NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Flame Spray Strain Gages with Improved Durability and LifetimesThe focus of this APP research program was to improve the bond coats used in the fabrication of flame sprayed instrumentation. Typically. a bond coat is applied to a superalloy surface prior to the application of a thin dielectric coating onto which instrumentation is placed. After affixing the instrumentation, a much thicker ceramic topcoat is typically applied to protect the instrumentation from harsh environments. The fatigue life of NiCoCrAlY coated superalloys was extended beyond current state-of-the-art by relatively simple and cost effective means. Heat treatment in reduced oxygen partial pressures at 1750 to 1800 F effectively doubled the fatigue life of NiCoCrAlY coated substrates relative to as-sprayed substrates and when used in conjunction with platinum diffusion barriers yielded a four fold increase in the fatigue life of NiCoCrAlY coated substrates. Further improvements in the fatigue life of thermally sprayed coatings were made by employing intermediate coatings, which minimized thermal expansion differences between the bond coat and top coat. Combinatorial chemistry experiments yielded an optimum composition for an intermediate TCE matching coating that showed considerable promise in extending the fatigue life of thermal spray instrumentation. The intermediate coating had two functions: to reduce the surface roughness of the peaks and valleys associated with the as-sprayed NiCoCrAlY bond coat, and to produce a thin layer of a mixture of Al2O3 and NiCoCrAlY that exhibited an intermediate TCE. The optimal composition of the intermediate coating consisted of 60 wt% Al2O3 and 40 wt% NiCoCrAlY, as determined by energy dispersive analysis of x-rays (EDS). Intermediate coatings having this composition were prepared by physical vapor deposition and the resulting coating systems are being evaluated in our test facility.
Document ID
20030055628
Document Type
Contractor Report (CR)
Authors
Fralick, Gustave (NASA Glenn Research Center Cleveland, OH, United States)
Gregory, Otto (Rhode Island Univ. Narragansett, RI, United States)
Date Acquired
September 7, 2013
Publication Date
April 1, 2003
Subject Category
Instrumentation and Photography
Report/Patent Number
NAS 1.26:212210
E-13818
NASA/CR-2003-212210
Funding Number(s)
WORK_UNIT: WU 708-87-23
CONTRACT_GRANT: NAG3-2652
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

Available Downloads

NameType 20030055628.pdf STI