Application of sinter -hardenable materials for advanced automotive applications such as gears, cams and sprockets

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Application of sinter -hardenable materials for advanced automotive applications such as gears, cams and sprockets

Baran, M.C. / Winterton, P.J. / Haberberger, T.E. / Cornelio, T.J.

Sinter-hardening materials have offered acceptable apparent hardness but at the expense of mechanical properties and sintered density. When conventional sintering temperatures (1140 deg C) are coupled with accelerated cooling, an Ancorsteel 737 SH premix containing 1 w/o copper + 0.7 w/o graphite was found to provide the best combination of tensile properties and apparent hardness. When carbon levels were increased beyond 0.7 w/o, a decrease in strength was observed due to the formation of retained austenite. Hence, under the production conditions considered, 2 w/o copper + 0.9 w/o graphite specimens exhibited lower tensile and yield strengths than 1 w/o copper + 0.7 w/o graphite specimens. Sinter-hardening was achieved by high temperature sintering (1260 deg C) Ancorsteel 737 SH premixes containing either graphite and copper or graphite and nickel. However, as a consequence of slow cooling rates, copper or nickel additions were imperative to achieving an acceptable sinter-hardening response. Lowering graphite additions from 0.9 w/o to 0.7 w/o in the presence of 2 w/o copper caused an increase in both strength and ductility. Although a mixed effect was observed in a 2 w/o nickel mix, higher ductility resulted when graphite was reduced from 0.9 w/o to 0.7 w/o.