84 / 2021-06-30 16:06:40

Plasma diagnosis revealing the nitrogen deficiency in Cr-N coatings deposited by reactive HiPIMS

high power impulse magnetron sputtering, reactive sputtering, reactive mode, chromium nitride coating, plasma diagnostics

Cr-based nitride coating has excellent mechanical properties and corrosion resistance, which has a promising application prospect in seawater environments that require wear resistance and corrosion resistance. The component and microstructure of nitride coatings prepared by reactive magnetron sputter method are mainly determined by the reactive gas flow rate. Normally, reactive sputter can be divided into three different modes, namely, the metallic mode, transition mode, and compound mode. As a kind of short pulse and low duty cycle discharge, high power impulse magnetron sputtering (HiPIMS) has the characteristic of high ionization, which makes it possible to prepare dense coatings without large particle defects at low temperature. However, the hysteresis effect of reactive HiPIMS is still unclear, and the temporal and spatial evolution characteristics of plasma still need to be studied. In this work, Cr-N coatings were prepared by reactive HiPIMS under different sputter modes (nitrogen flow rate range: 0~90 sccm). The composition and microstructure of Cr-N coatings were characterized. The variation of plasma parameters was also investigated. We found that the hysteresis behavior of reactive HiPIMS for Cr-N coatings was not obvious. From metallic mode to compound mode, the peak electron density decreased from 5.1×10¹⁷ /m³ to 2.2×10¹⁷ /m³, especially the density of hot electrons was improved with the increase of nitrogen flow rate. Coatings deposited in transition zone demonstrated similar component and structure. Due to the insufficient decomposition and ionization of N₂ molecules in the low-density discharge mode of HiPIMS, serious lack of N was suffered in the Cr-N coatings.