Effect of Microstructure on Mechanical Behavior of a Combined Steam Turbine Rotor Steel

Zhu, Ming‐Liang; Linbo, Mei; Xuan, Fu‐Zhen

doi:10.1115/gt2015-44132

Cited by 3 publications

(2 citation statements)

References 12 publications

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“…The rotor shafts for power plant equipment undergo changes in their microstructure as a result of long-term operation. To keep them in good working order, it is necessary to carry out comprehensive diagnostic measures that may include the following technical procedures: (a) non-destructive testingultrasonic, eddy current, and magnetic particle flaw detection is used to detect surface and subsurface defects in rotor shafts [24][25][26][27]; and (b) a microstructural analysis [28][29][30][31][32][33][34][35].…”

Section: Literature Survey: State-of-the-artmentioning

confidence: 99%

Hydrogen Cooling of Turbo Aggregates and the Problem of Rotor Shafts Materials Degradation Evaluation

Balitskii,

Syrotyuk,

Havrilyuk

et al. 2023

Energies

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Changes in the properties of 38KhN3MFA steel, from which the rotor shaft is made, were investigated by comparing the hardness of the shaft surface and hydrogen concentration in the chips and analyzing changes in the morphology of the chips under the influence of various factors. The microstructures obtained from the surface of the rotor shaft samples are presented, and histograms reflecting the parameters of the structural components are constructed. An abbreviated diagram of the “life cycle” of the turbine rotor shaft is given. It was found that, during long-term operation (up to 250 thousand hours), the hardness of the rotor shaft surface decreases from 290 HB to 250 HB. It was recorded that, in the microstructure of the shaft during 250 thousand hours of operation, the amount of cementite decreased from 87% to 62%, and the proportion of free ferrite increased from 5% to 20%. The average values of ferrite microhardness decreased from 1.9 GPa to 1.5 GPa. An increase in the content of alloying elements in carbides was recorded: Cr and V—by 1.15–1.6 times; and Mo—by 2.2–2.8 times. With the help of the developed program (using computer vision methods), changes in their microrelief were detected to study photos of chips.

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Section: Literature Survey: State-of-the-artmentioning

confidence: 99%

Hydrogen Cooling of Turbo Aggregates and the Problem of Rotor Shafts Materials Degradation Evaluation

Balitskii,

Syrotyuk,

Havrilyuk

et al. 2023

Energies

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“…26NiCrMoV10-10 medium carbon low alloy steels are widely used in power plants as the hot forged industrial parts because of its excellent high temperature strength. 1,2 However, its wear resistance property is poor, which affects its service life greatly. In order to overcome this disadvantage, surface treatment technology is conducted to the component.…”

Section: Introductionmentioning

confidence: 99%

Evolution of residual stresses in dissimilar steel surfacing layers during process of post-weld heat treatment

Wang

Lü

Gong

2013

Science and Technology of Welding and Joining

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Residual stress relaxation during post-weld heat treatment (PWHT) is a thermodynamic process, which is affected not only by the heat treatment process, but also by the welding residual stress. In this study, the residual stresses in as welded and heat treated surfacing metal were measured using blind hole and X-ray method. The results reveal that the welding residual stresses are compressive at the surface of the weld and tensile at inner weld. However, after PWHT, the residual stresses at surface and inner weld change to the opposite state. Finite element simulations show that the differences of expansion coefficients between base metal and filler material are the main factor to the changes of stress state. The experimental results verify that the expansion coefficients of base metal and filler materials have been changed greatly after long soaking at high temperature.

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Effects of Grain and Grain Boundary Elongation on Creep Crack Growth Using Virtual Test Model of Compact Tension Specimens

Hu¹,

Wang²,

et al. 2023

Advances in Accelerated Testing and Predictive Methods in Creep, Fatigue, and Environmental Cracking

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Understanding the creep failure mechanism depends on identifying the effects of applied load on the evolution of long-term microstructures. Creep tests at elevated temperatures are time consuming and expensive. Thus, it is important to optimize the number of tests needed to reduce the time from the fabrication of new materials to the operation cycle, as well as to extend materials application scenarios. This paper develops a grain/grain boundary microstructure meshing system in compact tension (CT) geometry that is extended to nonequiaxed grains. The model can produce elongated grains and grain boundaries to simulate the columnar grains in material. A continuum remaining multiaxial ductility damage mechanics model (known as a Nikbin, Smith and Webster [NSW] model) is then adopted to simulate the mechanics of creep behavior. Triple intersections of grain boundaries are invariably the weakest points that form voids to allow for microcracks to join and form macrocracks. The cracking is allowed to develop freely from an element following a critical multiaxial strain accumulation limit. The overall trend is that a loading direction perpendicular to the grain elongation direction contributes to slower creep cracking. This paper shows that it is possible to use grain-level finite element method (FEM) modeling to predict grain microstructure sensitivity to creep crack growth. This novel, virtual test method can be developed further using more complex microstructures to assist in quantifying cracking rates and reducing the number of actual tests needed to characterize crack growth in new materials.

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Effect of Microstructure on Mechanical Behavior of a Combined Steam Turbine Rotor Steel

Cited by 3 publications

References 12 publications

Hydrogen Cooling of Turbo Aggregates and the Problem of Rotor Shafts Materials Degradation Evaluation

Hydrogen Cooling of Turbo Aggregates and the Problem of Rotor Shafts Materials Degradation Evaluation

Evolution of residual stresses in dissimilar steel surfacing layers during process of post-weld heat treatment

Effects of Grain and Grain Boundary Elongation on Creep Crack Growth Using Virtual Test Model of Compact Tension Specimens

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