD）and differential thermal analysis（DTA）.The conclusions are drawn as follows:After sintered at 1200 ?C for 30 min,the microstructure of the high chromium alloy without addition of zirconium corundum particles consists of pearlite,martensite and granular Fe_1.1Cr_0.9B_0.9（M₂B）phase.The sintered high chromium alloy was heat-treated at 1050 ?C for 2h followed by furnace cooling and air cooling,respectively.Under the condition of furnace cooling,the pearlite is still exist,while in the air-cooling condition,the pearlite disappears completely and microstructure is consisted of martensite and Fe_1.1Cr_0.9B_0.9 particles.The high chromium alloy has the highest hardness and bending strength after heat treated at 1050℃ for 2h followed by air cooling.With the increasing of sintering temperature between 1160¹220℃ and the same holding time（30min）,the bending strength of zirconium corundum particle reinforced high chromium alloy composite increases first,and then decreases.After sintered at 1200℃,the composite has a dense microstructure with the granular M₂B precipitates in it,and has a maximum bending strength.When the sintering temperature is below 1180?C,there are many holes in the composite.When the sintering temperature is 1220℃,the bone-like precipitates appear in the microstructure,which causes the bending strength of composite decrease.There exists interface reaction layer between zirconium corundum particle and high chromium alloy matrix.During sintered at 1200℃,the thickness of the reaction layer increases with the extension of holding time.The bending strength of the composite increases first and then decreases with holding time,and gets the maximum at holding time of 30 min.Based on the analysis of the interface reaction layer,it is indicated that the following reactions may occur during sintering of zirconium corundum and high chromium alloy :ZrO₂ + [Si]_Fe + [B]_Fe → Zr（O,Si,B）₂+ SiO₂When the mass fraction of the zirconium corundum particles is the same,the bending strength of the composite increases with the increase in particle size between 50 2000 μm,While the particle size is the same,the bending strength of the composite decreases with increasing the mass fraction of the zirconium corundum particles.The variation of the mechanical properties of the composite is related to the interfial bonding strength between zirconium corundum particles and high chromium alloy matrix.