预扩散处理对原位生成TiC_p/Fe基粉末冶金复合材料组织与性能的影响

将水雾化Fe粉与Ni粉、Mo粉、Ti粉混合均匀,然后在800℃、50%H2+50%Ar(体积分数)气氛保护下进行预扩散处理,将预扩散粉与电解Cu粉和石墨粉混合,通过压制与烧结,制备Ti C颗粒增强Fe基复合材料。通过X射线衍射分析、扫描电镜及能谱分析和力学性能测试等手段,研究预扩散处理对原位生成Ti Cp/Fe基粉末冶金材料组织与性能的影响。结果表明:Fe-Ni-Mo-Ti混合粉在800℃下预扩散处理后形成表面粗糙的团球状预扩散粉末颗粒,但合金元素在Fe粉颗粒内分布不均匀。与用混合粉制成的Ti Cp/Fe基复合材料相比,用预扩散粉制备的材料孔隙率略有增加。随预扩散时间延长,材料中富Ti区的尺寸减小,组织明显细化,珠光体分布更均匀,同时形成大量弥散分布的粒径在0.1~0.5μm的Ti C颗粒。材料的硬度和抗弯强度都随原料粉预扩散时间延长而提高,用60 min预扩散粉制成的Ti Cp/Fe基复合材料的硬度HRB和抗弯强度分别达到63.6和613.7 MPa,比用混合粉制成的Ti Cp/Fe基复合材料分别提高11.8%和38.3%。用预扩散粉末制备的Fe基复合材料的断裂形式为具有一定韧性断裂特征的脆性断裂。

Effects of diffusion alloying treatment on microstructure and properties of in-situ synthesized TiCp/Fe-based PM materials

Water atomized Fe powders were well-mixed with Ni, Mo and Ti powders and then diffusion alloyed at 800℃ in 50% H2 +50% Ar atmosphere. Cu and graphite powders were ball-milled with the diffusion alloyed powders to compact the green samples, then sintered at 1 160℃ in 50% H2+50% Ar atmosphere to prepare the TiC particles reinforced Fe-based PM materials. The effects of diffusion alloying treatment on microstructure and properties of TiCp/Fe-based PM materials were investigated by XRD, SEM, EDS and mechanical property tests. The results show that spherical diffusion alloyed particles with rough surface are formed on the Fe-Ni-Mo-Ti mixed powder after diffusion alloyed at 800℃, but the distribution of alloying elements is unevenly in the particles. The porosity of the TiCp/Fe-based PM materials prepared by diffusion alloyed powders increases a little compared with that of the PM materials prepared by mixed powders. With increasing the diffusion time, the size of Ti-riched zone of the TiCp/Fe-based PM materials decreases, the microstructure is obviously refined, and the distribution of pearlite is more uniform. Meanwhile, a largenumber of TiC particles with size of 0.1?0.5μm are in-situ synthesized homogeneously. Both the hardness and the bending strength increase with increasing diffusion time, and the hardness and the bending strength of the Fe based composites prepared by 60min diffusion alloyed powders reach to 63.6 HRB and 613.7 MPa, respectively, which are 11.8%, 38.3% higher than that of the composites prepared by mixed powders. The fracture mode of samples prepared by diffusion alloyed powders is brittle fracture with some ductile fracture characteristics.