Evaluation of the mechanical properties of CrAlN coatings deposited on WC[sbnd]Co substrates in a magnetron discharge: Experiment and modeling

The enhancement of cutting tools’ performance by properly engineering their surfaces is one of the most demanded fields of applications for plasma-based coating deposition methods. While tungsten carbide (WC[sbnd]Co) cutting tools are usually processed by chemical vapor deposition techniques, their treatment by magnetron sputtering-based physical vapor deposition is promising since it allows one to fine-tune the surface properties by controlling the charged particle flux onto the surface. In this work, the mechanical properties (hardness and Young's modulus) were studied for the CrAlN coatings deposited onto WC[sbnd]Co (P10) substrates in a pulsed DC magnetron discharge. The discharge was operated in reactive mode by sputtering of Cr and Al targets in the Ar/N₂ atmosphere, and the ratio of Cr/Al discharge power values was selected to optimize the Al content in the resulting films. The bias voltage applied to the samples during the deposition was varied from –100 V to +100 V with respect to the grounded anode. The coatings were studied by means of scanning electron microscopy, X-ray diffraction, nano- and microindentation. The results show the improvement in surface hardness up to 28 GPa for the CrAlN coatings fabricated at –100 V bias voltage, with Young's modulus lower than the substrate's for all studied deposition modes. The deformation behavior of coatings during the indentation tests was additionally investigated using a finite element modeling approach, and the simulated load-displacement curves are in good agreement with the experimentally measured curves. Both experiments and simulations demonstrate that CrAlN coatings are plastically deformed during indentation with the absence of cracking behavior.