纳米CrNx涂层相组成、结构及力学性能研究

Phase Composition of Nano-CrNx Coating and Its Effect on Mechanical Properties

摘要:

采用高功率调制脉冲磁控溅射（Modulated Pulsed Power magnetron sputtering, MPPMS）和脉冲直流磁控溅射（Pulsed Direct Current magnetron sputtering, PDCMS）复合沉积CrNx涂层，通过调节氮气流量比及溅射功率，研究了氮气/氩气流量比、PDCMS溅射功率及MPPMS溅射功率等工艺参数对CrNx涂层成分、相组成、微结构和力学性能的影响。通过电子探针（EPMA）、X射线衍射仪（XRD）、扫描电子显微镜（SEM）、纳米压痕仪及维氏硬度计等，分别对CrNx涂层的成分、相组成、微结构、形貌、硬度及断裂韧性等进行了表征。当PDCMS溅射功率从700 W增加到1000 W，MPPMS峰值功率增加43.5%，涂层中Cr含量由61.0 at.%增加到65.4 at.%，N含量由39.0 at.%减少到34.6 at.%，而CrNx涂层主要由Cr2N相组成。随着溅射功率的增加，CrNx涂层硬度变化不大，均在20 GPa左右，而涂层的致密性和断裂韧性均得到明显提升。流量比由15%增加至50%，MPPMS的峰值电流和峰值功率先减小后增加，涂层的物相逐渐由Cr2N向CrN转变。当氮气流量比为35%时，CrNx涂层由Cr2N和CrN两相组成，受两相结构的影响，CrNx涂层的硬度值、残余压应力值和断裂韧性值均达到最大值，分别为20.5 GPa、-901.8 MPa和6.5 MPa·m1/2。电子温度应为CrNx涂层相结构变化的主要驱动力，致密性和两相结构是影响CrNx涂层断裂韧性的主因。

Abstract:

Modulated pulsed power magnetron sputtering (MPPMS) and pulse direct current magnetron sputtering (PDCMS) were employed to deposit CrNx coatings by controlling the nitrogen/argon flow ratio and sputtering power, respectively. The influence of nitrogen flow ratio as well as sputtering power of MPPMS and PDCMS were systematically studied to learn the roles of process parameters on CrNx coatings composition, phase, microstructure and mechanical properties. The composition, phase, microstructure, morphology, hardness as well as fracture toughness of coatings were characterized through electron probe micro analysis (EPMA), X-ray diffractometer (XRD), scanning electron microscope (SEM), nanoindentation device. As the PDCMS sputtering power increased from 700 W to 1000 W, the peak power of MPPMS showed an increase of 43.5%. The Cr elements in the coatings were ranging from 61.0 at.% to 65.4 at.%, while N contents decreased from 39.0 at.% to 34.6 at.%. The CrNx coatings were mainly composed of Cr2N phase without obvious changes. With the increase of the sputtering power, the hardness of the CrNx coatings was about 20 GPa, while the fracture toughness of the coatings was improved significantly. Changing the flow ratio from 15% to 50%, the peak current of MPPMS first decreased followed by an increase, the phase structure of the coatings gradually varied from Cr2N to CrN. When the nitrogen flow ratio was about 35%, the CrNx coatings were mainly composed of Cr2N and CrN. And the hardness, residual compressive stress and fracture toughness of the CrNx coating all attained their maximum values of 20.5 GPa, -901.8 MPa and 6.5 MPa·m1/2, respectively. The electron temperature should be the driving force for phase structure variation for CrNx coatings, and the dense and two-phase microstructure controlled the toughness of CrNx coatings.