Micro-fracture mechanism of polycrystalline CBN grain during single grain scratching tests based on fractal dimension analysis

• Published in: Precision engineering Vol. 59; pp. 26 - 36
• Main Authors: Zhu, Yejun, Ding, Wenfeng, Rao, Zhiwen, Yang, Changyong
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.09.2019
• Subjects: Fractal dimension; Grinding wheel speed; Micro-fracture; PCBN grain; Undeformed chip thickness; Micro-fracture; PCBN grain; Undeformed chip thickness; Fractal dimension; Grinding wheel speed
• ISSN: 0141-6359; 1873-2372
• DOI: 10.1016/j.precisioneng.2019.05.010

The wear phenomenon is an important issue that affects the grinding performance of polycrystalline cubic boron nitride (PCBN) grinding wheel. To explore the wear mechanism, single grain scratching tests were conducted on the nickel-based superalloy Inconel 718. Fractal theory was applied to evaluate the grain wear process, and the influences of undeformed chip thickness agmax and grinding wheel speed vs on grain wear were analysed. The variation in fractal dimension, grinding force and grinding force ratio were discussed. Results show that the micro-fracture is caused by the crack, and the adhered grinding chip leads to the attrition wear of PCBN grain. The average specific material removal volume of monocrystalline CBN grain is approximately 10.7% that of PCBN grain when macro-fracture occurs. The effect of agmax on grain macro-fracture is stronger than that of vs. Furthermore, the grinding parameters should be set as follows: vs of 80 m/s and agmax in the range of 0.1–0.67 μm. These settings help improve the grain micro-fracture phenomenon in high-speed grinding. •Single grain scratching tests were conducted to study PCBN grain wear.•Micro-fracture is caused by crack and attrition wear is caused by grinding chip.•Material removal volume of MCBN is about 10.7% of PCBN grain when macro-fracture occurs.•The optimal grinding wheel speed is set as 80 m/s.•The optimal undeformed chip thickness is in the range of 0.1–0.67 μm.