CrN, AlCrN And AlCrSiN Coatings Deposited By High Power Impulse Magnetron Sputtering

PVD hard coatings have been widely used to improve the properties of cutting tools. Generally, there are two means available for the preparation PVD hard coatings, namely, magnetron sputtering (MS) and arc ion plating (AIP). AIP can acquire high ionization rate plasma source which can contribute to the hardness and adhesion of the coatings. However, the micro-droplets due to the arc process causes the high surface roughness, resulting in high friction coefficient and wear rate. MS, espcially direct current MS (DCMS) can acquire the coatings with smooth surface, but the coating hardness and adhesion are not high due to low ionization rate. High Power Impulse Magnetron Sputtering (HIPIMS) can significantly increase the ionization rate and energy of the species for the growth coatings as compared to DCMS. In addition, the micro-droplets are absent during the deposition process. Accordingly, HIPIMS has been respected to be one of the best techniques to prepare hard coatings.In this paper, CrN, AlCrN and AlCrSiN coatings were deposited by HIPIMS with different substrate bias voltages and frequencies. The composition, structure, mechanical properties of the coatings were studied using Energy Disperse Spectroscopy, Scanning Electronic Microscopy, X-Ray diffraction, nanoindentation and so on. The main conclusions are as follows.(1) CrN coatings:as the substrate bias voltage increased, the width of columnar crystal decreased. When the bias voltage reached to -200V, there was no obvious columnar crystal and the coating surface presented a crater-like feature. At relatively low bias volage (≤-100 V), the diffraction peak of CrN(200) was very strong. However, when the bias voltage increased (-150 V and -200 V). The main diffraction peak became wide. As the substrate bias voltages increased, the hardness, young’s modulus and residual stress of the coatings increased, and reached the maximum value at -150V. The CrN coating exhibited good adhesion. The friction coefficients of the coatings was 0.5-0.75.(2) AlCrN coatings:With increasing the substrate bias voltage, the width of columnar crystal was decreasing firstly and then increasing. The preferred orientations were CrN(111), CrN(200) and CrN(220). Hardness, young’s modulus and residual stress are gradually increasing with increasing the substrate bias voltage, and reach maximum at-100 V and-150 V.(3) AlCrSiN coatings:In different substrate bias voltages and frequencies, Si content of AlCrSiN are all over 13% and almost all of them are the amorphous state of crystal. Hardness, young’s modulus and residual stress are and gradually increased with the increase of the substrate bias voltages. Different frequencies of AlCrSiN are compressive stress, with the increase of frequency, residual stress firstly increases and then gradually decrease.The influence of frequency to coating hardness is no rule. AlCrSiN showed poor in the binding force.