含氧Zr-B-N纳米复合刀具涂层的结构和性能研究及机理分析

Me-B-N (Me refers transition metals, such as Ti, Cr, Zr, TiAl, CrAl, etc.) nanocomposite tool coatings usually possess low elastic modulus, high toughness and excellent wear resistance due to the existence of soft amorphous BN phase. However, their relatively low high-temperature thermal stability and oxidation resistance limit the further applications on cutters used for high-speed machining. This study takes the Zr-B-N coatings that have better oxidation resistance than other coatings in Me-B-N system as the research object, aims at improving their heat-resisting ability further. By adding an appropriate amount of oxygen into the resulting coatings, the coating oxidation and oxygen diffusion at high temperatures will be suppressed and slowed down by virtue of the solid solution of oxygen atoms or precipitation of ZrO2 phase. The combined techniques of high power impulse magnetron sputtering (HIPIMS) and pulse DC magnetron sputtering are used to produce the Zr-B-O-N nanocomposite coatings with different oxygen contents. Based on the systematic investigation of coating microstructure and various performance (including the room temperature performance and high temperature performance), the influence mechanisms of oxygen addition on the coating microstrusture, mechanical property, tribological behavior, and cutting performance of coated tools will be revealed. Meanwhile, the laws of microstructure evolution of Zr-B-O-N nanocomposite coatings at high temperatures, and the related variations of various performance will also be obtained. The result of this research will further improve the high-speed cutting performance of Zr-B-N series coated tools. It can also be used to guide the design and preparation of the other oxygenous nanocomposite superhard coatings and tool coatings.

Me-B-N（Me包括Ti、Cr、Zr、TiAl、CrAl等）纳米复合刀具涂层因存在软质a-BN相，而具有低弹性模量、高韧性和优异的耐磨性能，但高温热稳定性和抗氧化能力相对较差，严重限制其在高温环境下的使用。本项目以Me-B-N涂层中具有较好抗氧化性能的Zr-B-N涂层为研究对象，拟添加适量氧，通过氧原子的固溶或析出ZrO2相来抑制或减缓高温下涂层氧化和氧元素扩散，提升涂层的耐高温能力。采用高功率脉冲和脉冲直流共溅射技术沉积不同含氧量的Zr-B-O-N涂层，系统研究涂层的组织结构和各项性能（包括室温和高温），揭示氧元素对Zr-B-O-N涂层组织结构、力学性能、摩擦学行为和涂层刀具切削性能的影响规律和机理，获得涂层在高温下的组织结构演变规律、及与此相关的各种性能变化规律。本项研究成果将进一步提升Zr-B-N涂层刀具的高速切削性能，同时也可指导其他含氧纳米复合超硬涂层和刀具涂层的设计与制备。

Me-B-N（Me 指Ti、Cr、Zr、TiAl、CrAl 等）系列纳米复合涂层具有较高的韧性和耐磨性能，有望用于切削刀具表面，但在高温热稳定性和抗氧化性能方面略显不足，由于涂层中的BN相在300℃以上开始氧化，生成可挥发的BOx，严重限制其在高速切削、干切削等高温环境下的使用。为解决这一问题，本项目以具有高硬度和高熔点的ZrB2涂层和高韧性的Zr-B-N 纳米复合涂层为研究对象，通过添加适量氧元素来改善其耐热能力。实验采用了高功率脉冲磁控溅射和脉冲直流磁控溅射复合镀膜技术，制备了一系列不同氮、氧含量的Zr-B-O-N纳米复合涂层，对涂层沉积工艺、成分和组织结构、硬度和结合强度等力学性能、摩擦学行为、涂层热处理后结构和性能的变化、以及涂层刀具的切削性能都进行了系统研究。结果表明，少量的氧元素添加到涂层内，氧原子以固溶的形式存在于ZrN/ZrB2晶格中，随着涂层内氧含量的增加，逐渐沉淀析出具有良好耐热性能的ZrO2相，它在高温下能够阻止外界氧向涂层内扩散，同时也减缓了涂层内氧元素的扩散，从而增强涂层的抗氧化能力和热稳定性。另外，涂层内ZrO2相也起到了一定的减摩作用，涂层在接触摩擦过程中也生成了少量的硼酸盐，同样具有很好的润滑作用，又进一步提升了涂层的耐磨性能。对淬硬钢的切削试验表明，Zr-B-N涂层刀具在切削过程中产生了明显的高温氧化现象，前刀面上形成了积屑瘤，而Zr-B-O-N涂层刀具在完成切削后前、后刀面仍然保持平整光滑，表现出较高的抗高温氧化性能，这是由于涂层中添加氧元素后进一步细化了涂层组织，生成了具有一定减摩作用的连续致密抗氧化膜，能阻止高温下氧元素向涂层内扩散，故提高了刀具的切削性能和使用寿命。本项目研究获得了一种可切削淬硬钢的Zr-B-O-N纳米复合刀具涂层的制备工艺，揭示了氧元素对 Zr-B-O-N 涂层组织结构、力学性能、摩擦学行为和涂层刀具切削性能的影响规律和机理，获得了涂层在高温下的组织结构演变规律、及与此相关的各种性能变化规律，对其他含氧纳米复合涂层的研发具有一定的指导意义。