Mechanical Behavior of Alloy 800 at 838 K
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INTRODUCTION
A L L O Y 800 is an Fe-based austenitic alloy containing 30 to 35 pct Ni and 19 to 23 pct Cr. The material was developed in 1949 to be a less expensive alternative to nickel-based alloys for applications in which more corrosion resistance was required at elevated temperatures than could be provided by 300-series stainless steels. The alloy has been extensively utilized in this type of application since that time. 1For example, Alloy 800 has an excellent service record as a tubing material in petrochemical processing plants at temperatures up to 1250 K. More recently, this alloy has been used as a superheater/ reheater tubing material for water/steam systems in reactor power plants, an application which requires good creep strength in addition to corrosion resistance. To meet this added requirement, a modified alloy specification, 800H, was developed. Whereas Alloy 800 can have any carbon content up to 0.10 pct, Alloy 800H must have 0.05 15 hours) would have differed greatly had the material received a mill anneal treatment. All of the M23C6 would have likely been in the form of larger particles, many on grain boundaries; there would have been no fine, intragranular M23C6 formed during cycling. In addition, Figure 15 shows that the mill anneal might leave insufficient Ti for y ' to form, moving this heat out of the two phase field. METALLURGICALTRANSACTIONS A
1100
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1000
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