THE DEVELOPMENT AND SYNTHESIS OF MULTIFUNCTIONAL EROSION AND CORROSION RESISTANT TITANIUM-CHROMIUM-NITRIDE COATINGS FOR TURBOMACHINERY APPLICATIONS

Open Access
Author:
Reedy, Michael
Graduate Program:
Aerospace Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
None
Committee Members:
  • Douglas Edward Wolfe, Thesis Advisor
  • Michael Matthew Micci, Thesis Advisor
Keywords:
  • corrosion
  • TiCrN
  • erosion
  • cathodic arc
  • titanium chromium nitride
  • coating
  • characterization
Abstract:
Hard particle ingestion to aerojet engines is detrimental to metallic engine components, in particular, the rotating compressor blades. Thin TiN coatings have been applied to compressor components to mitigate erosion from hard particles. However, the TiN coatings deposited upon stainless steel components have created a galvanic coupling which leads to unsatisfactory corrosion performance. Chromium has been incorporated into the binary TiN system to create a ternary (Ti,Cr)N coating system to improve erosion and corrosion resistance. Cathodic arc deposition was used to deposit coatings using co-evaporation of a titanium and chromium cathode as well as evaporation of a titanium-chromium alloyed cathode. The coatings were characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and Vickers microhardness testing. In addition, the coating corrosion and erosion performance was analyzed. ASTM B117 corrosion testing was performed and the corrosion performance was largely dependent on the coating thickness and density. Nanolayered (Ti,Cr)N coatings deposited at low bias had the least corrosion resistance. Erosion testing was conducted in an in-house erosion rig at 30o and 90o critical impingement angles at particle velocities of 475 fps and 325 fps, respectively. Erosion performance decreased as the chromium composition was increased in the (Ti,Cr)N coatings. When chromium evaporator current was varied, the nanolayered (Ti,Cr)N coating erosion performance was bounded within TiN (upper limit) and CrN (lower limit) coating erosion performance. The nanolayered coatings possessed the erosion performance of both the binary TiN and CrN coatings and were dependent on the coating TiN / CrN phase volume. Nanolayered (Ti,Cr)N composite coatings deposited with low substrate bias values (-25 V, -50 V and -100 V) had improved erosion performance above the TiN coating. (Ti,Cr)N coatings deposited using a titanium-chromium alloyed source yielded monolithic single-phase (Ti,Cr)N coatings; however, analysis was limited due to processing issues. Finite element method (FEM) leading edge deformation modeling of a GE T58 first-stage compressor blade showed that particle velocity was more detrimental than particle size, and horizontal and vertical displacement values varied with particle impingement angle. Select results will be presented.