scholarly journals Creep Degradation Mechanism and Creep Damage Assessment Based on Hardness Method of Precipitation Strengthened Wrought Ni-Based Superalloy

2019 ◽  
Vol 68 (9) ◽  
pp. 673-679
Author(s):  
Shun OINUMA ◽  
Reki TAKAKU ◽  
Yujiro NAKATANI ◽  
Masao TAKEYAMA
Keyword(s):  
Damage Assessment ◽  
Degradation Mechanism ◽  
Creep Damage ◽  
Creep Degradation

scholarly journals Creep Damage Assessment of High Chromium Steel Forging through EBSD Method and Hardness Measurement

2008 ◽  
Vol 74 (739) ◽  
pp. 323-328 ◽  
Author(s):  
Kazunari FUJIYAMA ◽  
Keita MORI ◽  
Daisuke KANEKO ◽  
Takahide MATSUNAGA ◽  
Hirohisa KIMACHI
Keyword(s):  
Damage Assessment ◽  
Creep Damage ◽  
Hardness Measurement ◽  
Chromium Steel ◽  
High Chromium ◽  
Steel Forging ◽  
Ebsd Method

A Metallographic Technique for High Temperature Creep Damage Assessment in Single Crystal Alloys

1998 ◽  
Author(s):  
Pamela Henderson ◽  
Jacek Komenda
Keyword(s):  
High Temperature ◽  
Single Crystal ◽  
Creep Strain ◽  
Creep Deformation ◽  
Damage Assessment ◽  
Creep Damage ◽  
High Temperature Creep ◽  
Gamma Prime ◽  
Aspect Ratios ◽  
Metallographic Technique

The use of single crystal (SX) nickel-base superalloys will increase in the future with the introduction of SX blades into large gas turbines for base-load electricity production. Prolonged periods of use at high temperatures may cause creep deformation and the assessment of damage can give large financial savings. A number of techniques can be applied for life assessment, e.g. calculations based on operational data, non-destructive testing or material interrogation, but because of the uncertainties involved the techniques are often used in combination. This paper describes a material interrogation (metallographic) technique for creep strain assessment in SX alloys. Creep tests have been performed at 950°C on the SX alloy CMSX-4 and quantitative microstructural studies performed on specimens interrupted at various levels of strain. It was found that the strengthening γ′-particles, initially cuboidal in shape, coalesced to form large plates or rafts normal to the applied stress. The γ-matrix phase also formed plates. CMSX-4 contains ∼ 70 vol % γ′-particles and after creep deformation the microstructure turned itself inside out, i.e. the gamma “matrix” became the isolated phase surrounded by the γ′-“particles”. This can cause problems for computerised image analysis, which in this case, were overcome with the choice of a suitable measurement parameter. The rafts reached their maximum length before 2% strain, but continued to thicken with increasing strain. Although of different dimensions, the aspect ratios (length/thickness ratio) of the gamma-prime rafts and the gamma plates were similar at similar levels of strain, increasing from ∼1 at zero strain to a maximum of ∼3 at about 1–2 % strain. Analysis of microstructural measurements from rafting studies on SX alloys presented in the literature showed that the aspect ratios of the γ- and γ′-phases were similar and that at a temperature of 950–1000°C a maximum length/thickness ratio of about 2.5–3.5 is reached at 1 to 2% creep strain. Measurement of gamma-prime raft or (or gamma plate) dimensions on longitudinal sections of blades is thus a suitable method for high temperature creep damage assessment of SX alloys. This gives a considerable advantage over conventional Ni-base superalloys whose microstructures are usually very stable with respect to increasing creep strain.

Creep Damage Assessment Through EBSD Method and Hardness Measurement for a High Chromium Turbine Rotor Steel Forging

2007 ◽  
Author(s):  
Kazunari Fujiyama ◽  
Takashi Saito ◽  
Keita Mori ◽  
Takahisa Hino ◽  
Ryuichi Ishii
Keyword(s):  
Electron Microscope ◽  
Dislocation Density ◽  
Damage Assessment ◽  
Creep Damage ◽  
Life Assessment ◽  
Rotor Steel ◽  
Creep Tests ◽  
Nano Indentation ◽  
Steel Forging ◽  
The Relationship

10Cr-1Mo-1W-VNbN steel forging for steam turbine rotors was investigated using TEM (Transmission Electron Microscope), SEM (Scanning Electron Microscope) with EBSD (Electron BackScattering Diffraction pattern) method and nano-indentation tester for the assessment of microstructural change during creep damage process. Long term creep rupture tests and interrupted creep tests were conducted for the subject material and then effective damage parameters were assessed and compared with each other. Dislocation substructure which was observed through TEM thin foil method showed increasing lath/block width according to creep damage accumulation and the same feature was observed through EBSD IPF mapping more clearly and easily. EBSD KAM mapping was also conducted and averaged KAM was shown as an effective index for measuring dislocation microstructural changes during creep. Nano-indentation tests were conducted at the same position of EBSD measurement, which revealed that there was a good correlation between hardness value and the square root of averaged KAM. The differential equation of dislocation density with creep time was arranged to estimate the relationship between averaged KAM and time through the relationship between hardness and dislocation density. The creep damage estimation curves were obtained successfully by the equation expressed with stress and temperature term. The dislocation density based creep damage assessment curves could be effective for creep life assessment of high temperature components.

scholarly journals Study on Creep Damage Assessment Method for Mod. 9Cr-1Mo Steel by Sampling Creep Testing with Thin Plate Specimen

2019 ◽  
Vol 68 (5) ◽  
pp. 421-428 ◽  
Author(s):  
Hideyuki KANAYAMA ◽  
Noritake HIYOSHI ◽  
Fumio OGAWA ◽  
Mie KAWABATA ◽  
Takamoto ITOH ◽  
...  
Keyword(s):  
Thin Plate ◽  
Damage Assessment ◽  
Creep Damage ◽  
Assessment Method ◽  
Creep Testing ◽  
Plate Specimen
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