基于TiC_(0.5)N_(0.5)/Si_3N_4复相陶瓷基体的PVD及CVD涂层刀具性能

首先,以15vol%或25vol%的TiC0.5N0.5粉体为导电第二相,利用热压烧结法制备了TiC0.5N0.5/Si3N4复相陶瓷;然后,分别通过物理气相沉积(PVD)和化学气相沉积(CVD)技术在TiC0.5N0.5/Si3N4陶瓷刀具表面沉积了CrAlN和TiN/Al2O3/TiN涂层;最后,通过对TiC0.5N0.5/Si3N4刀具进行连续切削灰铸铁实验,研究了TiC0.5N0.5含量和涂层类型对刀具磨损特征的影响,并探讨了刀具的磨损机制。结果表明:TiC0.5N0.5含量的增加有利于提高TiC0.5N0.5/Si3N4复相陶瓷刀具基体的硬度和电导率,但对耐磨性和切削寿命的影响较小;采用PVD技术沉积CrAlN涂层时,随着TiC0.5N0.5含量的增加,涂层的厚度、结合强度和硬度都得到提高,涂层刀具的磨损性能显著提高,切削寿命也明显延长;而采用CVD技术沉积TiN/Al2O3/TiN涂层时,TiC0.5N0.5含量的变化对涂层的厚度、结合强度和硬度基本没有影响,TiN/Al2O3/TiN涂层刀具整体切削性能变化不大。CrAlN涂层和TiN/Al2O3/TiN涂层都可明显改善TiC0.5N0.5/Si3N4复相陶瓷刀具的耐磨性和切削寿命;相对于TiN/Al2O3/TiN涂层,CrAlN涂层具有更高的涂层硬度和粘着强度,但TiN/Al2O3/TiN涂层具有较大的涂层厚度,TiN/Al2O3/TiN涂层刀具表现出更加优异的耐磨性和切削寿命。TiC0.5N0.5/Si3N4复相陶瓷刀具的磨损机制以机械摩擦导致的磨粒磨损为主,伴随有少量的粘结磨损。

Performances of PVD and CVD coated tools based on TiC0.5N0.5/Si3N4 composite ceramic matrix

Firstly, TiC_0.5N_0.5/Si₃N₄ composite ceramics were prepared by hot-pressing method using 15vol% or 25vol% TiC_0.5N_0.5 powders as conducting second phase. Then, CrAlN and TiN/Al₂O₃/TiN coatings were deposited on the surfaces of TiC_0.5N_0.5/Si₃N₄ ceramic tools by physical vapor deposition (PVD) and chemical vapor deposition (CVD) technologies, respectively. Finally, the effects of TiC_0.5N_0.5 content and coating type on tool wear characteristics were investigated by conducting continuous cutting experiments for gray cast iron on TiC_0.5N_0.5/Si₃N₄ tools, and the wear mechanisms of tools were also discussed. The results show that the increasing of TiC_0.5N_0.5 content is beneficial to enhance the matrix hardness and conductivity of TiC_0.5N_0.5/Si₃N₄ composite ceramic tools, but has little effect on wear resistance and cutting length. When depositing CrAlN coating by PVD technology, with TiC_0.5N_0.5 content increasing, the thickness, adhesion strength and hardness of coating increase, the wear performances of coated tools enhance significantly, and cutting length extends obviously. However, when depositing TiN/Al₂O₃/TiN coating by CVD technology, the variation of TiC_0.5N_0.5 content almost has no effects on coating thickness, adhesion strength and hardness, as well as the comprehensive cutting performances of TiN/Al₂O₃/TiN coated tools change little. Both of CrAlN coating and TiN/Al₂O₃/TiN coating can improve the wear resistance and cutting length of TiC_0.5N_0.5/Si₃N₄ composite ceramic tools significantly. Compared with TiN/Al₂O₃/TiN coating, CrAlN coating has higher coating hardness and adhesion strength; while TiN/Al₂O₃/TiN coated tool shows more excellent wear resistance and cutting length for TiN/Al₂O₃/TiN coating has larger coating thickness. The main wear mechanism of TiC_0.5N_0.5/Si₃N₄ composite ceramic tools is abrasive wear caused by mechanical friction, and associated with a small amount of adhesive wear.