Abstract
In this study, AlCrN coatings were deposited using modulated pulsed power magnetron sputtering (MPPMS) with different power pulse parameters by varying modulated pulsed power (MPP) charge voltages (350 to 550 V). The influence of power pulse parameters on the microstructure, mechanical properties and thermal stability of the coatings was investigated. The results indicated that all the AlCrN coatings exhibited a dense columnar microstructure. Higher charge voltage could facilitate a denser coating microstructure. As the charge voltage increased up to 450 V or higher, the microvoids along the column boundaries disappeared and the coatings became fully dense. The main phase in the AlCrN coatings was the c-(Al, Cr)N solid solution phase with NaCl-type phase structure. A diffraction peak of the h-AlN phase was detected at a 2θ of around 33°, when the charge voltage was higher than 500 V. The hardness of the AlCrN coatings varied as a function of charge voltage. The maximum value of the hardness (30.8 GPa) was obtained at 450 V. All the coatings showed good thermal stability and maintained their structure and mechanical properties unchanged up to 800 °C during vacuum annealing. However, further increasing the annealing temperature to 1000 °C resulted in apparent change in the microstructure and decrease in the hardness. The charge voltages also showed a significant influence on the high-temperature tribological behavior of the coatings. The coating deposited at the charge voltage of 550 V exhibited excellent tribological properties with a low friction coefficient.
Highlights
In the last few decades, both high-power impulse magnetron sputtering (HIPIMS) and high-power pulsed magnetron sputtering (HPPMS) technologies have attracted significant attention from researchers and industry [1]
As an alternative to the HIPIMS technique, the modulated pulsed power magnetron sputtering (MPPMS) technique has relatively lower peak power compared to HIPIMS and longer pulse lengths [5]
The coating unit was equipped with four sputtering cathodes, two of them with MPPMS power supply, and two with DC sputtering power
Summary
In the last few decades, both high-power impulse magnetron sputtering (HIPIMS) and high-power pulsed magnetron sputtering (HPPMS) technologies have attracted significant attention from researchers and industry [1]. The HIPIMS technique applies short power pulses, with power densities of up to several kilowatts per square centimeter, on to the cathode target, resulting in high ionization of the deposition species. This technique improves the coating structure, improves certain mechanical properties such as hardness and adhesion strength between the coating and the substrate, and can be used to obtain a uniform deposition on workpieces with a complex shape [2,3,4]. The microstructure, mechanical properties, thermal stability, and tribological properties of the coatings were investigated
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