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The deposition of sodium sulfate from flames containing sodium W and sulfur is regarded as one of the fundamental steps in the phenomenon of "hot corrosion" of turbine components. Recently, a local thermochemical equilibrium (LTCE) method of predicting condensation temperatures of sodium sulfate in flame environments was described. This paper presents results of an experimental study to test the validity of the theoretical dew point predictions and to provide the basis for'developing a deposition rate theory. Experiments were run in a Mach 0.3 atmospheric_ pressure laboratory burner rig.. Flames were doped with sea salt, Na2SO 41 and NaCl, respectively. Deposits were collected on cylindrical platinum targets placed in the combustion products, and the deposition was studied as a function of collector temperature .. Experimental deposition onset temperatures checked within experimental error with LTCE-predicted temperatures. A multicoinponent mass transfer equation was developed to predict the rate of deposition of Na2SO4(c) via vapor transport at temperatures below the deposition onset temperature. The phenomena of species transport by simultaneous Fick diffusion, Soret (thermal) diffusion, convection and turbulence are included, sub i ject to the basic assumption that no reaction or phase change occur STAR Category 26 i _j

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04Compositions in the tantalum-carbon system were prepared by carburizing high-purity tantalum wires. T h e microstructures so produced exhibit regions of a characteristic striated structure identical to those observed by earlier investigators. There are disparities in the literature as to the origin of such structures in the tantalum-carbon system. They have been variously described as "twins," "striated structure," "precipitate," and' "structure of unknown origin." This paper presents conclusive evidence that the structures in question are the result of precipitation on cooling. I n addition, a coherent precipitation model is applied in which it is shown that the lattice relationship { 0 0 0 1 )~~, c~~( 1 1 1 }~~~ can exist with less than 0.5% misfit. This relationship is shown to completely explain the

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