Optimizing Wear Resistance via Brazing Temperature Adaption: Application into CBN/Cu-Sn-Ti Composites
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Due to high hardness, good wear resistance, and excellent thermal stability as well as chemical stability, cubic boron nitride (CBN) is becoming one of most promising materials in grinding alloys possessing high hardness and toughness.[1–5] A variety of technologies have been developed to achieve successful joints between CBN/metal substrates. Among them, direct active brazing has become one of the most widely used and efficient processes.[6–8] Typical examples are Ag-Cu base active fillers.[9] However, Ag-Cu alloys have poor thermal conductivity and oxidation resistance, and their wear resistance and hardness are far from meeting the requirements of modern high-precision machining.[10–12] Cu-Sn eutectic alloys have been demonstrated to be suitable for manufacturing sintered products with a certain porosity and chipping rate.[13,14] The addition of Ti can significantly enhance the bonding between the abrasive and brazing material, thus improving the grinding efficiency.[15,16] Liu et al.[17] evaluated the adhesive strength of the CBN/Cu-Sn-Ti joint interfaces
YONGGANG FAN, JUNXIANG FAN, and CONG WANG are with the School of Metallurgy, Northeastern University, Shenyang 110819, China. Contact e-mail: [email protected] Manuscript submitted June 24, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS B
at different temperatures, and the results suggested that when brazed at 1198 K, the grains were not dislodged from the bond interface. Li et al.[18] showed that adequate bonding strength could be obtained when the brazing temperature was 1213 K. Chen and colleagues,[19] by setting the brazing window spanning 1153 K to 1193 K, unambiguously proved that optimal mechanical properties, including the mean compressive strength and grinding performance, were obtained at 1173 K. However, up to now, a comprehensive investigation on the effects of temperature over the most pertinent properties, such as the porosity, interfacial reaction layer thickness, and, most importantly, abrasive features (weight loss, etc.), of CBN/Cu-Sn-Ti composites is far from complete. Therefore, in the present study, we showcase how a promising cold-pressed CBN/Cu-Sn-Ti composite has been prepared and how the chemical, physical, and mechanical properties vary over a wide range of brazing temperatures from 1173 K to 1273 K, which is of great significance for obtaining high-performance CBN/CuSn-Ti superabrasive products. Table I provides the composition and particle size ranges of the raw materials for brazing. Mixed powder consisting of Cu60Sn40, TiH2 (Beijing Xing Rong Source Technology Co. Ltd., China; purity ‡ 99.99 pct), CBN (Uncoated, Kaifeng Besco Super-hard Abrasive Co. Ltd., China), and a binder (acrylic emulsion) was placed into custom-made molds and pressed by a hydraulic machine (Zhengzhou Research Institute for Abrasives and Grinding Ltd., China; MY-160). After demolding, the specimens (30 mm diameter 9 10 mm height) were placed into the high-temperature vacuum furnace (Shenyang Ke Cheng Vacuum Technology Co. Ltd., China; vacuum level was < 6.0 9 10
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