超高速单层钎焊多晶CBN超硬砂轮自锐问题研究

Ultrahigh speed grinding technology has unique advantage and broad prospect in high efficiency machining difficult-to-cut materials with high strength and high toughness, for example, nickel superalloy. However, the ultrahigh speed abrasive wheels with traditional monocrystalline CBN grains could not enjoy long-term durability of high edge sharpness. The reason is that it is very difficult to micro-fracture for the monocrystalline CBN grains. The problem mentioned above has hindered the increase of the machining efficiency during ultrahigh speed grinding.In this project, it is put forward to develop ultrahigh speed abrasive wheels with multicrystalline CBN grains. By solving the internal cause and the external one of the micro-fracture behavior of the multicrystalline CBN grains based on the coordination control of the brazing stress and the grinding force, the self-sharpening behavior of the abrasive wheels is controlled. The problem, that the long-term durability of high edge sharpness of the abrasive wheels could not be ensured, is therefore overcome. The main contents are as follows: controlling method and mechanism of the brazing stress of the multicrystalline CBN grains, distribution model of the grains on the ultrahigh speed abrasive wheel constrained by the grinding force, coordination control of the brazing stress and the grinding force based on the grains micro-fracture, self-sharpening behavior evaluation of the single-layer brazed multicrystalline CBN abrasive wheels for ultrahigh speed grinding. Based on this research project, the scientific basis could be established for the development of the single-layer brazed multicrystalline CBN abrasive wheels with good wheel safety, high edge sharpness, strong grain bonding for ultrahigh speed grinding.It is of theoretical and practical significance to realize high efficiency grinding of difficult-to-cut materials with high strength and high toughness for long-term durability.

超高速磨削技术在以镍基合金为代表的强韧性难加工材料高效加工领域具有独特优势和广阔前景，但传统单晶CBN磨粒制作的超高速砂轮难以通过磨粒微破碎自锐而实现砂轮高锋利度的长时稳定保持，这已成为制约超高速磨削效率提高的关键问题。本项目提出研制超高速单层钎焊多晶CBN超硬砂轮，通过钎焊残余应力与磨削力的协同约束解决影响多晶CBN磨粒微破碎的内因与外因问题，实现砂轮自锐行为的主动控制，攻克如何长时稳定保持砂轮高锋利度的难题。研究内容包括：多晶CBN磨粒钎焊残余应力控制方法与机理、磨削力约束的超高速砂轮磨粒分布阵列设计模型、基于磨粒微破碎控制的残余应力与磨削力协同约束、单层钎焊多晶CBN砂轮超高速磨削自锐性能评价。项目的完成可为研制满足砂轮安全性、磨粒把持力、砂轮锋利度综合要求的超高速单层钎焊多晶CBN超硬砂轮奠定科学基础，对于实现强韧性难加工材料长时稳定的高效率磨削具有重要理论和实际意义。

超高速磨削是难加工材料高效精密加工的重要方法，也是现阶段先进制造技术领域的研究热点。但是，普通树脂、陶瓷、金属结合剂砂轮无法满足超高速磨削工艺对砂轮安全性、磨粒把持力与砂轮锋利度的要求，而钎焊单晶立方氮化硼（CBN）超硬磨料砂轮由于单晶磨粒在力学性能方面各向异性的特点，易发生解理破碎，从而降低了砂轮的耐用度，仍然无法满足超高速磨削对CBN砂轮锋利度及其保持能力的高要求，导致落后的工具与配套工艺技术成为制约难加工材料超高速磨削技术发展的瓶颈。有鉴于此，本项目提出研制超高速单层钎焊多晶CBN超硬砂轮的构想。通过协同约束钎焊残余应力与磨削力以控制多晶CBN磨粒的微破碎行为，解决砂轮自锐难题，为实现超高速磨削过程中砂轮高锋利度的长时稳定保持提供理论与技术支持。.主要工作包括： .（1）采用复合钎料实现了多晶CBN磨粒的高质量钎焊连接，结合实验与仿真阐明了多晶CBN磨粒内部钎焊残余应力的分布规律与形成机制，提出了钎焊残余应力的控制策略；.（2）通过单颗磨粒磨削实验与钎焊砂轮磨削实验，揭示了砂轮承受的总磨削力与单颗磨粒承受的磨削力之间的联系，阐明了磨削工艺条件对磨削负荷的影响规律； .（3）提出并实现了采用分形维数对磨粒的微破碎程度进行定量表征，建立了多晶CBN磨粒微破碎特性、钎焊残余应力和磨削力负荷三者之间的关系模型。在此基础上，实现了基于磨粒微破碎控制的残余应力与磨削力范围协同确定。.（4）综合评价了单层钎焊多晶CBN砂轮超高速磨削的自锐性能，从磨削力、磨削比能、磨削温度角度阐明了超高速磨削工艺对单层钎焊多晶CBN砂轮磨损行为的影响规律。揭示了单层钎焊多晶CBN砂轮的磨损机理，提出了磨损抑制策略，最后完成了典型强韧性难加工材料超高速高效磨削验证。