Improving strength and toughness of vitrified bond by adding nano-rare earth oxides
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摘要: 为提高CBN砂轮用陶瓷结合剂的强度与韧性,以不同体积分数的纳米CeO2、Sm2O3、Y2O3、La2O3、Er2O3与基础结合剂形成复合结合剂,并通过X射线衍射仪和扫描电子显微镜表征其物相和显微结构,通过三点弯曲、单边切口梁等测试方法测试其机械性能。实验结果表明:添加体积分数2%的纳米CeO2或纳米Er2O3后,试样的抗折强度分别为187 MPa和194 MPa,比基础结合剂的165 MPa分别提高了13.3%和17.6%,而其他3种纳米稀土氧化物没有表现出增强作用。5种纳米稀土氧化物均可增加基础结合剂的韧性,但Er2O3的效果最明显,在体积分数为2.5%时,试样的断裂韧性为2.7 MPa·m1/2,比基础结合剂的1.3 MPa·m1/2提高了108.2%。以含纳米Er2O3体积分数2%的复合结合剂与CBN磨料(浓度200%)混合制备试样,发现该复合结合剂对CBN颗粒的润湿良好,试样的抗折强度为102 MPa。Abstract: To improve the strength and toughness of vitrified bond in CBN grinding wheel, composite bonds are prepared by adding different fractions of nano-sized CeO2, Sm2O3, Y2O3, La2O3 or Er2O3 as additives. X-ray diffractor (XRD) and scanning electron microscope (SEM) are used to analyze their phases and micro structures, and three-point bending test and single-edge notched beam test to indicate their mechanical properties. Results show that the flexural strengths of samples with 2vol% Ce2O or Er2O3 are 187 MPa and 194 MPa, respectively, which are 13.3% and 17.6% higher than 165 MPa of basic bond, while the other oxides could not improve the strength. On the other hand, all the five oxides could improve the fracture toughness and Er2O3 does the best by 2.7 MPa·m1/2 at 2.5vol%, i.e. 108.2% higher than 1.3 MPa·m1/2 of the basic bond. The composite bond with 2vol% nano-Er2O3 and CBN grains (concentration 200%) are used to prepare test samples, which possess good bonding between bond and grain and flexural strength of 102 MPa.
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Key words:
- vitrified bond /
- nano rare earth oxides /
- flexural strength /
- fracture toughness
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