Handbook Fractography (1998) WW Part 12 pot

[...]... did not crack The well-protected superalloy failed via multiple internal cracking originating at microporosity (arrow) SEM, 12. 5× Fig 858: High-magnification view of micropore at arrow in Fig 857 SEM, 280× Fig 859: Fracture surface of coated sample cycled between 650 and 1050 °C (120 0 and 1920 °F) in a thermomechanical fatigue test The NiCoCrAlY coating was placed in tension during the low-temperature... 0.005% C, remainder Ni Heat-treated notched samples were stress relieved and then tensile tested in either helium (control samples) or hydrogen at 35 MPa (5 ksi) and room temperature Cross-head speed, 2 .12 μ/s; notched strength ratio H2/He, 0.14 Fig 828: Fracture surface of control sample tested in helium 4.6× Fig 829: Higher-magnification view of fracture surface in Fig 828 Note ductile failure mode... Space Flight Center) Fatigue and creep fractures of case and hot isostatically pressed IN-738 tested in a salt environment (40% MgSO4, 59% Na2SO4, 1% NaCl) at 705 °C (1300 °F) Samples heat treated 2 h at 1120 °C (2050 °F), air cool; 14 h at 845 °C (1550 °F), air cool Fig 832: Fatigue fracture surface Test conditions: 483 MPa (70 ksi) ± 207 MPa (30 ksi); 102,000 cycles at failure Fractograph shows region... specimen broke after 49 h of testing Figure 844 is a TEM p-c replica of an area at the arrow in Fig 843, showing some evidence of intergranular separation and some facets of what appear to be cleaved particles (as at A) of intermetallic compounds Figure 845 is a TEM p-c replica of another area at the arrow in Fig 843, showing evidence of glide-plane decohesion (at A's) as well as smooth areas of stretching... applied stress) SEM, 50× (J.K Tien, T.E Howson, and J.E Stulga, Columbia University) Fatigue fracture of Nimonic 115 at room temperature and 845 °C (1550 °F) Thermal treatment: solution treat 24 h at 123 0 °C (2250 °F); furnace cool to 1000 °C (1830 °F) to nucleate precipitation; air cool; precipitation age for 96 h at 1000 °C (1830 °F); air cool Test conditions: R = -1, constant strain rate ramps Fig... propagation until overload 5.7× Fig 854: Substructure of sample in Fig 853 consists of dense, homogeneous dislocation tangles Note well-defined slip bands that have sheared γ' precipitates TEM thin foil, 12, 400× Fig 855: Fracture surface of sample tested at 845 °C(1550 °F) Failure due to crack initiation in a stage II mode around most of the circumference 5.8× Fig 856: Substructure of sample in Fig 855... Fig 818: 8× Figures 819 and 820 are TEM views, at different magnifications, taken from one of the highreflectivity areas in Fig 818 The shiny aspect was due to flat platelets resulting from cleavage of particles of unidentified composition Note that in both views there are tear dimples between the reflecting facets Figure 821 reveals that the structure in the low-reflectivity area in this fracture surface... Lewis Research Center) Fatigue fracture of Udimet 720 tested in a salt environment at 705 °C (1300 °F) Sample heat treatment and salt composition same as in Fig 861 Test conditions: 827 MPa ± 69 MPa (120 ksi ± 10 ksi), 5000 cycles to failure Fig 863: Fracture surface shows intergranular origin at grain-boundary triple point (near bottom) with subsequent transgranular propagation Because origin is near . high- reflectivity areas in Fig. 818. The shiny aspect was due to flat platelets resulting from cleavage of particles of unidentified composition. Note that in both views there are tear dimples between the. helium (control samples) or hydrogen at 35 MPa (5 ksi) and room temperature. Cross-head speed, 2 .12 μ/s; notched strength ratio H 2 /He, 0.14. Fig. 828: Fracture surface of control sample tested. environment (40% MgSO 4 , 59% Na 2 SO 4 , 1% NaCl) at 705 °C (1300 °F). Samples heat treated 2 h at 1120 °C (2050 °F), air cool; 14 h at 845 °C (1550 °F), air cool. Fig. 832: Fatigue fracture surface.