烧结温度对CBN微晶玻璃结合剂相组成与组织性能的影响

Effect of sintering temperature on phase composition and microstructure and properties of glass-ceramic bond

制备了SiO_2-B_2O_3-Al_2O_3-Li_2O系CBN磨具用微晶玻璃结合剂。采用X衍射分析、热膨胀系数测试、扫描电镜、抗弯强度测试等方法研究了烧结温度对CBN微晶玻璃结合剂相组成、显微形貌和CBN磨具样品力学性能的影响。结果表明:烧结温度高于690℃烧结时,结合剂会析出β-锂霞石(Li_xAl_xSi_(1-x)O_2)相;随烧结温度升高,β-锂霞石晶粒尺寸变大,膨胀系数减小,膨胀系数在740℃达到最小值4.21×10-6K-1;当温度超过740℃时,随温度升高β-锂霞石晶粒变小,含量降低,结合剂膨胀系数增大,烧结温度为840℃时,结合剂变为纯玻璃相。在740℃烧结,结合剂的抗弯强度达到最大值147.8 MPa;在790℃下烧结,CBN砂轮试样的抗弯强度达到最大值64.8 MPa。

A Li2O-Al2O3-SiO2 system glass-ceramic bond used in CBN grinding tools was prepared.The effects of sintering temperatures on phase composition,microstructure of the glass-ceramic bond and mechanical properties of the CBN grinding tools were studied by means of X-ray diffraction analysis,thermal expansion coefficient test,scanning electron microscopy and three-point bending test.The results show that when sintering temperature is over 690 ℃,β-eucryptite（LixAlxSi1-xO2） phase can be precipitated in the bond.As the sintering temperature increasing,the grain size grows and the expansion coefficient of the bond reduces,the expansion coefficient can reach a minimum value of 4.21 × 10^-6K^-1at 740 ℃.When the temperature is over 740 ℃,β-eucryptite crystal begins to dissolve,the expansion coefficient of the bond increases.When the sintering temperature is 840 ℃,the bond is transformed into pure glass phase.When the bond is sintered at 790 ℃,the bending strength of the bond reaches a maximum value of 147.8 MPa.When the CBN grinding wheel is sintered at 790 ℃,the bending strength of the wheel can reach a maximum value of 68.4 MPa.