scholarly journals Creep Rate, Friction, and Wear of Two Heat-Affected Zone Regions of 9–12 wt.% Cr Steels

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 558
Author(s):  
Igor Velkavrh ◽  
Joël Voyer ◽  
Fevzi Kafexhiu ◽  
Bojan Podgornik
Keyword(s):  
Creep Rate ◽  
Heat Affected Zone ◽  
Power Plants ◽  
Friction And Wear ◽  
Tribological Performance ◽  
Steel Matrix ◽  
Austenite Grain Size ◽  
P91 Steel ◽  
Cr Steels ◽  
Main Steam

Coarsening of precipitates can have a profound effect on the mechanical properties of martensitic 9–12 wt.% Cr steels, which are typically used in critical parts of fossil-fuel power plants such as turbines, headers, and main steam pipes. In the present study, changes in precipitates’ size and distribution in the simulated heat-affected zone of two different 9–12 wt.% Cr steels (X20 and P91) after different aging conditions were analyzed and correlated with their creep, friction, and wear behaviors. It was shown that prior to aging, the morphology of the steel matrix (prior austenite grain size and microstructure homogeneity) governed the creep rate and the tribological performance of both steels, while after aging their response was additionally determined by the combination of the number and the size of precipitates. For the selected samples (prepared under identical conditions), number of precipitates was found to be within a narrower range for the X20 steel as compared to the P91 steel. For both steels, aging for a shorter time at the higher temperature yielded significantly higher stationary creep rate values as compared to aging for longer time at the lower temperature. The increase was more pronounced in the P91 than in the X20 steel. Both prior to and after aging, the P91 steel typically provided slightly higher creep resistance than the X20 steel, while the latter provided slightly better tribological performance. Furthermore, as a function of the increasing number of precipitates, static coefficient of friction in air atmosphere was approximately linearly decreasing, while the wear rate initially decreased.

Oil-soluble ionic liquid to lubricate silicon

2021 ◽  
pp. 135065012098488
Author(s):  
Waleed Al-Sallami ◽  
Pourya Parsaeian ◽  
Abdel Dorgham ◽  
Anne Neville
Keyword(s):  
Ionic Liquid ◽  
High Temperature ◽  
Friction And Wear ◽  
Tribological Performance ◽  
Considerable Reduction ◽  
Zinc Dialkyldithiophosphate ◽  
Lubrication Mechanism ◽  
Wear Coefficient ◽  
Wear Performance ◽  
Micro Scale

Trihexyltetradecylphosphonium bis(2-ethylhexyl)phosphate (phosphonium phosphate) ionic liquid is soluble in non-polar lubricants. It has been proposed as an effective anti-wear additive comparable to zinc dialkyldithiophosphate. Previously, phosphonium phosphate has shown a better anti-wear performance under some conditions such as high temperature. In this work, the tribological performance and the lubrication mechanism of phosphonium phosphate are compared with that of zinc dialkyldithiophosphate when lubricating silicon under various tribological conditions. This can lead to an understanding of the reasons behind the superior anti-wear performance of phosphonium phosphate under some conditions. A micro-scale study is conducted using a nanotribometer. The results show that both additives lead to a considerable reduction in both friction and wear coefficients. The reduction in the wear coefficient is mainly controlled by the formation of the tribofilm on the rubbing surfaces. Zinc dialkyldithiophosphate can create a thicker tribofilm, which results in a better anti-wear performance. However, the formation of a thicker film will lead to a faster depletion and thus phosphonium phosphate can provide better anti-wear performance when the depletion of zinc dialkyldithiophosphate starts.

An Experimental Measurement of Toughness Locus for a Ductile Material

2005 ◽  
Vol 297-300 ◽  
pp. 2410-2415 ◽  
Author(s):  
Dong Hak Kim ◽  
Jeong Hyun Lee ◽  
Ho Dong Kim ◽  
Ki Ju Kang
Keyword(s):  
Crack Length ◽  
Nuclear Power ◽  
Power Plants ◽  
Test Procedure ◽  
Stress Triaxiality ◽  
Crack Tip ◽  
Potential Drop ◽  
Image Correlation ◽  
Ductile Material ◽  
Main Steam

A toughness locus Jc-Q for a ductile steel, SA106 Grade C used in the main steam piping of nuclear power plants, has been experimentally evaluated. Along with the standard fracture test procedure for J-R curve, Q as the second parameter governing stress triaxiality nearby the crack tip is measured from the displacements nearby the side necking which occurs near the crack tip on the lateral surface of a fracture specimen. The displacements nearby the side necking are measured from the digital images taken during the fracture experiment based on Stereoscopic Digital Photography (SDP) and high resolution Digital Image Correlation (DIC) software. The crack length is monitored by Direct Current Potential Drop (DCPD) method and the J-R curve is determined according to ASTM standard E1737-96. The effects of crack length, specimen geometry and thickness of specimen are studied, which are included in the toughness locus Jc-Q.

scholarly journals The influence of manual metal arc multiple repair welding of long operated waterwall on the structure and hardness of the heat affected zone of welded joints

2017 ◽  
Vol 62 (1) ◽  
pp. 327-333 ◽  
Author(s):  
J. Pikuła ◽  
M. Łomozik ◽  
T. Pfeifer
Keyword(s):  
Heat Affected Zone ◽  
Welded Joints ◽  
Arc Welding ◽  
Power Plants ◽  
Welded Joint ◽  
Weld Bead ◽  
Boiler Steel ◽  
Metallographic Examination ◽  
Metal Arc Welding ◽  
High Degree

Abstract Welded installations failures of power plants, which are often result from a high degree of wear, requires suitable repairs. In the case of cracks formed in the weld bead of waterwall, weld bead is removed and new welded joint is prepared. However, it is associated with consecutive thermal cycles, which affect properties of heat affected zone of welded joint. This study presents the influence of multiple manual metal arc welding associated with repair activities of long operated waterwall of boiler steel on properties of repair welded joints. The work contains the results of macro and microscopic metallographic examination as well as the results of hardness measurements.

A review on tribological performance of ionic liquids as additives to bio lubricants

2020 ◽  
pp. 135065012097380
Author(s):  
Tehreem Naveed ◽  
Rehan Zahid ◽  
Riaz Ahmad Mufti ◽  
Muhammad Waqas ◽  
Muhammad Talha Hanif
Keyword(s):  
Ionic Liquids ◽  
Friction And Wear ◽  
Combustion Engine ◽  
Tribological Performance ◽  
Environmental Concerns ◽  
Published Data ◽  
Oil Reserves ◽  
Mineral Oils ◽  
The Past ◽  
Interacting Surfaces

All the moving components in an internal combustion engine require a lubricant that allows smooth sliding and/or rolling of interacting surfaces. Lubricant not only minimizes the friction and wear but also dissipates the heat generated due to friction and removes debris from the area of contact. Environmental concerns, decreasing mineral oil reserves and difficult disposal of nonbiodegradable conventional lubricants have urged the researchers to shift towards environmental-friendly lubricants. Number of tribological studies carried out in the past have proved that ionic liquid-based bio-lubricants are sustainable and biodegradable alternative to mineral oils. This paper presents a brief review of properties of ionic liquids and their ability to reduce friction and wear between the interacting surfaces. Tribological performance and compatibility of ionic liquids with various base-oils have been compared under boundary lubrication. The results reveal that phosphonium-based ionic liquids namely tetra-decyl tri-hexyl phosphonium bis(2,4,4-trimethylpentyl) phosphinate (P66614)i(C8)2PO2 and tri-hexyl tetra-decyl phosphonium bis(2-ethylhexyl) phosphate (P-DEHP) are more suitable for tribological applications. Since, ionic liquids can be tailored according to the application and millions of combinations are possible therefore, there is a need to summarize the published data in a more systematic and logical way.

scholarly journals The Microstructure and Property of the Heat Affected zone in C-Mn Steel Treated by Rare Earth

2019 ◽  
Vol 38 (2019) ◽  
pp. 362-369 ◽  
Author(s):  
Ming-ming Song ◽  
Yu-min Xie ◽  
Bo Song ◽  
Zheng-liang Xue ◽  
Nan Nie ◽  
...  
Keyword(s):  
Rare Earth ◽  
Impact Toughness ◽  
Heat Affected Zone ◽  
Acicular Ferrite ◽  
Steel Matrix ◽  
Impact Properties ◽  
Treated Steel ◽  
The Impact ◽  
Welding Processes ◽  
Mn Steel

AbstractThe microstructures and impact properties of the heat affected zone (HAZ) in steel treated by rare earth (RE) under different welding processes were discussed. The effect of Al on the impact properties of the HAZ in RE treated steel was analyzed. It finds that when the welding t8/5 is smaller than 111 s, the main microstructure in steels is bainite/widmanstatten. The impact toughness of the HAZ is lower than that of the steel matrix. When t8/5 is more than 250 s, the microstructure is mainly acicular ferrite (AF) in the steel treated by RE, and the impact toughness of HAZ is obviously improved. Even under the welding processing with t8/5 about 600 s in RE treated steel can still obtain a lot of AF. While in the steel killed by Al and treated by RE, the main microstructure is parallel cluster of bainite/widmanstatten, and the impact toughness of HAZ is significantly lower than that of low-Al RE treated steel. Al can deteriorate the optimizing of RE treatment on HAZ.

scholarly journals Tribological Performance Optimization of Al-7.5% SiCp Composites Using the Taguchi Method and Grey Relational Analysis

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Shouvik Ghosh ◽  
Prasanta Sahoo ◽  
Goutam Sutradhar
Keyword(s):  
Taguchi Method ◽  
Metal Matrix Composite ◽  
Matrix Composite ◽  
Grey Relational Analysis ◽  
Metal Matrix ◽  
Friction And Wear ◽  
Tribological Performance ◽  
Relational Analysis ◽  
Test Parameters ◽  
Grey Relational

The present study considers an experimental study of tribological performance of Al-7.5% SiCp metal matrix composite and optimization of tribological testing parameters based on the Taguchi method coupled with grey relational analysis. A grey relational grade obtained from grey relational analysis is used as a performance index to study the behaviour of Al-7.5% SiCp MMC with respect to friction and wear characteristics. The tribological experiments are carried out by utilizing the combinations of tribological test parameters based on the L27 Taguchi orthogonal design with three test parameters, namely, load, speed, and time. The material Al-7.5% SiCp metal matrix composite is developed by reinforcing LM6 aluminium alloy with 7.5% (by weight) SiC particle of 400 mesh size (~37 μm) in an electric melting furnace. It is observed that sliding time has a significant contribution in controlling the friction and wear behaviour of Al-7.5% SiCp MMC. Furthermore, all the interactions between the parameters have significant influence on tribological performance. A confirmation test is also carried out to verify the accuracy of the results obtained through the optimization problem. In addition, a scanning electron microscopy (SEM) test is performed on the wear tracks to study the wear mechanism.

Competitive Bidding by Surrogate Modeling of Steam Parameter Influence on the Attainable Start Numbers of Turbine Casings

2020 ◽  
Author(s):  
Marcel Seiler ◽  
Vitali Züch ◽  
Peter Dumstorff ◽  
Henning Almstedt
Keyword(s):  
Wall Temperature ◽  
Surrogate Model ◽  
Power Plants ◽  
Fe Model ◽  
Steam Turbines ◽  
Require Time ◽  
Steam Parameters ◽  
Fast Prediction ◽  
Main Steam ◽  
Flexible Operation

Abstract The continued expansion of fluctuating energy sources such as wind turbines and solar systems will increase the demand for more flexible operation modes of power plants. Especially steam turbines with all their components will have to sustain a higher amount of start-stop cycles in order to compensate for variations in wind and solar radiation. Besides the rotor, inner casings are an example for main steam turbine components which are strongly loaded by thermal cycles at each start and shut down procedure. A precise prediction of the attainable number of start-stop cycles enables a more flexible operation within the guaranteed lifetime. However, this would require time-consuming FE calculations for each power plant due to their specific steam parameters. In this paper, a physics based surrogate model is discussed for a fast prediction of permissible start-stop cycles at plant specific steam parameters. The correlation between the physical properties from the surrogate model (wall temperature difference and the resulting stresses) and the attainable number of start-stop cycles from the FE model is determined. A validation with a different inner casing design within a usual wall temperature range confirms the high accuracy level of the surrogate model compared to uncertainties like material scatter or casting tolerances. With the provided approach typically a higher number of starts can be efficiently calculated in the bidding phase compared to assuming only one conservative value for each turbine type or size. Furthermore, the steam parameters can be optimized for increasing the number of starts to the required value without additional and time-consuming FE calculations.

scholarly journals Effect of Cold Working on the Driving Force of the Crack Growth and Crack Growth Rate of Welded Joints under One Overload

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Hongliang Yang ◽  
He Xue ◽  
Fuqiang Yang ◽  
Shuai Wang
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Creep Rate ◽  
Crack Growth ◽  
Heat Affected Zone ◽  
Driving Force ◽  
Cold Working ◽  
Crack Tip ◽  
Simulation Method ◽  
Fusion Line

To understand the effect of cold working of welding heat-affected zone on the driving force of the crack growth and crack growth rate of stress corrosion cracking (SCC) near the welding fusion line, the finite element simulation method was used to analyze the effect of cold working on the tensile stress of the crack tip at different locations near the fusion line. On this basis, the strain rate of the crack tip in the Ford-Andresen model is replaced by the creep rate of the crack tip, and the creep rate of the crack tip is used as driving force for the crack growth of SCC. The effect of the cold working level at the heat-affected zone on the driving force of the crack growth and crack growth rate of SCC are analyzed, and driving force of the crack growth and crack growth rate of SCC after one overload was compared.

scholarly journals Elastoplastic Fracture Analysis of the P91 Steel Welded Joint under Repair Welding Thermal Shock Based on XFEM

Metals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1285 ◽  
Author(s):  
Kai Yang ◽  
Yingjie Zhang ◽  
Jianping Zhao
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Thermal Shock ◽  
Power Plants ◽  
Welded Joint ◽  
Welding Process ◽  
Simulation Method ◽  
Fracture Analysis ◽  
P91 Steel ◽  
Repair Welding

P91 steel is a typical steel used in the manufacture of boilers in ultra-supercritical power plants and heat exchangers in nuclear power plants. For the long-term serviced P91 steel pressurized structures, the main failure mode is the welded joint failure, especially the heat affected zone (HAZ) failure. Repair welding technique is an effective method for repairing such local defects. However, the thermal shock composed of high temperature and thermal stress in the repair welding process will pose a critical loading condition for the existing defects near the heat source which cannot be detected by conventional means. So, the evaluation of structural integrity for the welded joint in the thermal-mechanical coupling field is necessary. In this work, the crack propagation law in the HAZ for the P91 steel welded joint was investigated under repair welding thermal loads. The weld repair model of the P91 steel welded joint was established by ABAQUS. The transient temperature field and stress field in repair welding process were calculated by relevant user subroutines and sequential coupling simulation method. The residual stress was determined by the impact indentation strain method to verify the feasibility of the finite element (FE) model and simulation method. In order to obtain the crack propagation path, the elastoplastic fracture analysis of the welded joint with initial crack was performed based on the extended finite element method (XFEM). The influence of different welding linear energy on the crack propagation was analyzed. The results show that the cracks in the HAZ propagate perpendicular to the surface and tend to deflect to the welding seam under repair welding thermal loads. The crack propagation occurs in the early stage of cooling. Higher welding linear energy leads to larger HAZ and higher overall temperature. With the increase of welding linear energy, the length and critical distance of the crack propagation increase. Therefore, low welding linear energy can effectively inhibit the crack propagation in the HAZ. The above calculation and analysis provide a reference for the thermal shock damage analysis of repair welding process, which is of great significance to improving the safety and reliability of weld repaired components.

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