With steam temperature of central-station boiler plants advancing to 1050 F in new installations today, and with indications that steam temperatures of 1200 F are not too far in the future, selection of suitable materials for superheater and reheater tubing requires special consideration. Alloys having good service characteristics in the range of 1100 F to 1350 F are required to meet the foregoing steam conditions. While mechanical properties of such alloys are not too serious a problem, the matter of corrosion resistance is a critical one. The ASME Special Research Committee on High-Temperature Steam Generation, recognizing the importance and the complexity of the corrosion problems, undertook sponsorship of a comprehensive program to evaluate commercially available alloys for suitability as superheater and reheater tubing at metal temperatures up to 1350 F. (The program is divided into two broad parts.) One is concerned with the reaction of high-pressure high-temperature steam on such materials. The other deals with corrosion by flue gases and slag-forming ash on the external surface of the tubing, and is divided in turn into two phases. The specific objective of one phase is the evaluation of the alloys with respect to resistance toward corrosion by the combustion products of the various fuels used for boilers, under actual field conditions. The objective of the other phase, carried out in the laboratory, is the investigation of the effect of certain components of a combustion atmosphere on the rate of corrosion of the same alloys. This paper is concerned with the field-test phase of the program which was carried out at Battelle. The laboratory work done at Battelle will be the subject of a future paper.

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