he automotive industry employs a considerable amount of sintered parts, mainly as transmission and engine components. Gears are the parts that mostly benefit, in terms of cost saving, from the near net shape P/M technology. However, the porosity along with the heterogeneous microstructure can detrimentally affect the mechanical behaviour, especially the fatigue strength. The possibility of increasing sintered density up to 90% and more, the use of high strength alloys, as well as post sintering treatments have been extensively investigated obtaining consistent increases in the fatigue strength. The present study focuses on the effects of porosity and microstructure on tooth root bending fatigue of small module spur gears. The aim is to investigate the synergistic contribution of pore morphology and microstructure heterogeneity to the initiation of fatigue cracks and to the following crack paths. High density parts produced by high strength pre-alloyed powders were studied. Part of the specimens was case-hardened to obtain a martensitic/bainitic microstructure in the surface layer. Bending fatigue tests up to a fatigue endurance of three million cycles were performed. A careful fractographic analysis was conducted. The obtained results were discussed using the fracture mechanics approach of Murakami, considering the pores as pre-existing defects, whose propagation strongly depends on the microstructural heterogeneity.

The role of pores and microstructural heterogeneity on the tooth root fatigue strength of sintered spur gears / Benedetti, Matteo; Fontanari, Vigilio; Molinari, Alberto; Valcozzena, Pietro; Pahl, Wolfgang. - In: MATEC WEB OF CONFERENCES. - ISSN 2261-236X. - ELETTRONICO. - 165:(2018), p. 02011. (Intervento presentato al convegno 12th International Fatigue Congress, FATIGUE 2018 tenutosi a fra nel 2018) [10.1051/matecconf/201816502011].

The role of pores and microstructural heterogeneity on the tooth root fatigue strength of sintered spur gears

Benedetti, Matteo;Fontanari, Vigilio;Molinari, Alberto;
2018-01-01

Abstract

he automotive industry employs a considerable amount of sintered parts, mainly as transmission and engine components. Gears are the parts that mostly benefit, in terms of cost saving, from the near net shape P/M technology. However, the porosity along with the heterogeneous microstructure can detrimentally affect the mechanical behaviour, especially the fatigue strength. The possibility of increasing sintered density up to 90% and more, the use of high strength alloys, as well as post sintering treatments have been extensively investigated obtaining consistent increases in the fatigue strength. The present study focuses on the effects of porosity and microstructure on tooth root bending fatigue of small module spur gears. The aim is to investigate the synergistic contribution of pore morphology and microstructure heterogeneity to the initiation of fatigue cracks and to the following crack paths. High density parts produced by high strength pre-alloyed powders were studied. Part of the specimens was case-hardened to obtain a martensitic/bainitic microstructure in the surface layer. Bending fatigue tests up to a fatigue endurance of three million cycles were performed. A careful fractographic analysis was conducted. The obtained results were discussed using the fracture mechanics approach of Murakami, considering the pores as pre-existing defects, whose propagation strongly depends on the microstructural heterogeneity.
2018
MATEC Web of Conferences
Les Ulis (France)
EDP Sciences
Benedetti, Matteo; Fontanari, Vigilio; Molinari, Alberto; Valcozzena, Pietro; Pahl, Wolfgang
The role of pores and microstructural heterogeneity on the tooth root fatigue strength of sintered spur gears / Benedetti, Matteo; Fontanari, Vigilio; Molinari, Alberto; Valcozzena, Pietro; Pahl, Wolfgang. - In: MATEC WEB OF CONFERENCES. - ISSN 2261-236X. - ELETTRONICO. - 165:(2018), p. 02011. (Intervento presentato al convegno 12th International Fatigue Congress, FATIGUE 2018 tenutosi a fra nel 2018) [10.1051/matecconf/201816502011].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11572/230634
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