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Plasma spray of Nichrome matrix composite contains dispersed glass for oxidation protection and calcium fluoride for lubrication. Coatings can be applied to bearing journals and bearing bores. Coating was easily machinable and had excellent bond strength on substrate metal.
An experimental program in which salt-spray-exposed coatings have been irradiated is described and discussed.
Several plasma-sprayed coating systems were evaluated for structural stability in hydrogen plasma and in oxygen plasma mixed with hydrogen plasma. The principal test heat flux was 15 Btu per inch squared seconds. The system consisted of a number of thin 0.002 to 0.020 in. layers of metal oxides and/or metals. The principal materials included are molybdenum nichrome, alumina, and zirconia. The study identifies important factors in coating system fabrication and describes the durability of the coating systems in the test environments. Values of effective thermal conductivity for some of the systems are indicated.
A test program was conducted with duPont duplicating film type SR 112 and SCOLOR developer and Kodak duplicating film types 2430, 2422, and FE 2628 (SO-467) and MX-641 developer to determine sensitometric and image quality characteristics of these materials when used with a fultron spray processor. The test results show that the SCOLOR developer foams excessively in the fultron processor when used with or without the addition of an antifoaming agent. The Kodak type FE 2628 film with MX-641 chemistry had the longest linear Log E range at a 1.0 gamma. Sensitometric curves and granularity traces for all film process combinations tested are included.
A plasma-sprayed coating is described with good lubricating properties over a wide temperature range. The coating, designated NASA LUBE PS101, contains silver, nichrome, calcium fluoride, and an oxidation protective glass. Oscillating tests were conducted of self-aligning, plain cylindrical bearings, in which the bore was lined with 0.025 cm (0.010 in.) thick coatings of PS101; these were conducted at a radial load of 3.5 x 10 to the 7th power N/sq m (5000 psi) in nitrogen gas at -107 C (-160 F), in vacuum at room temperature, and in air from room temperature to 870 C (1600 F). Friction coefficients were less than 0.25 in all cases and wear rates were low. The coating is not brittle, and it has adequate oxidation resistance in air to at least 870 C.
The approach described makes use of high-speed photography employing short-duration light sources. Drops are photographed in flight as they pass through a narrow slice of the spray on which the optical system is focussed. Two sparks fired at intervals of a few microseconds give double image photographs of drops. Drop velocity is calculated by measuring the distance between the two images of the drop and the time interval between sparks. Details regarding the optical and photographic system are described along with the design of the electronics system.
A high pressure water blast with rotating spray bar treatment for removing paint and rubber deposits from airport runways is studied. The results of the evaluation suggest that the treatment is very effective in removing above surface paint and rubber deposits to the point that pavement skid resistance is restored to trafficked but uncontaminated runway surface skid resistance levels. Aircraft operating problems created by runway slipperiness are reviewed along with an assessment of the contributions that pavement surface treatments, surface weathering, traffic polishing, and rubber deposits make in creating or alleviating runway slipperiness. The results suggest that conventional surface treatments for both portland cement and asphaltic concrete runways are extremely vulnerable to rubber deposit accretions which can produce runway slipperiness conditions for aircraft operations as or more slippery than many snow and ice-covered runway conditions. Pavement grooving surface treatments are shown to be the least vulnerable to rubber deposits accretion and traffic polishing of the surface treatments examined.
A chemical spray process for the production of thin film CdS-Cu2S solar cells is discussed that is projected to cost less than $60/kW in very large scale production. The average efficiency of these cells has been improved from less than 0.3% in 1971 about 4.5% at present. Further developments for the process are considered to raise the efficiency, and to attain long life stability.
Experiments were conducted in a ground based vacuum chamber to determine physical properties of water-ice in a space-like environment. Additional ices, alcohol and ammonia, were also studied. An analytical analysis based on the conservation of angular momentum, resulted in despin performance parameters, i.e., total water mass requirements and despin times. The despin and retrieval of a disabled spacecraft was considered to illustrate a potential application of the water spray technique.
Tubing and trigger assembly directs aerosol spray into hard-to-reach areas.
A scanning radiometer was used to determine the effect of airstream velocity on the mean drop diameter of water sprays produced by pressure atomizing and air atomizing fuel nozzles used in previous combustion studies. Increasing airstream velocity from 23 to 53.4 meters per second reduced the Sauter mean diameter by approximately 50 percent with both types of fuel nozzles. The use of a sonic cup attached to the tip of an air assist nozzle reduced the Sauter mean diameter by approximately 40 percent. Test conditions included airstream velocities of 23 to 53.4 meters per second at 293 K and atmospheric pressure.
A scanning radiometer was used to determine the effect of airstream velocity on the mean drop diameter of water sprays produced by pressure atomizing and air atomizing fuel nozzles used in previous combustion studies. Increasing airstream velocity from 23 to 53.4 meters per second reduced the Sauter mean diameter by approximately 50 percent with both types of fuel nozzles. The use of a sonic cup attached to the tip of an air assist nozzle reduced the Sauter mean diameter by approximately 40 percent. Test conditions included airstream velocities of 23 to 53.4 meters per second at 293 K and atmospheric pressure.
Silicon tetrachloride spray feeder mechanism is incorporated into high-temperature reactor for production of highly pure silicon intended for solar cells. Feeder supplies silicon tetrachloride as liquid droplets that rapidly vaporize in high temperature (2,000 to 2,200 K) reactor zone.
Fixture that rotates about two axes ensures uniform coating and minimizes handling of coated workpiece. Each side of tile is coated in sequence by moving turntables until surface is perpendicular to spray. Process is repeated until desired thickness has built up.
A ceramic seal system is reported that employs plasma-sprayed graded metal/ceramic yttria stabilized zirconium oxide (YSZ). The performance characteristics of several YSZ configurations were determined through rig testing for thermal shock resistance, abradability, and erosion resistance. Results indicate that this type of sealing system offers the potential to meet operating requirements of future gas turbine engines.
Self-lubricating, multicomponent coatings, which lubricate over a wide range of operating conditions, are described. The coatings were successfully applied by plasma-spraying mixed powders onto superalloy substrates. They were evaluated in friction and wear experiments, and in sliding contact bearing tests. These coatings are wear resistant by virtue of their self lubricating characteristics rather than because of extreme hardness; a further benefit is low friction. Experiments with simple pin on disk sliding specimens and oscillating plain cylindrical bearing tests were performed to evaluate the tribological properties of the coatings. It was shown that coatings of nichrome, glass and calcium fluoride are self-lubricating from about 500 to 900 C, but give high friction at the lower temperatures. The addition of silver to the coating composition improved the low temperature bearing properties and resulted in coatings which are self-lubricating from cryogenic temperatures to at least 870 C; they are therefore, wide temperature spectrum, self-lubricating compositions.
A research gas turbine combustor was operated under realistic conditions such that the influence of individual variables (in particular, fuel spray characteristics) on emissions could be determined. The special combustor allows independent control over drop size, fuel-air ratio, air inlet temperature, pressure, reference velocity, and residence time. Also, it lends itself to theoretical modeling and turbulent intensity measurements through use of laser velocimetry. Emission results for a range of operations are presented. A number of graphs show which show the variations of emissions levels with one variable at a time are included. In every case, the fuel is jet A, the pressure is atmospheric, and combustion is limited to a primary zone.
A method for preparing composite powders of the three coating components was developed and a procedure that can be used in applying uniform coatings of the composite powders was demonstrated. Composite powders were prepared by adjusting particle sizes of the components and employing a small amount of monoaluminum phosphate as an inorganic binder. Quantitative microscopy (image analysis) was found to be a convenient method of characterizing the composition of the multiphase plasma-sprayed coatings. Area percentages and distribution of the components were readily obtained by this method. The adhesive strength of the coating to a nickel-chromium alloy substrate was increased by about 40 percent by a heat treatment of 20 hours at 650 C.