NS-4 Coating Process Development for Columbium Alloy Airfoils.
Final rept. Apr 74-Feb 76,
SOLAR SAN DIEGO CALIF
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The excellent potential of the Solar NS-4 coating for protecting columbium alloy turbine vanes up to 1371C was demonstrated. Procedures were developed to coat both internal and external surfaces of configurations representative of turbine vanes. With spray application of the modifier the NS-4 process is a two-cycle coating with a W-Mo-V-Ti modifier applied first and vacuum sintered followed by pack siliciding consistent 500-hour protection at 1371C was obtained on external radii as small as 0.25 mm. Coating of internal surfaces by dipping was not reliable but many specimens survived 500 hours of cyclic exposure. Tests of coated 15-degree wedges in an oxidationerosion rig showed no failures after 500 severe thermal cycles between 260C and 1371C. A number of cast hollow single vane segments were successfully coated and oxidation exposed one hour at 1371C. Appearance was excellent. Several problem areas that need additional investigation were elucidated, viz, coating of internal surfaces and temperature gradient induced coating stresses.
- Coatings, Colorants and Finishes
- Jet and Gas Turbine Engines