On the microstructural origin of premature failure of creep strength enhanced martensitic steels

2021 ◽  
Vol 87 ◽  
pp. 269-279
Author(s):  
J. Li ◽  
C. Xu ◽  
G. Zheng ◽  
W.J. Dai ◽  
C.C. Bu ◽  
...  
Keyword(s):  
Creep Strength ◽  
Martensitic Steels ◽  
Premature Failure

Effect of Intermittent Heating on Creep Behaviour of Advanced 9-12%Cr Power Plant Steels

2007 ◽  
Vol 561-565 ◽  
pp. 81-84 ◽  
Author(s):  
Vàclav Sklenička ◽  
Květa Kuchařová ◽  
Milan Svoboda ◽  
Ivan Saxl
Keyword(s):  
Creep Strength ◽  
Creep Behaviour ◽  
Laboratory Simulation ◽  
Dislocation Creep ◽  
Martensitic Steels ◽  
Significant Deterioration ◽  
Start Up ◽  
Creep Characteristics ◽  
Intermittent Heating ◽  
High Temperature Components

Critical high temperature components of machines and structures are often subjected to complicated load and temperature histories. The closest laboratory simulation of service loading conditions involves creep under nonsteady temperatures and stresses. For example, the start up and shut down cycles can be well simulated by temperature variation by use of intermittent heating tests. Such approach is illustrated by recent experimental results on advanced high creep strength 9- 12%Cr ferritic-martensitic steels (P91, P92 and E911). A comparison between the creep characteristics of nonsteady and monotonously creep specimens has revealed no significant deterioration of the creep strength and fracture resistance of these steels in power-law (dislocation) creep.

scholarly journals Manufacture and Performance of Welds in Creep Strength Enhanced Ferritic Steels

Materials ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2257 ◽  
Author(s):  
Jonathan Parker ◽  
John Siefert
Keyword(s):  
Creep Strength ◽  
High Energy ◽  
Alternative Methods ◽  
Main Body ◽  
Martensitic Steels ◽  
Worst Case ◽  
Factors Affecting ◽  
Energy Applications ◽  
And Performance ◽  
Critical Components

Welding is a vital process required in the fabrication of ‘fracture critical’ components which operate under creep conditions. However, often the procedures used are based on ‘least initial cost’. Thus, it is not surprising that in many high energy applications, welds are the weakest link, i.e., damage is first found at welds. In the worst case, weld cracks reported have had catastrophic consequences. Comprehensive Electric Power Research Institute (EPRI) research has identified and quantified the factors affecting the high temperature performance of advanced steels working under creep conditions. This knowledge has then been used to underpin recommendations for improved fabrication and control of creep strength enhanced ferritic steel components. This review paper reports background from this work. The main body of the review summarizes the evidence used to establish a ‘well engineered’ practice for the manufacture of welds in tempered martensitic steels. Many of these alternative methods can be applied in repair applications without the need for post-weld heat treatment. This seminal work thus offers major benefits to all stakeholders in the global energy sector.

The Role of Microstructure in Creep Strength of 9-12%Cr Steels

2016 ◽  
Vol 879 ◽  
pp. 36-41 ◽  
Author(s):  
Rustam Kaibyshev ◽  
Roman Mishnev ◽  
Alexandra Fedoseeva ◽  
Nadezhda Dudova
Keyword(s):  
Creep Strength ◽  
Ostwald Ripening ◽  
Vital Role ◽  
Laves Phase ◽  
Lattice Dislocation ◽  
High Threshold ◽  
Subgrain Structure ◽  
Martensitic Steels ◽  
Ferritic Matrix ◽  
Static Recovery

Tempered martensite lath structure (TMLS) plays a vital role in creep resistance of high chromium martensitic steels. Under creep conditions the TMLS could be stabilized by three agents: (i) a dispersion of boundary M23C6 carbides and Laves phase; (ii) a dispersion of M(C,N) carbonitrides, which are homogeneously distributed within ferritic matrix; (iii) substitutional alloying element within ferritic matrix. The boundary particles exert a large Zener drag force which effectively hinders migration of low-and high-angle boundaries. A dispersion of M(C,N) carbonitrides both within ferritic matrix and lath boundaries provides the pinning of mobile dislocations. This process is responsible for reliving long-range elastic stress field originated from lath boundaries. In addition, M(C,N) carbonitrides provide high threshold stress. Substitutional elements as W and Mo effectively slowing down diffusion in ferritic matrix retard climb of lattice dislocation that also prevents the aforementioned knitting reaction. The suppression of knitting reaction between lattice dislocation and low-angle boundaries prevents their transformation to subboundaries by concurrent operation of all three agent types. Depletion of W and Mo from solid solution leads to the occurrence of static recovery and precipitation of Laves phase at boundaries under long-term aging. This process is responsible for creep strength breakdown. The strain-induced formation of Z-phase at the expense of V-rich M(C,N) carbonitrides highly facilitates this process. However, slow strain-induced coarsening of M23C6 carbides and M(C,N) carbonitrides provides the suppression of the knitting reaction between mobile lattice dislocations and intrinsic dislocations of lath boundaries and replacement of TMLS by subgrain structure. Ostwald ripening of boundary M23C6 carbides and Laves phase leads to rapid creep rate increase with strain in tertiary creep and premature rupture owing to the formation of subgrain structure replaced TMLS and further subgrain growth.

Optimisation of long-term creep strength of martensitic steels

2010 ◽  
Vol 63 (2-3) ◽  
pp. 357-361 ◽  
Author(s):  
F. Kauffmann ◽  
K. Maile ◽  
S. Straub ◽  
K. H. Mayer ◽  
M. Bauer ◽  
...  
Keyword(s):  
Creep Strength ◽  
Martensitic Steels ◽  
Term Creep

Research and Modelling on Electrical and Thermal Mode of LEDs Operation in the Luminaire

2018 ◽  
pp. 155-162 ◽  
Author(s):  
Sergei S. Kapitonov ◽  
Anastasia V. Kapitonova ◽  
Sergei Yu. Grigorovich ◽  
Sergei A. Medvedev ◽  
Taher Sobhy
Keyword(s):  
Thermal Conditions ◽  
Operating Mode ◽  
Thermal Processes ◽  
Thermal Mode ◽  
Crystal Temperature ◽  
Premature Failure ◽  
Model Based

In the article, the electrical and thermal processes in the LED lamp with varied parameters are investigated. Voltage and current measurements on all LEDs of the luminaire are carried out in the nominal operating mode. The power allocated to each LED is determined. The calculation of the LED crystal temperature was carried out using the developed thermal LED model based on the results of the measurements and by using “Multisim” program. It has been established that the temperature of the crystals of individual LEDs in the luminaire differ significantly, which leads to unfavourable thermal conditions for them and an increased likelihood of premature failure.

Rubber Fracture Characterization Using J-Integral

1988 ◽  
Vol 16 (1) ◽  
pp. 44-60 ◽  
Author(s):  
C. L. Chow ◽  
J. Wang ◽  
P. N. Tse
Keyword(s):  
Crack Initiation ◽  
Carbon Black ◽  
Natural Rubber ◽  
Fracture Parameter ◽  
J Integral ◽  
Specimen Length ◽  
Fracture Characterization ◽  
Premature Failure ◽  
Testing Procedures ◽  
Material Evaluation

Abstract The use of the J-integral to investigate fracture characterization in a carbon black reinforced natural rubber is described. Three applications to crack initiation are included: two based on the use of a hypothetical zero specimen length and one on conventional testing procedures for metals. While the validity of the zero-length methods is questionable, the conventional method yielded a consistent Jc value of 1.01 N/mm for a typical tire compound. This value was obtained from 24 combinations of varying specimen geometries and pre-crack lengths. The J-integral is revealed as a valid fracture parameter that is applicable not only for material evaluation but also for designing tire structures to resist premature failure. These conclusions disagree with those from an earlier investigation, so the causes for the discrepancies are examined and discussed.

FANSTEEL 85 METAL

Alloy Digest ◽  
1981 ◽  
Vol 30 (6) ◽  
Keyword(s):  
High Temperature ◽  
Physical Properties ◽  
Creep Strength ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Base Alloy ◽  
Heat Treating ◽  
Good Combination ◽  
Bend Strength ◽  
Temperature Performance

Abstract FANSTEEL 85 METAL is a columbium-base alloy characterized by good fabricability at room temperature, good weldability and a good combination of creep strength and oxidation resistance at elevated temperatures. Its applications include missile and rocket components and many other high-temperature parts. This datasheet provides information on composition, physical properties, microstructure, hardness, elasticity, tensile properties, and bend strength as well as creep. It also includes information on low and high temperature performance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: Cb-7. Producer or source: Fansteel Metallurgical Corporation. Originally published December 1963, revised June 1981.

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