Pack Mixture Research Articles

Codeposited Chromium‐Aluminide Coatings: I . Definition of the Codeposition Regimes

Aluminum and chromium were deposited simultaneously onto the nickel‐base alloy René 80 H using a pack‐cementation process. The pack mixtures contained a Cr‐Al source alloy and the activator salts tested were , , , and mixtures of and . Two deposition temperatures of 1100 and 1120°C were studied. Only aluminum deposited in packs activated by , only chromium deposited in packs activated by or , and both metals deposited simultaneously in packs activated by or mixtures containing no more than 2 weight percent (w/o) . The effects of varying the relative amounts of and in the mixed‐activator packs, together with the Cr‐Al alloy composition, on the type of coating obtained were also investigated. In all cases, the tendency to deposit chromium was related to the calculated equilibrium partial pressure ratio and the magnitude of . Codeposition of the two metals occurred when this ratio was between ca. 0.01 and 0.1. Adjustments to pack compositions were used to control chromium concentrations in the product coating, and a maximum chromium level of 25 w/o was achieved.

Improvement in Oxidation Resistance of TiAl by Preoxidation at 1200K in a Pack Mixture of Cr2O3 and Cr Powders

Improvement in Oxidation Resistance of TiAl by Preoxidation at 1200K in a Pack Mixture of Cr2O3 and Cr Powders

Corrosion behavior of low-carbon steel in ground water-basalt-bentonite mixtures at 250°C

The corrosion behavior of welded low-carbon steel under both aerated and deaerated conditions was studied as a function of packing material composition at 250°C with synthetic Grande Ronde basal ground water. Five packing mixtures, ranging from pure crushed Umtanum entablature basalt to pure Wyoming bentonite, were tested. Corrosion, as determined by weight loss, was lowest for 75 weight percent basalt/25 weight percent bentonite packing mixture under deaerated conditions and was lowest for 100 weight percent basalt under aerated conditions. Analysis of the weight loss data revealed that the majority of the data obeyed parabolic kinetics. Extrapolations of the kinetic data were made to 1,000 years, assuming both parabolic and linear kinetics. The parabolic kinetics yielded 0.064 mm (2.5 mil), while linear kinetics extrapolation resulted in 13 mm (approximately 1 2 inch) corrosion allowance for 1,000 years.