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Rolling contact fatigue behaviour of sintered steels. Endurable Hertzian pressures and damage mechanisms

: Lipp, K.; Sonsino, C.M.; Pohl, D.; Hock, S.

European Powder Metallurgy Association -EPMA-:
Powder Metallurgy World Congress & Exhibition 1998. Proceedings. Vol. 3: Powder injection moulding, pm steels, applications, joining, high alloy steels, electrical materials
Shrewsbury: EPMA, 1998
ISBN: 1-89907-209-8
S.143-148 : Ill., Lit.
Powder Metallurgy World Congress & Exhibition (PM) <1998, Granada>
Fraunhofer LBF ()
contact friction; Ermüdungsschaden; Fahrzeugbau; fatigue damage; fatigue strength; fatigue strength test; forging part; Haftreibung; heat treatment; Hertzian contact; Hertz'sche Pressung; Last; load; material characteristic; material property; metal; Metall; Porosität; porosity; Probestab; rolling friction; rolling stress; Rollreibung; Schmiedestück; Schwingfestigkeit; Schwingfestigkeitsversuch; sintered steel; Sinterstahl; Spannung; specimen; stress; test; tribologic stress; tribologische Beanspruchung; vehicle construction; Versuch; Wälzbeanspruchung; Wärmebehandlung; Werkstoffeigenschaft; Werkstoffkennwert

The knowledge about the behaviour of sintered steels under Hertzian pressure is important for the selection of the appropriate material composition and densification technology. While the rolling contact fatigue properties of sintered steels are determinated without superposition of sliding in most investigations, the realistic and most severe condition on flanks of gears during operation is the presence of sliding (relative velocity between sliding surfaces). The rolling contact fatigue tests with a sliding of -24 per cent were performed with the mixed alloys Fe+1.5 per cent Cu, carbonitrided, Fe+1.5 per cent Cu + 0.5 per cent C, as-sintered as well as quenched and tempered, diffusion alloyed powder Fe-4.0 per cent Ni-1.5 per cent Cu-0.5 per cent Mo, as-sintered, plasmanitrided, carbonitrided, case hardened and additionally mixed with 0.5 per cent C and prealloyed powders Fe-4.0 per cent Ni-0.5 per cent Mo and Fe-1-5 per cent Mo with addition of Cu and C in different heat treatments. The densities investigated were 6.8, 7.1, 7.4 and 7.8 g/cm 3. The tribological environment was the gear-box oil SAE 80 at 800 deg C. With superposition of sliding the highest rolling contact fatigue strength was achieved with powder forged specimens (density of 7.8 g/cm 3 ). An optimum for the sintered specimens in the range of 6.8 to 7.4 g/cm 3 was found at about 7.1 g/cm 3 for the most sintered steels independent of the heat treatment. This is due to effects based on open and closed porosity in interaction with the tribological environment.