SANS Investigation of γ´ Precipitate Morphology Evolution in Creep Exposed Single Crystal Ni Base Superalloy

2010 ◽  
Vol 636-637 ◽  
pp. 1475-1482
Author(s):  
Jozef Zrník ◽  
Pavel Strunz ◽  
Maurizio Maldini ◽  
Vadim Davydov

The creep degraded nickel base single crystal superalloy CMSX-4 of two axial orientations [001] and [111] was investigated with aim to assess the structure degradation. Constant load creep tests were conducted in the stress/temperature ranges of 250–780 MPa/750 – 50°C resulting in rupture time variation from 50 to 4000 hours. A combination of scanning electron microscopy (SEM) and non-destructive small-angle neutron scattering method (SANS) was used to investigate the directional coarsening (rafting) of the gamma prime (γ') precipitates in relation to the stress and temperature applied as well as to the initial crystallographic orientation of the specimens. The SANS results are discussed in terms of the correlation with the raft development, the axial orientation of specimen, the creep parameters and the mechanical properties.

2015 ◽  
Vol 750 ◽  
pp. 139-144 ◽  
Author(s):  
De Long Shu ◽  
Su Gui Tian ◽  
Xin Ding ◽  
Jing Wu ◽  
Qiu Yang Li ◽  
...  

By means of heat treatment and creep property measurement, an investigation has made into the creep behaviors of a containing 4.5% Re nickel-base single crystal superalloy at high temperature. Results show that the elements W, Mo and Re are enriched in the dendrite arm regions, the elements Al, Ta, Cr and Co are enriched in the inter-dendrite region, and the segregation extent of the elements may be obviously reduced by means of heat treatment at high temperature. In the temperature ranges of 1070--1100 °C, the 4.5% Re single crystal nickel-based superallloy displays a better creep resistance and longer creep life. The deformation mechanism of the alloy during steady state creep is dislocations slipping in the γ matrix and climbing over the rafted γ′ phase. In the later stage of creep, the deformation mechanism of alloy is dislocations slipping in the γ matrix, and shearing into the rafted γ′ phase, which may promote the initiation and propagation of the micro-cracks at the interfaces of γ/γ′ phases up to the occurrence of creep fracture.


2003 ◽  
Vol 17 (08n09) ◽  
pp. 1608-1614
Author(s):  
Jin Hak Kim ◽  
Tatsuo Tabaru ◽  
Hisatoshi Hirai

Niobium-base in-situ composite Nb-18Si-5Mo-5Hf-2C (in mol%) was prepared and heat-treated at 2070 K for 20 hour. The uni-axile tensile tests at high temperature ranges and the constant load tensile creep tests at 1570 K were performed. The specimen tensile-tested at 1470 K exhibited the excellent UTS of 450 MPa, and the brittle to ductile transition temperature is between 1470 and 1670 K. The specimens creep tested showed good creep strength; the stress exponent is about 5. The tensile fracture surface of the in-situ composite is complex and attributed to cleavage of the Nb 5 Si 3, Nb ss / Nb 5 Si 3 interface separation, ductile rupture of the Nb ss and correlations of these. On the otherhand, the fracture surface of creep tested consists of intergranular above 150 MPa and transgranular below 120 MPa with severely deformed Nb ss .


2014 ◽  
Vol 128 ◽  
pp. 388-391 ◽  
Author(s):  
S. Tang ◽  
Z. Zheng ◽  
L.K. Ning

2004 ◽  
Vol 449-452 ◽  
pp. 545-548
Author(s):  
Tao Jin ◽  
L.R. Liu ◽  
Na Ru Zhao ◽  
Zhi Wang ◽  
Xiao Feng Sun ◽  
...  

Investigation of γ -channel widening behavior in a nickel-base single crystal superalloy during uniaxial tensile creep tests was carried out. Scanning electron microscopy (SEM) was adopted to reveal the microstructural evolution of γ -channel and the dimension of γ -channel. It was found that different tests condition such as temperature, time and stress in tensile creep tests all influenced the γ -channel widening behavior, and a parabolic rate law governs the mean increase value of γ -channel width. The stress and temperature enhanced the γ -channel widening. The γ -channel widening was the result of directionally diffusion of multiatom.


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