FLUIDIZED BED TECHNIQUES FOR COATING REFRACTORY METALS.
Abstract
This report describes the development of fluidized bed techniques for applying protective coatings to refractory alloys by three coating processes: simple disilicide on C-129Y columbium alloy, vanadium-modified disilicide on C-129Y columbium alloy and Ta-10W tantalum alloy, and (chromium-titanium)-silicon on Cb-752 and FS-85 columbium alloys. The simple disilicide process was optimized in an 8-inch fluidized bed and scaled-up in an 18-inch fluidized bed using statistically planned experiments to determine the effects of significant variables. Cost saving measures successfully applied in the simple disilicide scale-up were: silicon conditioning by air injection, recycling of the fluidizing gas, and higher operating temperatures. The process was production proofed by coating typical production size hardware of C-129Y alloy in the 18-inch fluidized bed. A fluidized bed process for applying the vanadium-modified disilicide coating was developed in a 4-inch fluidized bed and scaled-up in an 8-inch fluidized bed. The three-step coating process, consisting of pre-siliconizing, vanadizing and post-siliconizing, exhibited good process reproducibility. The vanadium-modified coating on C-129Y columbium alloy displayed a three-fold increase in cyclic oxidation life at 2600 degrees F compared to the optimized simple disilicide coating on C-129Y. A two-step fluidized bed process, consisting of Cr-Ti co-deposition and siliconizing, was developed for applying the (Cr-Ti)-Si coating to columbium alloys.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1967
- Accession Number
- AD0818536
Entities
People
- Dale W. Martin
- James C. Goodwin
- Ronald T. Torgerson
- Walter Batiuk
Organizations
- Boeing