Volume 12 - Fractography Part 11 ppsx

[...]... are of the lateral (tension or screw-head-side) surface of plate subjected to fatigue loading Fig 664: Lateral surface of plate Note slip-band activity and intrusions formed by slip bands SEM, 187× Fig 665: Higher-magnification view of area on lateral surface of plate Note microcracking at slip bands and the crack being formed at a grain-boundary triple point SEM, 116 0× Fig 666: Fatigue crack formed... inclusions on FCP in ASTM A533B The conventionally melted electric furnace steel was water quenched from 900 °C (1650 °F), tempered at 670 °C (124 0 °F), air cooled, stress relieved at 595 °C (110 0 °F), and then furnace cooled FCP specimen tested in the through-thickness (S-T, S-L) orientations Direction of fatigue crack propagation is toward the top Fig 588: Fracture surface of SL oriented FCP test specimen... rounded-type cavities (Fig 691) Fig 688: Wedge-type cavities in an AISI type 316 sample that failed by creep These cavities are usually associated with cracking at grain-boundary triple points 100× Fig 689: Wedge-type cavities (wedge cracks) form at triple points due to grain-boundary sliding and may be promoted by decohesion at interfaces between grain- boundary precipitates and the matrix, as shown... thickness has partially transformed, particularly in the vicinity of pores Carbon content of the bulk material was 0.22 wt%, compared with the 0.03 wt% max specified for type 316L Carbon content at the outside diameter was 1.40 wt% 35× Fig 656: Structure near through-wall crack at outside diameter of failed filter tube Mixed carbides (gray phases) dominate Only a very few small, light-colored islands... Marshall Space Flight Center) μ In-service failure of a paper machine suction couch roll due to intergranular stress-corrosion cracking (SCC) The centrifugally cast roll was made of ACI CF-8M (~AISI type 316) and measured 8.8 m (29 ft) long and 1.2 m (49 in.) in diameter with a 65-mm (2.5-in.) wall thickness Cracking initiated near the outside diameter of the roll, 2.7 m (9 ft) from the driven end, and... intergranular cracking along sensitized, near-equiaxed grain boundaries Ferric chloride etch, 20× (F.W Tatar, Factory Mutual Research Corporation) Brittle fracture due to severe carburization of a porous metal filter tube The P/M type 316L tube (5μm nominal filter grade) was used in a coal-gasification pilot plant to remove entrained ash and char particles from the raw-product gas stream Failure occurred after... 690: Creep failure due to wedge cracking at triple points produces a rough fracture surface with identifiable grain-boundary precipitates For example, carbides and σ-phase particles are found on the fracture surface of this type 316 stainless steel TEM replica, 10,000× Fig 691: Rounded-type voids in type 316L weld metal Sample failed in creep at high temperature 100× (I Le May, Metallurgical Consulting... deformation SEM, 86× Fig 669: Higher-magnification view of representative area in Fig 668 Note slip-band activity and intersecting slip bands See also Fig 664, 665, 666, and 667 SEM, 859× (H.R Shetty, Zimmer Inc.) Failure of AISI type 316L Jewett nail (hip implant) due to improper installation Fig 680: Fractured implant after removal from body The threaded tip of an impactor-extractor tool is inserted by... located where the side plate (left) meets the tri-finned nail (right) During installation, the threaded tip of the tool broke off The jagged edge of the broken tool then gouged the rim of the chamfer Even so, the operation was judged a qualified success The implant failed 4 weeks after installation Fig 681: Close-up of fractured Jewett nail Broken tip of impactor-extractor is in nail portion of implant at... 682: Plate end of fractured impact Fracture originates on ridge (R) of chamfer The chamfer-fracture surface interface is indicated by I (see Fig 684, 685, 686, and 687) Fig 683: Close-up of area near fracture origin R in Fig 682 Tensile stress was concentrated at groove G1, created by fractured edge of impactor-extractor tool Fracture propagated along this groove Also note second and third grooves (G2 . outside diameter with a 150-mm (6-in.) thick wall and was designed for 67-MPa (9.7-ksi) internal pressurization. The preflawed vessel contained a semielliptical fatigue-cracked defect measuring. (1650 °F), tempered at 670 °C (124 0 °F), air cooled, stress relieved at 595 °C (110 0 °F), and then furnace cooled. FCP specimen tested in the through-thickness (S-T, S-L) orientations. Direction. At the low 22-MPa m (20-ksi in ) level (Fig. 582), fatigue damage is by striation formation in the interinclusion material of an inclusion formation. At the high 55-MPa m (50-ksi in ) level