Effect of Long-Term Annealing on the Impact Toughness of 22K Steel

2021 ◽  
Vol 2021 (4) ◽  
pp. 481-485
Author(s):  
S. A. Nikulin ◽  
S. O. Rogachev ◽  
S. G. Vasil’ev ◽  
V. A. Belov ◽  
A. A. Komissarov
Keyword(s):  
Materials ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6076
Author(s):  
Ladislav Falat ◽  
Lucia Čiripová ◽  
Viera Homolová ◽  
Miroslav Džupon ◽  
Róbert Džunda ◽  
...  

In this work, the effects of various conditions of short-term rejuvenation heat treatment on room-temperature mechanical properties of long-term aged P92 boiler steel were investigated. Normalized and tempered P92 steel pipe was thermally exposed at 600 °C for time durations up to 5000 h in order to simulate high-temperature material degradation, as also occurring in service conditions. Thus, thermally embrittled material states of P92 steel were prepared, showing tempered martensitic microstructures with coarsened secondary phase precipitates of Cr23C6-based carbides and Fe2W-based Laves phase. Compared with the initial normalized and tempered material condition, thermally aged materials exhibited a slight decrease in strength properties (i.e., yield stress and ultimate tensile strength) and deformation properties (i.e., total elongation and reduction of area). The hardness values were almost unaffected, whereas the impact toughness values showed a steep decrease after long-term ageing. An idea for designing the rejuvenation heat treatments for restoration of impact toughness was based on tuning the material properties by short-term annealing effects at various selected temperatures somewhat above the long-term ageing temperature of P92 material. Specifically, the proposed heat treatments were performed within the temperature range between 680 °C and 740 °C, employing variable heating up and cooling down conditions. It was revealed that short-term annealing at 740 °C for 1 h with subsequent rapid cooling into water represents the most efficient rejuvenation heat treatment procedure of thermally aged P92 steel for full restoration of impact toughness up to original values of normalized and tempered material state. Microstructural observations clearly indicated partial dissolution of the Laves phase precipitates to be the crucial phenomenon that played a key role in restoring the impact toughness.


2012 ◽  
Vol 706-709 ◽  
pp. 2211-2216
Author(s):  
Ilya Nikulin ◽  
Rustam Kaibyshev

The interrelations between microstructure, precipitation and mechanical properties of the 18Cr-8Ni-W-Nb-V-N austenitic stainless steel were examined under long-term aging at 650°C. It was shown that aging leads to decreasing strength characteristics with increasing aging time despite the fact that hardness tends to increase. In none-aged condition the present steel exhibits superior impact toughness of about 255 J/cm-2. This values decreases gradually at the early stage of the aging. After 1000 hours exposure the impact toughness is 195 J/cm-2 and decreases sharply to 135 J/cm-2 at 3000 hours. However, an evidence for ductile fracture was found even after long-term aging. Degradation in impact toughness and mechanical properties with aging is discussed in relation to microstructure evolution, precipitations of the secondary phase and fracture mechanisms.


2021 ◽  
Vol 51 (7) ◽  
pp. 428-437
Author(s):  
S. A. Nikulin ◽  
S. O. Rogachev ◽  
V. A. Belov ◽  
A. A. Komissarov ◽  
V. Yu. Turilina ◽  
...  

Metals ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 3
Author(s):  
Alexandra Fedoseeva ◽  
Ivan Nikitin ◽  
Nadezhda Dudova ◽  
John Hald ◽  
Rustam Kaibyshev

This paper presents the results of an experimental investigation of a 12% Cr steel where a significant increase in Charpy impact toughness and a slight decrease in ductile-brittle transition temperature (DBTT) from 70 °C to 65 °C were obtained through thermo-mechanical processing, including interim hot forging at 1050 °C with long-term annealing at 1000 °C, as compared with conventional heat treatment. At lower temperatures ranging from −20 °C to 25 °C, the value of impact toughness comprised ~40 J cm−2 in the present 12% Cr steel subjected to thermo-mechanical processing. The amount of δ-ferrite decreased to 3.8%, whereas the size of prior austenite grains did not change and comprised about 40–50 μm. The boundaries between δ-ferrite and martensitic laths were decorated by continuous chains of Cr- and W-rich carbides. M23C6 carbides also precipitated along the boundaries of prior austenite grains, packets, blocks and martensitic laths. Thermo-mechanical processing increased the mean size of M23C6 carbides and decreased their number particle densities along the lath boundaries. Moreover, the precipitation of a high number of non-equilibrium V-rich MX particles was induced by hot forging and long-term normalizing at 1000 °C for 24 h.


2014 ◽  
Vol 627 ◽  
pp. 205-208
Author(s):  
Mattias Calmunger ◽  
Guo Cai Chai ◽  
Sten Johansson ◽  
Johan Moverare

Structural integrity is crucial for the safety of power plants with higher efficiency to meet the increasing global energy consumption. High-temperature environment will demand not only improved high-temperature corrosion resistance but also a maintained sufficient toughness. This study investigates how long term high-temperature environment influence the impact toughness of two austenitic stainless steels (AISI 304 and Sandvik SanicroTM 28) and one nickel-bas alloy (Alloy 617). Alloy 617 has shown increasing impact toughness with both increasing temperature and time, up to 700°C and 3 000 hours, while the two austenitic stainless steels have shown the opposite for the same conditions. At 10 000 hours the impact toughness of Alloy 617 has decreased but the alloy still possess great toughness. Both austenitic stainless steels show embrittlement due to brittle σ-phase and Alloy 617 seems to gain good impact toughness performance from small evenly distributed precipitates.


2011 ◽  
Vol 70 (1) ◽  
pp. 5-11 ◽  
Author(s):  
Beat Meier ◽  
Anja König ◽  
Samuel Parak ◽  
Katharina Henke

This study investigates the impact of thought suppression over a 1-week interval. In two experiments with 80 university students each, we used the think/no-think paradigm in which participants initially learn a list of word pairs (cue-target associations). Then they were presented with some of the cue words again and should either respond with the target word or avoid thinking about it. In the final test phase, their memory for the initially learned cue-target pairs was tested. In Experiment 1, type of memory test was manipulated (i.e., direct vs. indirect). In Experiment 2, type of no-think instructions was manipulated (i.e., suppress vs. substitute). Overall, our results showed poorer memory for no-think and control items compared to think items across all experiments and conditions. Critically, however, more no-think than control items were remembered after the 1-week interval in the direct, but not in the indirect test (Experiment 1) and with thought suppression, but not thought substitution instructions (Experiment 2). We suggest that during thought suppression a brief reactivation of the learned association may lead to reconsolidation of the memory trace and hence to better retrieval of suppressed than control items in the long term.


2003 ◽  
Author(s):  
Teresa Garate-Serafini ◽  
Jose Mendez ◽  
Patty Arriaga ◽  
Larry Labiak ◽  
Carol Reynolds

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