Some observations of the influence of δ-ferrite content on the hardness,galling resistance,and fracture toughness of selected commercially available iron-based hardfacing alloys |
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Authors: | B V Cockeram |
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Affiliation: | (1) the Bechtel Bettis Atomic Power Laboratory, 15122-0079 West Mifflin, PA |
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Abstract: | Iron-based weld hardfacing deposits are used to provide a wear-resistant surface for a structural base material. Iron-based
hardfacing alloys that are resistant to corrosion in oxygenated aqueous environments contain high levels of chromium and carbon,
which results in a dendritic microstructure with a high volume fraction of interdendrite carbides which provide the needed
wear resistance. The ferrite content of the dendrites depends on the nickel content and base composition of the iron-based
hardfacing alloy. The amount of ferrite in the dendrites is shown to have a significant influence on the hardness and galling
wear resistance, as determined using ASTM G98 methods. Fracture-toughness (K
IC) testing in accordance with ASTM E399 methods was used to quantify the damage tolerance of various iron-based hardfacing
alloys. Fractographic and microstructure examinations were used to determine the influence of microstructure on the wear resistance
and fracture toughness of the iron-based hardfacing alloys. A crack-bridging toughening model was shown to describe the influence
of ferrite content on the fracture toughness. A higher ferrite content in the dendrites of an iron-based hardfacing alloy
reduces the tendency for plastic stretching and necking of the dendrites, which results in improved wear resistance, high
hardness, and lower fracture-toughness values. A NOREM 02 hardfacing alloy has the most-optimum ferrite content, which results
in the most-desired balance of galling resistance and high K
IC values. |
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Keywords: | |
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