Title: Sinter hardening of low-alloy steels: influence of part geometry and physical properties of the material

Authors: Gian Filippo Bocchini, Maria Rosa Pinasco, Barbara Rivolta, Giuseppe Silva, Enrica Stagno

Addresses: Powder Metallurgy Consultant, 16035, Rapallo, Via Vespucci, 48/18 (GE), Italy. ' Dipartimento di Chimica e Chimica Industriale, Universita di Genova, Via Dodecaneso, 32, 16046 Genova, Italy. ' Dipartimento di Meccanica, Politecnico di Milano, Polo Regionale di Lecco, Via M. d'Oggiono 18a, 23900 Lecco (LC), Italy. ' Dipartimento di Meccanica, Politecnico di Milano, Polo Regionale di Lecco, Via M. d'Oggiono 18a, 23900 Lecco (LC), Italy. ' Dipartimento di Chimica e Chimica Industriale, Universita di Genova, Via Dodecaneso 32, 16046 Genova, Italy

Abstract: Assuming that the cooling rate of parts depends on thermal conductivity of the material and on the surface/volume ratio, a two-ways study has been carried out. Firstly, the isothermal surfaces have been calculated by a numerical method on parallelepipeds of constant cross section and varying height and weight. Microstructures, depending on isothermal surfaces predicted by the numerical model, agree with microhardness and mechanical properties. A maximum weight of about 200 grams has been observed to be apt to a full sinter-hardening process and the surface/volume ratio seems to be the critical driving factor. Numerical analysis and experimental tests show that the thermal diffusivity of sintered steels increases as porosity increases.

Keywords: diffusion; hardness; heat treatment; microstructure; powder metallurgy; PM steels; porosity; sinter hardening; thermal diffusivity; metal powders; low-alloy steels; isothermal surfaces; sintered steels; porosity.

DOI: 10.1504/IJMPT.2007.013083

International Journal of Materials and Product Technology, 2007 Vol.28 No.3/4, pp.312 - 337

Available online: 07 Apr 2007 *

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