In Geo-Coat project, laboratory-based tests in simulated geothermal conditions have been performed. Corrosion resistance, erosion wear, erosion-corrosion wear, sliding wear, contact angle and cost performance have been evaluated for each material/substrate combination selected for the project. Systems prepared (i.e. deposited and manufactured for coatings and MMCs respectively) on each substrate have then been scored and ranked together with the state-of-the-art wrought alloy currently employed for the specific application.

Application Area ID Application Areas Coating Selected By The Project Coating Composition (Mol. Ratio) Coating Composition (wt.%) Deposition/Consolidation Process
S1 Pipes & Casings LC_HEA2 CoCrFeNiMo 0.85 (HEA2) Co19.19 Cr19.19 Fe19.19 Ni19.19 Mo26.56 Laser Cladding (LC)
S2 Valve stem/turbine (blades) LC_HEA2 CoCrFeNiMo 0.85 (HEA2) Co19.19 Cr19.19 Fe19.19 Ni19.19 Mo26.56 Laser Cladding (LC)
S3 Turbine rotors (+diaphragms) LC_HEA2 CoCrFeNiMo 0.85 (HEA2) Co19.19 Cr19.19 Fe19.19 Ni19.19 Mo26.56 Laser Cladding (LC)
S4 Turbine blades LC_HEA2 CoCrFeNiMo 0.85 (HEA2) Co19.19 Cr19.19 Fe19.19 Ni19.19 Mo26.56 Laser Cladding (LC)
S5 Pump impellers HIP_Ti64+10%TiB₂ - Ti6AI4V 90 TiB₂10 Hot Isostatic Pressing (HIP)
S6 Heat exchanger tubes ENP_LP (Low Phosphorus) Ni-P/Ni-P-PTFE - Electroless Nickel Plating (ENP)

This table illustrates the coating system ranking for Turbine blades

Application area SOA/Coating types Corrosion and erosion Mechanical and tribological
Erosion-corrosion Corrosion penetration (max.μm) Stress corrosion cracking (SCC) Permeability Pitting Cracks Erosion-wear 3PB tilt angle (°) Wear rate Coefficient of friction (CoF) Nano-hardness Adhesion
(mm/y) Flow through corrosion (7 days) Static corrosion (60 days) (g/min) Pre-corr. Post-corr. x10³ mm³ N⁻¹ m⁻¹ (-) (HV) (N)
S4 Grade 304L N/A 0.1 0.1 N/A - + - N/A N/A N/A 2.56 0.8 414 N/A
S4 LC_HEA2 N/A 0.5 N/A N/A - - - N/A N/A N/A 1.74 0.46 N/A -
S4 LC_HEA5 N/A N/A 205* - + - + 0.136 13 12 7.53 0.82 263 >200
S4 HVOF_CA2 N/A 30 110 N/A - - + 0.063 14 13 0.26 0.52 1208 65
  • + : corrosion damage is present
  • - : corrosion damage is NOT present
  • N/A : not relevant or test not performed.
  • * : max. depth of crack.
  • ** : through the thickness of the coating
  • HVOF : High Velocity Oxygen Flow
  • CA2 : C9.5CrbalNi20 Cermet

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