Improving the Toughness of 3-1/2NiCrMoV Steam Turbine Disk Forgings

1989 ◽  
Vol 111 (1) ◽  
pp. 61-70 ◽  
Author(s):  
R. L. Bodnar ◽  
K. A. Taylor ◽  
K. S. Albano ◽  
S. A. Heim
Keyword(s):  
Heat Treatment ◽  
Stress Corrosion ◽  
Steam Turbine ◽  
Stress Corrosion Cracking ◽  
Turbine Disk ◽  
Notch Toughness ◽  
Preliminary Heat Treatment ◽  
Final Heat Treatment ◽  
Final Heat ◽  
Turbine Disks

Due to the in-service stress corrosion cracking of some 3-1/2NiCrMoV steam turbine disks, the Charpy V-notch toughness requirements for replacement forgings have dramatically increased in recent years. In response to the new requirements, several avenues for improving the toughness of 3-1/2NiCrMoV steel have been explored and are discussed in this paper. Improvements in forging practice, preliminary heat treatment, final heat treatment and composition are recommended which allow the new requirements to be met.

Prediction of Failures of Low-Pressure Steam Turbine Disks

1997 ◽  
Vol 119 (4) ◽  
pp. 393-400 ◽  
Author(s):  
C. Liu ◽  
D. D. Macdonald
Keyword(s):  
Stress Corrosion ◽  
Steam Turbine ◽  
Stress Corrosion Cracking ◽  
Wilson Line ◽  
Corrosion Damage ◽  
Low Pressure ◽  
Corrosion Cracking ◽  
Localized Corrosion ◽  
Pressure Steam ◽  
Turbine Disks

Localized corrosion phenomena, including pitting corrosion, stress corrosion cracking, and corrosion fatigue, are the principal causes of corrosion-induced damage in electric power-generating facilities and typically result in more than 50 percent of the unscheduled outages. In this paper, we describe a deterministic method for predicting localized corrosion damage in low-pressure steam turbine disks downstream of the Wilson line, where a condensed, thin electrolyte layer exists on the steel disk surfaces. Our calculations show that the initiation and propagation of stress corrosion cracking (SCC) is not very sensitive to the oxygen content of the steam, but is sensitive to the conductivity of the condensed liquid layer and the stresses (residual and operational) that the disk experiences in service.

scholarly journals Stress Corrosion Cracking of Additively Manufactured Alloy 625

Materials ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6115
Author(s):  
Marina Cabrini ◽  
Sergio Lorenzi ◽  
Cristian Testa ◽  
Francesco Carugo ◽  
Tommaso Pastore ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Hydrogen Embrittlement ◽  
Strain Rate ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
High Strain ◽  
Corrosion Cracking ◽  
Slow Strain Rate ◽  
Laser Source ◽  
Alloy 625

Laser bed powder fusion (LPBF) is an additive manufacturing technology for the fabrication of semi-finished components directly from computer-aided design modelling, through melting and consolidation, layer upon layer, of a metallic powder, with a laser source. This manufacturing technique is particularly indicated for poor machinable alloys, such as Alloy 625. However, the unique microstructure generated could modify the resistance of the alloy to environment assisted cracking. The aim of this work was to analyze the stress corrosion cracking (SCC) and hydrogen embrittlement resistance behavior of Alloy 625 obtained by LPBF, both in as-built condition and after a standard heat treatment (grade 1). U-bend testing performed in boiling magnesium chloride at 155 and 170 °C confirmed the immunity of the alloy to SCC. However, slow strain rate tests in simulated ocean water on cathodically polarized specimens highlighted the possibility of the occurrence of hydrogen embrittlement in a specific range of strain rate and cathodic polarization. The very fine grain size and dislocation density of the thermally untreated specimens appeared to increase the hydrogen diffusion and embrittlement effect on pre-charged specimens that were deformed at the high strain rate. Conversely, heat treatment appeared to mitigate hydrogen embrittlement at high strain rates, however at the slow strain rate all the specimens showed a similar behavior.

Effects of Cold Working and Heat Treatment on Caustic Stress Corrosion Cracking of Alloy 800M

2005 ◽  
Vol 297-300 ◽  
pp. 993-998 ◽  
Author(s):  
Chun Bo Huang ◽  
Guang Fu Li ◽  
Zhan Peng Lu ◽  
Jian Min Zeng ◽  
Wu Yang
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Cold Working ◽  
Corrosion Cracking ◽  
Caustic Solution ◽  
Surface Films ◽  
Microstructure Examination ◽  
Increasing Temperature

The effects of cold working and heat treatment on caustic stress corrosion cracking (SCC) of mill annealed (MA) alloy 800M in boiling solution of 50%NaOH+0.3%SiO2+0.3%Na2S2O3 were investigated by means of microstructure examination, tensile test, X-ray stress analysis, SCC testing of C-rings, Auger electron spectroscopy (AES), scanning electron microscopy (SEM) and metallography. The microstructure of alloy 800M under tested conditions was austenite. With a train of 25% by cold working, the grains of alloy 800M became longer, yield strength (YS) and ultimate tensile strength (UTS) increased, elongation (δ ) decreased, residual stress and the susceptibility to SCC increased. With increasing temperature of heat treatment of alloy 800M with cold working, the grains became bigger , residual stress, YS and UTS decreased and δ increased, the susceptibility to SCC of alloy 800M decreased. In boiling caustic solution, SCC cracks on the surfaces of C-ring specimens polarized potentiostatically at –20mV/SCE initiated from pitting and propagated along grain boundaries. AES analysis indicated that the surface films on MA alloy 800M were enriched in nickel and depleted in iron and chromium.

Dense and smooth epitaxial BaTiO3 thin films by the dipping-pyrolysis process

1999 ◽  
Vol 14 (2) ◽  
pp. 592-596 ◽  
Author(s):  
S. Kim ◽  
T. Fujimoto ◽  
T. Manabe ◽  
I. Yamaguchi ◽  
T. Kumagai ◽  
...  
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Heat Treatment ◽  
Oxygen Partial Pressure ◽  
Smooth Surface ◽  
Precursor Solution ◽  
Final Heat Treatment ◽  
Pyrolysis Process ◽  
Low Oxygen ◽  
Final Heat

Dense and smooth BaTiO3 thin films were prepared on SrTiO3 (100) substrates by the dipping-pyrolysis process using a mixed precursor solution of barium and titanium naphthenates. Combination effects of prefiring [at 150–450 °C in air or low oxygen partial pressure, p(O2)[ and final heat treatment [at 850 °C in air or low p(O2)[ on preparation of BaTiO3 thin films were examined. An epitaxial BaTiO3 thin film with a dense and smooth surface consisting of nanosized grains about 70 nm was prepared by prefiring under low p(O2) at 250 °C and final heat treatment under low p (O2) at 850 °C.

Relationship Between Acid Intergranular Corrosion and Caustic Stress Corrosion Cracking of Alloy 600

CORROSION ◽  
1977 ◽  
Vol 33 (1) ◽  
pp. 20-26 ◽  
Author(s):  
G. J. THEUS
Keyword(s):  
Heat Treatment ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Alloy 600 ◽  
Intergranular Attack ◽  
Electrochemical Tests ◽  
Stress Relieving ◽  
Service Conditions ◽  
The Relationship

Abstract Modified Streicher and 288 C (550 F) electrochemical caustic stress corrosion tests were performed on Alloy 600 to determine the relationship between acid intergranular attack susceptibility and caustic stress corrosion cracking (SCC) susceptibility. Mill annealed and solution annealed materials with and without a subsequent 621 C (1150 F) heat treatment (simulated stress relief) were evaluated. Susceptibility to attack in the Streicher test was greatest for material that had received a 621 C (1150 F) heat treatment, whereas this heat treatment caused the same material to be least susceptible to cracking in the electrochemical tests. The conclusions drawn from these results are: (1) stress relieving Alloy 600 does improve its resistance to caustic SCC, and (2) resistance of Alloy 600 to acid intergranular attack does not imply resistance of Alloy 600 to caustic SCC. Therefore, the results demonstrate the need for selecting corrosion qualification tests which are relevant to service conditions.

Effects of Pre-Crack Depth and Hydrogen Absorption on the Failure Strain of Zircaloy-4 Cladding Tubes Under Biaxial Strain Conditions

2020 ◽  
Author(s):  
Feng Li ◽  
Takeshi Mihara ◽  
Yutaka Udagawa ◽  
Masaki Amaya
Keyword(s):  
Heat Treatment ◽  
Crack Depth ◽  
Strain Ratio ◽  
Final Heat Treatment ◽  
Fuel Cladding ◽  
Hoop Strain ◽  
Final Heat ◽  
Treatment Status ◽  
Biaxial Tensile Stress ◽  
Cold Worked

Abstract Fuel cladding may be subjected to biaxial tensile stress in axial and hoop directions during pellet-cladding mechanical interaction (PCMI) of a reactivity-initiated accident (RIA). Incipient crack in the hydride rim assisted by the scattered hydrides in the metal phase may lead to failure of the cladding at small hoop strain level during PCMI. To get insight of such phenomenon, biaxial-EDC tests under axial to hoop strain ratios ranging from 0 to 1 were performed with pre-cracked (outer surface) and uniformly hydrided Zircaloy-4 cladding tube samples with final heat-treatment status of cold worked (CW), stress relieved (SR) and Recrystallized (RX). Results showed dependencies of failure hoop strain on pre-crack depth, strain ratio, hydrogen content and final heat-treatment status on fabrication, but no apparent dependencies were observed on the distribution pattern of hydrides (with similar hydrogen contents and hydrides predominantly precipitated in hoop direction) and the heat-treatment process for hydrogen charging. J integral at failure seems to be available to unify the effect of pre-crack depth.

Effect of Cold Working and Heat Treatment on Stress Corrosion Cracking Behavior of Duplex Stainless Steel

1979 ◽  
Vol 65 (6) ◽  
pp. 617-626 ◽  
Author(s):  
Kikuo TAKIZAWA ◽  
Yasuhiko SHIMIZU ◽  
Eisaku YONEDA ◽  
Hokoto SHOJI ◽  
Imao TAMURA
Keyword(s):  
Heat Treatment ◽  
Stainless Steel ◽  
Stress Corrosion ◽  
Duplex Stainless Steel ◽  
Stress Corrosion Cracking ◽  
Cold Working ◽  
Corrosion Cracking ◽  
Cracking Behavior
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