Abstract
The high-power impulse magnetron sputtering (HiPIMS) technique is widely used owing to the high degree of ionization and the ability to synthesize high-quality coatings with a dense structure and smooth morphology. However, limited efforts have been made in the deposition of MAX phase coatings through HiPIMS compared with direct current magnetron sputtering (DCMS), and tailoring of the coatings’ properties by process parameters such as pulse width and frequency is lacking. In this study, the Cr2AlC MAX phase coatings are deposited through HiPIMS on network structured TiBw/Ti6Al4V composite. A comparative study was made to investigate the effect of average power by varying frequency (1.2–1.6 kHz) and pulse width (20–60 μs) on the deposition rate, microstructure, crystal orientation, and current waveforms of Cr2AlC MAX phase coatings. X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM) were used to characterize the deposited coatings. The influence of pulse width was more profound than the frequency in increasing the average power of HiPIMS. The XRD results showed that ex situ annealing converted amorphous Cr-Al-C coatings into polycrystalline Cr2AlC MAX phase. It was noticed that the deposition rate, gas temperature, and roughness of Cr2AlC coatings depend on the average power, and the deposition rate increased from 16.5 to 56.3 nm/min. Moreover, the Cr2AlC MAX phase coatings produced by HiPIMS exhibits the improved hardness and modulus of 19.7 GPa and 286 GPa, with excellent fracture toughness and wear resistance because of dense and column-free morphology as the main characteristic.
Highlights
Among lightweight materials, titanium matrix composites (TMCs) are suitable candidates in automotive, aerospace, and military applications because of their excellent combination of mechanical properties and wear resistance [1]
Cr2 AlC coatings were prepared at different combinations of frequency and pulse width at constant discharge voltage and duty cycle, which results in variable average power (Pave ) depending on plasma characteristics
It is worth noting that the discharge current waveform at different parameters in high-power impulse magnetron sputtering (HiPIMS) is of utmost importance to determine plasma characteristics and deposited coatings’ properties
Summary
Titanium matrix composites (TMCs) are suitable candidates in automotive, aerospace, and military applications because of their excellent combination of mechanical properties and wear resistance [1]. The TiBw/Ti6Al4V composite is a type of discontinuously reinforced titanium matrix composite (DRTMC), in which reinforcement of TiB-whiskers (TiBw) was formed around the matrix of Ti6Al4V particles, forming a 3D quasi-continuous network architecture [2]. Because of this novel structure, TiBw/Ti6Al4V composite possesses superior isotropic properties to its counterpart, monolithic Ti-6Al-4V alloy [3]. TiBw/Ti64 composite shows superior mechanical properties at temperatures of 500–600 ◦ C, but poor oxidation resistance due to the formation of unprotected TiO2 scale above the restricted temperature range [8,9]. Protective MAX phase films could play their part to enhance its oxidation and wear resistance further in the harsh environment
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