难熔金属注射成形的研究

Study on Injection Forming of Refractory Metal Powder

采用金属粉末注射成形技术成功制得了形状复杂的纯钨和纯钼零件。粉末注射成形工艺为:粉末装载量为52%,注射温度为165℃,注射压力为65 MPa,溶剂脱脂+热脱脂两步脱脂法,经2300℃氢气气氛烧结,钨烧结样品的密度可达18.26 g.cm-3,相对密度为94.61%;经1900℃氢气气氛烧结,钼烧结样品的密度为9.7 g.cm-3,相对密度达95.09%,制品尺寸精度控制在±0.3%以内。同时,通过实验对比研究了掺加少量的稀土氧化物(La2O3,Y2O3)对注射成形钨和钼制品性能的影响。实验结果表明:稀土元素氧化物的添加,提高了注射成形钨和钼制品烧结后的密度,明显细化了烧结后样品的晶粒,稀土氧化物作为第二相粒子弥散分布于晶界处,提高了注射成形钨和钼制品的强度。

Adopting the technology of metal powder injection forming complex shape parts of pure tungsten and molybdenum were produced successfully. The technical parameters of the injection forming were that the loading is 52% in volume ratio, injection temperature 165 ℃, injection pressure 65 MPa and debinding used solvent plus thermal debinding method. After sintering at 2300 ℃ in hydrogen atmosphere, the density of pure tungsten parts could reach 18.36 g·cm^-3, and its relative density was 95.12%. After sintering at 1900 ℃ in hydrogen atmosphere, the density of pure molybdenum parts could reach 9.70 g·cm^-3, and the its relative density was 95.09%. The size precision of these parts was controlled in ± 0.3%. By experiments the influences of adding a small amount of rare earth oxides, such as La2O3 and Y2O3 on the properties of the tungsten and molybdenum products were also studied. The results indicated that： addition of the rare earth oxides improved densities of pure tungsten and pure molybdenum products after sintering, and refined the grain size of the products obviously. The rare earth oxide as a second phase in the matrix distributed at grain boundary, which prevent dislocations from moring and grains from growing when sintered at high temperatures. So that the strength and the ductility of the products were also increased.