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Sigl L.S.,Sinterstahl GmbH | Delarbre P.,Sinterstahl GmbH
Fenmo Yejin Jishu/Powder Metallurgy Technology | Year: 2013

Experimental access to the in-situ strength properties of components is difficult, which explains why such data are not generally available. The present paper reproduces a methodology which was recently introduced to directly access the strength properties of components. Such information is retrieved from small rectangular bars (size ≈ 40 mm×5 mm×5 mm) which are prepared from a component by water-jet cutting and subsequent grinding. Using a synchronizer-hub as a typical P/M component, the tensile strength, the impact resistance and the transverse rupture strength in 3-point bending were evaluated from these bars for a high-alloyed Fe(Cr, Mo) P/M steel, and compared to the strength and impact properties of conventional tensile specimens (DIN EN ISO 2740). Within the limits of experimental error, the data sets obtained from components and specimens are fully consistent. To confirm the validity of the comparison, the similarity of both specimen types is verified by a comprehensive chemical and microstructural characterization. Finally, a correlation between the transverse rupture strength and the tensile strength of the small tensile specimens is established. Source


Sigl L.S.,Sinterstahl GmbH | Delarbre P.,Sinterstahl GmbH
Fenmo Yejin Jishu/Powder Metallurgy Technology | Year: 2013

A number of (Cr, Mo)-alloyed PM-steels was prepared from commercial powder (3wt.% Cr, 0.5wt.% Mo) and sintered to various oxygen levels. The microstructure and the fractographic appearance of these materials were analyzed. Oxygen being generally precipitated as particulate Cr2O3 was found to be concentrated in planes along former particle boundaries. This spatial configuration controls the nucleation and spacing of micro-voids during plastic deformation of sintering necks and significantly reduces ductility and fatigue resistance upon increasing oxygen content. Finally it is shown that (Cr, Mo)-PM-steels combining both high strength and good ductility can be obtained by high temperature sintering which reduces the oxygen content of such materials below 0.05wt.%. Source


Sigl L.S.,Sinterstahl GmbH | Rau G.,Sinterstahl GmbH | Krehl M.,Sinterstahl GmbH
Fenmo Yejin Jishu/Powder Metallurgy Technology | Year: 2012

A helical PM gear for a passenger car gear box was manufactured by pressing, sintering and selective surface densification by transverse rolling. The evolution of the gear properties in terms of microstructure, gear geometry, surface roughness and DIN-quality is monitored at each step of the processing sequence. The geometry of the PM gear is compared to a conventional wrought steel gear (DIN-quality 7) being currently used in the gear box. It is shown that PM gears can be manufactured well within the DIN quality 8 tolerance fields. Furthermore it is demonstrated that alignment and profile errors is reduced in the sequence of processing. While wrought gears have less alignment and profile errors, PM gears are superior in terms of run-out and pitch errors as well as surface roughness. Source

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