The Influence of Austempering Temperature on the Wear Resistance of Ductile Iron under Two Different Tribosystems

Abstract

This paper reports the results obtained in a research conducted to evaluate austempered ductile iron(ADI) as a wear resistant material for the production of machine parts processed at intermediate and highaustempering temperatures (Ta). Severe abrasion in actual service performance trials and low stress abra-sion laboratory tests (ASTM G-65) were carried out along with microstructural characterization by optical mi-croscopy and X-ray diffraction. The results derived show that ADI yields excellent abrasion resistance underthe operating conditions resulting from the field tests when Ta is raised. Nevertheless, ADI show an oppo-site trend under the low stress abrasion conditions imposed by the dry sand/rubber wheel abrasion appara-tus (ASTM G-65). The presence of a metastable and ductile ausferrite phase (reacted and unreacted austen-ite ferrite) in ADI microstructure appears to be the most relevant factor influencing the performance ob-served. In addition to a high deformation capability detected at the wear surfaces, an austenite to marten-site transformation took place as determined by X-ray diffraction. These two factors combined make theausferritic microstructure overcome hardness reduction when the austempering temperature is raised, im-proving or sustaining the resistance to severe abrasive wear but, at the same time, increasing impact tough-ness.