Effect of microstructure on the erosion resistance of Cr-Si-N coatings

Erosion by solid particle impact can cause severe damage to critical components of airplanes, helicopters and other systems, thus affecting their overall performance, cost and most notably safety. In our search for novel high performance erosion resistant coatings, we studied Cr-Si-N coatings (8 to 13 mu m thick) deposited on AISI 410 stainless steel substrates by DC reactive dual-magnetron sputtering using Cr and Si targets. Microstructure, composition and the mechanical properties were studied as a function of the silicon content (C-si) using XRD, ERD-TOF, and the depth sensing and Vickers indentation techniques. A maximum hardness of 26.6 GPa was found for Cr-Si-N with C-si= 6.7 at.%, while that of pure CrN was 19.4 GPa. Solid particle erosion (SPE) tests were performed according to the ASTM G76 standard on a test rig developed by our laboratory: Al2O3 particles with an average diameter of 50 mu m were projected onto the coating surface, with a mean velocity of 70 m/s and a normal (90 degrees) incidence angle. The 90 degrees erosion rate of Cr-Si-N with C-si = 11.6 at.% was found to be 5.2 x 10(-3) mg/g, one order of magnitude lower than that of pure CrN and 20 times lower than that of the substrate. We specifically discuss the SPE behavior of the Cr-Si-N coatings with respect to their mechanical (hardness, reduced Young's modulus and toughness) and microstructural (texture and morphology) characteristics. (C) 2008 Elsevier B.V. All rights reserved.