Influence of MnS on Fatigue Fracture Surface Morphology of Nickel Alloyed PM Steel

Drar, H.; Bergmark, Åke

doi:10.1179/pom.1995.38.4.299

Cited by 8 publications

(9 citation statements)

References 6 publications

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“…Thus, depending on the material studied, some have shown that the presence of MnS can be detrimental to mechanical properties, [9][10][11] while others have reported no effect. [1,2,12] In general, the influence of MnS particles will depend greatly on the amount of MnS and on the density of the parts.…”

Section: Introductionmentioning

confidence: 99%

“…[13] There is quite a consensus on the effect of MnS additions on static mechanical properties (yield strength (YS) and ultimate tensile strength (UTS)), because adding up to 0.5 wt pct MnS will have little effect on the mechanical properties for materials at density less than 7.2 g/cm 3 . [1,2,12,14] Little effect on mechanical properties is seen at very high density powder forged materials for contents up to 0.3 wt pct MnS. [15] Sanderow et al have studied the effect of admixing up to 0.8 wt pct MnS on the mechanical properties of P/M steels at different densities.…”

Section: Introductionmentioning

confidence: 99%

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Microstructural Characterization and Mechanical Properties of Free-Machining Sintered Steel Parts Containing up to 1 Wt Pct MnS

Bernier

Baïlon

L’Éspérance

2009

Metall Mater Trans A

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The effect of prealloying MnS up to 1.0 wt pct on the microstructural features of nonmetallic inclusions and their impacts on tensile and fatigue properties of 7.0 g/cm 3 powder metal (P/M) steel (Fe-2.0Cu-0.7C) have been investigated. As the MnS content increases, larger, more irregular, and more closely spaced inclusions are obtained. While no significant impact on both static and dynamic properties was observed when prealloying up to 0.65 wt pct MnS, a decrease of more than 15 pct of the ultimate tensile strength and of the endurance limit was found when the MnS content reached 1.0 wt pct. The decrease in the ultimate tensile stress is attributed to a lower ductility of the sinternecks, as void initiation and void growth were promoted at lower stress levels by larger inclusions. The larger size of the MnS particles and the lower mean free path between nonmetallic inclusions also favor the initiation of microcracks and their coalescence into cracks, reaching fatigue fracture earlier.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Microstructural Characterization and Mechanical Properties of Free-Machining Sintered Steel Parts Containing up to 1 Wt Pct MnS

Bernier

Baïlon

L’Éspérance

2009

Metall Mater Trans A

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“…Detailed fatigue propagation of surface cracks in relation to the pores has been studied by Danninger 4 and Polasik 5 . Drar 6 examined the influence of MnS on fatigue crack propagation.…”

Section: Introductionmentioning

confidence: 99%

Fatigue crack path in Cu–Ni–Mo alloyed PM steel

Bergmark

Alzati

2004

Fatigue Fract Eng Mat Struct

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A B S T R A C T A detailed qualitative fatigue crack path study is made on Ni-Cu alloyed powder metallurgy (PM) steel with Mo prealloyed base powder. The microstructure is characterized by upper bainitic cores of the base powder particles surrounded by a Cu-rich martensite with islands of Ni-rich austenite. Earlier observations have shown that the visible surface cracks do not pass through the Ni-rich areas. The aim of the present study is to find the crack path in relation to the Cu-rich martensite and the Ni-rich austenite also below the surface. Successive grinding in steps of about 20 µm is made, and the surface crack in each level is recorded by light optical microscope (LOM). The main part of the crack path is found through high temperature bainite or along the interface between martensite and high temperature bainite. Ni-rich austenite is surrounded by martensite that hinders the crack from entering into austenite. The result indicates that austenite as such is not a strong crack stopper.

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“…This is not the case for PM materials. Generally the fatigue crack propagation mechanism which is described in PM literature is that through the necks of sintered materials by dimple rupture from microvoid coalescence [3-81. In a recent work [9,10], the attention was drawn to the zone of the initial fatigue crack growth. This zone which contained the main fatigue crack origin is not fully explored in PM literature.…”

Section: Introductionmentioning

confidence: 99%

“…In our earlier work [9,10], the fatigue fracture morphology of two Ni-sintered steels with different contents of pores and MnS was examined. Fractography on those specimens which failed after extensive cyclic loading invariably revealed that fatigue cracks initiated at pores located at or near the specimen surface.…”

Section: Introductionmentioning

confidence: 99%

Initial Fracture Mechanisms in Nickel Alloyed Pm Steel

Drar

Bergmark

1997

Fatigue Fract Eng Mat Struct

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Initial fatigue crack propagation mechanisms at near threshold conditions were studied for four nickel-alloyed, powder-metallurgy (PM) steels. Fatigue fracture surfaces were obtained by testing smooth rectangular specimens at 30 Hz and under constant amplitude and zero mean stress conditions. Materials based on Distaloy AE were used in two densities, namely 7.15 and 7.45 g/cm3.All the fracture surfaces were composed of three morphological regions (1) a macrocrack initiation region R1 where cracks propagated preferentially through particles (ii) a macrocrack growth region R2 and (iii) an unstable crack growth region R3 where cracks propagated preferentially between particles. Initial fatigue crack growth, in region R1, was controlled by the propagation of short cracks whose dimensions were comparable to the material microstructure. The subsequent fatigue crack growth in regions R2 and R3 was controlled by ductile rupture between microvoids. Transparticle fracture in region R1 was independent of pore distribution, while interparticle fracture in regions R2 and R3 was dependent on pore distribution.

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Influence of MnS on Fatigue Fracture Surface Morphology of Nickel Alloyed PM Steel

Cited by 8 publications

References 6 publications

Microstructural Characterization and Mechanical Properties of Free-Machining Sintered Steel Parts Containing up to 1 Wt Pct MnS

Microstructural Characterization and Mechanical Properties of Free-Machining Sintered Steel Parts Containing up to 1 Wt Pct MnS

Fatigue crack path in Cu–Ni–Mo alloyed PM steel

Initial Fracture Mechanisms in Nickel Alloyed Pm Steel

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