Development of Coatings for Corrosion/Erosion Protection of Internal Components of Coal Gasification Vessels. Volume II. Furnace Fused MCrAl Coatings

摘要

This report presents the results of a program of research to develop and evaluate sulfidation-resistant MCrAl coatings for use on stainless steel and superalloy components of coal gasification process equipment. It is concerned with the development and evaluation of MCrAl coatings (where M is Fe, Ni, Co) which are produced by melting and alloying coating powders on the surface of high temperature alloy substrates in a vacuum furnace. It was found that 33Co-67Al and 33Cr-63A1-4Hf prealloyed powder mixtures fused into the surface of alloy 800 produced coatings that survived 2000 h at 1800 exp 0 F (1255 exp 0 K) in a low Btu coal gasification atmosphere with 1% H sub 2 S. The addition of refractory sulfide formers such as Ti, Cb, and Mo in the CrAlHf composition reduced resistance to oxidation and shortened coating life. The best coating is 33Cr-63Al-4Hf on alloy 800. Detailed procedures for application of the coating are given and the effect of the coating and subsequent long time exposure to high sulfur low Btu coal gasification atmospheres on mechanical properties of the substrate are discussed. Factors that control performance and overall coating life are reviewed and recommendations for further development and evaluation of the coating are presented. 35 figures, 24 tables. (ERA citation 06:028034)