Influence of rare earth nanoparticles and inoculants on performance and microstructure of high chromium cast iron

The high chromium cast irons (HCCIs) with rare earth (RE) nanoparticles or inoculants were fabricated in the casting process. The phase compositions and microstructure were analyzed by X-ray diffraction (XRD) and optical microscopy (OM), respectively. The hardness and impact toughness were tested by Rockwel-hardmeter and impacting test enginery. And then, the morphology of fracture was researched by scanning electron microscopy (SEM). The results demonstrated that the phase compositions of HCCIs with addition of RE nanoparticles or inoculants which were M7C3 carbides + α-Fe did not change obviously. However, the prime M7C3 carbides morphology had great changes with the increase of RE nanoparticles, which changed from long lath to granular or island shape. When the content of RE nanoparticles was 0.4 wt.%, the microstructure of high chromium cast iron was refined greatly. The microstructure of carbides was coarser when the addition of RE nanoparticles was higher than 0.4 wt.%. The hardness and impact toughness of HCCIs were improved by addition of RE nanoparticles or inoculants. The impact toughness of HCCIs was increased 36.4% with RE nanoparticles of 0.4 wt.%, but the hardness changed slightly. In addition, the adding of RE nanoparticles or inoculants could reduce the degree of the brittle fracture. Fracture never seemed regular, instead, containing lots of laminates and dimples with the increase of the RE nanoparticles. The results also indicated that the optimal addition amount of the RE nanoparticles was 0.4%, under this composition, the microstructure and mechanical property achieved the best cooperation. In addition, through the study of erosion wear rate, when adding 0.4% RE nanoparticles into the HCCIs, the erosion wear rate got the minimum 0.32×10-3 g/mm2, which could increase 51.5% compared with that without any RE nanoparticles.     

WC-Co硬质合金材料的纳米稀土改性

本文简要综述了哈尔滨工业大学纳米表面工程课题组最近十年来在硬质合金材料纳米改性方面的一些研究成果。稀土对硬质合金性能有明显的改善作用,但大多数研究都是在硬质合金中加入微米级的稀土。纳米表面工程课题组利用纳米材料的小尺寸效应、表面和界面效应等特征,通过向传统的WC硬质合金粉末料中(其中Co的质量分数为8%和11%)加入微量纳米级(50 nm)稀土改性剂进行强韧化改性,分别利用真空烧结和放电等离子烧结得到硬质合金块体。与现有的其它同成分硬质合金对比分析,纳米稀土改性后硬质合金的性能得到显著地提高,达到了既不提高很大成本又能提高使用性能的目的。     

纳米改性Cr-Mo-Cu合金铸铁的石墨形态及其性能

采用X射线衍射仪、扫描电子显微镜及硬度计对纳米改性前后的Cr-Mo-Cu合金铸铁进行了显微组织观察、XRD物相分析和硬度测定,并在生产中考查了由Cr-Mo-Cu合金铸铁制成的光球磨板的磨削加工效率及使用寿命.结果表明,纳米改性后Cr-Mo-Cu合金铸铁中的石墨由形态粗长、数量较少的片状变成了形态细短、数量较多且分散的蠕虫状,晶粒明显细化;XRD衍射峰发生宽化和偏移;洛氏硬度显著提高;制成的Cr-Mo-Cu合金铸铁光球磨板磨削效率和使用寿命均有十分显著的增加.     

一种新型高性能复相陶瓷材料的应用前景

传统Al2O3/TiO2复相陶瓷韧性低,可靠性难以保证.将纳米技术引入到该领域,通过把纳米尺度的氧化铝和氧化钛粉末再造粒成为纳米结构的氧化铝/氧化钛(Al2O3/TiO2)复合氧化物粉末并采用新型工艺路线制备的精细结构Al2O3/TiO2复相陶瓷,与传统微米级晶粒尺度的Al2O3/TiO2复相陶瓷相比,其强度、韧性和耐...