Wear Resistance of Powder Hard Metal Inserted Ductile Iron
A continuous effort is being devoted to study the feasibility of improving the wear resistance of ductile iron components through an insertion of a hard metal powder layer during the casting process. Tests have been run to evaluate the wear resistance of the inserted material, compared to a non inserted ductile iron. The tests have been run in accordance with ASTM G65-94, which specifies the so-called rubber wheel test. Three different kinds of material have been tested: a non inserted ductile iron, an inserted ductile iron in the as-cast state and an inserted ductile iron with a rectified surface. The tests have been run gradually; each test piece has been taken out from the test apparatus and weighted at different intervals, from 200 to 6400 wheel revolutions (or 0.1 to 4.4 km of sliding distance); the results obtained show that the non inserted ductile iron presents a loss of weight fifty percent higher than the inserted material. The analysis of the surface of the test pieces after the wear tests has been run under stereo and scanning electron microscopy. The non inserted ductile iron test piece surface has shown an uniform waviness with a wavelength around half a millimeter and under higher magnification much finer wear marks have been observed. The inserted ductile iron test piece surface has shown the same relief with half a millimeter wavelength but a significant difference has been noticed: the fine wear marks have been observed in the metallic matrix of the insert but they stop in the neighborhood of the tungsten carbide particles, leading the authors to propose that these hard particles remained unchanged until the metallic matrix supporting them has been sufficiently removed to cause the respective extraction; this behavior should explain the smaller weight loss rate of the inserted material.
Paula Maria Vilarinho
N. Lourenço and H. Santos, "Wear Resistance of Powder Hard Metal Inserted Ductile Iron", Materials Science Forum, Vols. 514-516, pp. 784-788, 2006