General Description Dura-Bar Ni-Resist irons contain an austenitic matrix of approximately 10% alloy carbides. The austenitic structure is suitable for corrosive environments in sour well oils, salts, salt water acids and alkalies. The iron is relatively soft and chrome is added to produce carbides that help improve wear resistance. Ni-Resist is denser than gray or ductile irons and has a higher coefficient of thermal expansion. Dura-Bar Type 1 Ni-Resist is manufactured to produce a material conforming to ASTM A436.
Microstructure  | CENTER AREA
100x, etched in 5% Nitol |  | EDGE AREA
100x, etched in 5% Nitol |  | |
The microstructure will consist of Type VII, A, size 4-6 graphite as defined in ASTM A247. The matrix will be austenite with 5-10% alloy carbide. The rim will contain Type D graphite, size 6-8. Chill carbides are less than 5% in any field at 100x and will be well dispersed.
Heat Treat Response Austenitic alloys cannot be hardened by heat treatment. They may be softened and homogenized by heating to 1800-1900° F (980-1040° C) for three to five hours and air-cooling. This breaks down some of the carbides and most of those remaining will be sphereoidized. Anneal softens the material without detrimental effect on the strength properties. Type 1 Ni-Resist should not be used in applications involving service above 1300° F (430° C).
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