Damage evolution in sinter-hardening powder-metallurgy steels during tensile and fatigue loading

Straffelini, Giovanni; Benedetti, M.; Fontanari, V.

doi:10.1016/j.matdes.2014.04.027

Cited by 28 publications

(25 citation statements)

References 24 publications

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“…In general, a progression with increasing sintering temperature from irregular, interconnected pores to spherical pores within the grains or located at the grain boundaries was observed ( Figure 5). This is a desirable change since spherical pores reduce stress concentrations thereby improving fatigue life and UTS [20][21][22].…”

Section: Porosity Microstructure Observations and Elemental Analysesmentioning

confidence: 99%

Powder bed binder jet printed alloy 625: Densification, microstructure and mechanical properties

et al. 2016

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Powder bed binder jet printing is an additive manufacturing method in which powder is deposited layer-by-layer and selectively joined in each layer with binder. Since the powder does not melt during printing, the density after printing is about 50%, and sintering is needed to densify as-printed parts. In this study, we investigate the effect of sintering temperature on density, microstructure, phase formation and mechanical properties of power bed binder jet printed alloy 625 parts. To determine the sintering temperatures, the as-received powder was subjected to differential scanning calorimetry analysis, and printed samples were cured and sintered at various temperatures under high vacuum. Density measurements, elemental analysis, phase formation and microstructure of as-printed, cured and sintered samples were investigated compared with mechanical properties. Results indicate that a fully densified parts with densities of up to 99.6%, as well as favorable mechanical properties (hardness of up to 238 HV 0.1 and UTS of up to 612 MPa) may be obtained for the sample sintered at 1280 °C. It is concluded that alloy 625 produced by powder bed binder jet printing can achieve similar density and mechanical properties as cast alloy 625.

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Section: Porosity Microstructure Observations and Elemental Analysesmentioning

confidence: 99%

Powder bed binder jet printed alloy 625: Densification, microstructure and mechanical properties

et al. 2016

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“…It can be observed that, for relatively low sintered density, the damage usually occurs very early, located at the necks between powder particles, which are the weakest point of the microstructure. A widespread damage occurs and the final failure is often caused by the coalescence of numerous defects previously initiated [11]. By increasing the sintered density to high values, even up to near-full density, the triggering of the damage is delayed and the pores can be regarded as local defects of different criticality, able to concentrate the stresses and to act as internal notches or, in certain situations, even as cracks [5, 12 to 15].…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2018

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Abstract. The 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.

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“…A great amount of studies have been focused on PM processing of steels. The influence of porosity on the fracture behavior was studied in depth [1] and the role of material density on the fatigue behavior was underlined [2]. Due to porosity of PM materials, the procedure for characterization of their microstructure was reviewed [3].…”

Section: Introduction and Backround Informationmentioning

confidence: 99%

Failure analysis of an EDM machined mold-printing die used for the production of truck spare parts

Leptidis

Medrea

Chicinaş

2016

Engineering Failure Analysis

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Damage evolution in sinter-hardening powder-metallurgy steels during tensile and fatigue loading

Cited by 28 publications

References 24 publications

Powder bed binder jet printed alloy 625: Densification, microstructure and mechanical properties

Powder bed binder jet printed alloy 625: Densification, microstructure and mechanical properties

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

Failure analysis of an EDM machined mold-printing die used for the production of truck spare parts

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