Creep strength evaluation of 9Cr steel MAG welding joint.

2016 ◽  
Vol 2016 (0) ◽  
pp. J0310202
Author(s):  
Keisuke CHIWAKI ◽  
Takashi OGATA
Keyword(s):  
Creep Strength ◽  
Mag Welding ◽  
Strength Evaluation ◽  
Welding Joint ◽  
9Cr Steel

Creep Strength of Dissimilar Weld Using High B-9Cr Steel for A-USC Boiler

2013 ◽  
Author(s):  
Masaaki Tabuchi ◽  
Hiromichi Hongo ◽  
Fujio Abe
Keyword(s):  
Creep Strength ◽  
Materials Science ◽  
Ferritic Steels ◽  
Creep Tests ◽  
Fine Grained ◽  
Dissimilar Weld ◽  
9Cr Steel ◽  
Weld Thermal Cycle ◽  
Dissimilar Welds ◽  
Steel Welds

The research project aiming to commercialize 700°C class pulverized coal power system; advanced ultra-super critical (A-USC) pressure power generation has been conducted in Japan from 2008. In A-USC boilers, Ni base or Ni-Fe base alloys are used for high temperature parts at 650–700°C and advanced high Cr ferritic steels are planning to be used at the temperatures lower than 650°C. Because the high B-9Cr steel developed in National Institute for Materials Science (NIMS) has improved creep strength in weldments, it is one of the candidate materials for A-USC boilers. In the present paper, the creep tests of the dissimilar welds between high B-9Cr steels and Ni base alloys were conducted. In the heat affected zone (HAZ) of the high B-9Cr steels, fine-grained microstructures were not formed and grain size of the base metal was retained. Free boron on the grain boundaries is considered to affect the mechanisms of the α-γ transformation during weld thermal cycle. Consequently, the creep rupture lives of the dissimilar welds between high B-9Cr steels and Ni base alloys were 5–10 times longer than those of the conventional 9Cr steel welds at 650°C.

scholarly journals Stress Relaxation Testing of Service Exposed IN738 for Creep Strength Evaluation

1999 ◽  
Author(s):  
David A. Woodford
Keyword(s):  
Stress Relaxation ◽  
Creep Strength ◽  
Standard Size ◽  
Strength Evaluation ◽  
Management Procedure ◽  
Section Size ◽  
Long Time ◽  
Evaluation Measurement ◽  
Miniature Specimens ◽  
Base Data

Standard size and miniature specimens of IN738 were taken from a service exposed turbine blade and vane for comparative stress relaxation testing at 800C, 850C and 900C. Base data taken from root section material were used to construct stress vs. creep rate parametric curves which could be used directly in design. Up to five decades in creep rates were obtained at each temperature from tests lasting less than one day. The data were also presented in the form of stress vs. predicted times to 0.5% creep which compared well with available long time creep data. Differences were noted in specimens taken from different locations in the airfoil regions which probably resulted from differences in grain size or orientation. Based on these measurements it was concluded that there was no significant effect of section size on creep strength as defined by this test, and that the alloy was quite insensitive to prior deformation and thermal exposures. A life management procedure, using a combination or creep strength evaluation based on the stress relaxation test and a separate fracture evaluation measurement, is outlined in which end of useful life is defined in terms of minimum acceptable performance levels.

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