Impact Toughness for PM HIP 316L at Cryogenic Temperatures

2016 ◽  
Author(s):  
Tomas Berglund ◽  
Martin Östlund
Keyword(s):  
Grain Size ◽  
Impact Toughness ◽  
Oxygen Content ◽  
Room Temperature ◽  
Hot Isostatic Pressing ◽  
Cryogenic Temperatures ◽  
Inclusion Content ◽  
Conventional Material ◽  
The Impact ◽  
Suggested Explanation

It is well known throughout the PM HIP (Powder Metallurgy Hot Isostatic Pressing) industry that PM HIPed 316L material in general exhibit higher strength than conventional 316L. However, previous studies have shown an uncharacteristic behavior in impact toughness properties at cryogenic temperatures compared to conventional forged material. The uncharacteristic behavior consists of unexpectedly large drop in impact toughness at cryogenic temperatures which is not seen in the same extent in conventional material e.g. forged 316L. With the recent code case approval for PM HIPed 316L material, this behavior can be seen as an uncertainty regarding the performance of the material and its use in nuclear applications can therefore become limited. The behavior and underlying mechanisms is yet to be explained in detail. One possible explanation is that it is caused by oxides in the material, of which a large amount originates from oxygen picked up by the very large surface area of the powder during the manufacturing process. The correlation between impact toughness at room temperature and oxygen content is often referred to. In this study the non-metallic inclusion content is correlated to the impact properties at −196°C (−321°F), and a suggested explanation for the behavior of PM HIP 316L/316LN vs. conventional 316L is presented. The size and number of inclusions constitutes a major difference between the PM HIPed and conventional material. The results show that the size of the inclusions is significantly smaller in the PM materials compared to the conventional material and as a consequence they are present in larger numbers in the PM materials. Furthermore, the results clearly show the correlation between inclusion content and the impact toughness at cryogenic temperatures. The correlation is not as clear at room temperature where the different materials behave more similar. The suggested explanation is further supported by literature on cryogenic properties of 316L/316LN, 316L weld material and PM HIP 316LN with greatly reduced oxygen content. The impact toughness testing was performed using instrumented test equipment capable of recording load vs. displacement during testing. From this data the crack propagation and crack initiation energy can be estimated. Furthermore, it is known that grain size can influence mechanical properties. In this study no clear relationship between impact toughness and grain size could be observed. However, a correlation between the grain size and the amount of inclusions in the material was observed. It was found that larger amounts of inclusions in the PM HIPed material are correlated to a finer grain size. The results indicate that the inclusion particles inhibit grain growth during the HIP and heat treatment process by pinning of grain boundaries.

Effects of oxygen content on microstructure and impact toughness of high heat input flux-cored wire weld metals

2018 ◽  
Vol 115 (4) ◽  
pp. 410
Author(s):  
Fengyu Song ◽  
Yanmei Li ◽  
Ping Wang ◽  
Fuxian Zhu
Keyword(s):  
Grain Size ◽  
Impact Toughness ◽  
Weld Metal ◽  
Oxygen Content ◽  
Heat Input ◽  
High Heat ◽  
Cored Wire ◽  
Weld Metals ◽  
High Heat Input ◽  
The Impact

Three weld metals with different oxygen contents were developed. The influence of oxygen contents on the microstructure and impact toughness of weld metal was investigated through high heat input welding tests. The results showed that a large number of fine inclusions were formed and distributed randomly in the weld metal with oxygen content of 500 ppm under the heat input condition of 341 kJ/cm. Substantial cross interlocked acicular ferritic grains were induced to generate in the vicinity of the inclusions, primarily leading to the high impact toughness at low temperature for the weld metal. With the increase of oxygen content, the number of fine inclusions distributed in the weld metal increased and the grain size of intragranular acicular ferrites decreased, which enhanced the impact toughness of the weld metal. Nevertheless, a further increase of oxygen content would contribute to a great diminution of the austenitic grain size. Following that the fraction of grain boundary and the start temperature of transformation increased, which facilitated the abundant formation of pro-eutectoid ferrites and resulted in a deteriorative impact toughness of the weld metal.

Effect of Sintering Temperature on Structure and Dielectric Properties of Lead Free K0.5Na0.5NbO3 Prepared via Hot Isostatic Pressing

2017 ◽  
Vol 888 ◽  
pp. 42-46 ◽  
Author(s):  
Fatin Khairah Bahanurdin ◽  
Julie Juliewatty Mohamed ◽  
Zainal Arifin Ahmad
Keyword(s):  
Grain Size ◽  
Dielectric Properties ◽  
Room Temperature ◽  
Sintering Temperature ◽  
Hot Isostatic Pressing ◽  
Solid State Reaction Method ◽  
Lead Free ◽  
Tangent Loss ◽  
Isostatic Pressing ◽  
Tan Δ

In this research, alkaline niobate known as K0.5Na0.5NbO3 (KNN) lead-free piezoelectric ceramic was synthesis by solid state reaction method which pressing at different sintering temperatures (1000 °C and 1080 °C) prepared via hot isostatic pressing (HIP)). The effect of sintering temperature on structure and dielectric properties was studied. The optimum sintering temperature (at 1080 °C for 30 minutes) using hot isostatic pressing (HIP) was successfully increase the density, enlarge the particle grain size in the range of 0.3 µm – 2.5 µm and improves the dielectric properties of K0.5Na0.5NbO3 ceramics. The larger grain size and higher density ceramics body will contribute the good dielectric properties. At room temperature, the excellent relative permittivity and tangent loss recorded at 1 MHz (ɛr = 5517.35 and tan δ = 0.954), respectively for KNN1080HIP sample. The KNN1080HIP sample is also exhibits highest relative density which is 4.485 g/cm3. The ɛr depends upon density and in this work, the density increase as the sintering temperature increase, which resulting the corresponding ɛr value also increases.

Fracture Mechanics of Y2O3 Ceramics at High Temperatures

2014 ◽  
Vol 89 ◽  
pp. 88-93
Author(s):  
Marek Boniecki ◽  
Zdzislaw Librant ◽  
Władysław Wesołowski ◽  
Magdalena Gizowska ◽  
Marcin Osuchowski ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Grain Size ◽  
High Temperature ◽  
Fracture Mechanics ◽  
High Purity ◽  
Room Temperature ◽  
Bending Strength ◽  
Hot Isostatic Pressing ◽  
Temperature Changes ◽  
Four Point Bending

Fracture toughness KIc and four-point bending strength σc at high temperature (up to 1500 °C) of Y2O3 ceramics of various grain size were measured. The ceramics were prepared by pressureless air sintering and next hot isostatic pressing of high purity (99.99%) Y2O3 powder. Relative density of about 99 % was achieved. Photos of microstructures revealed small pores distributed mainly inside grains. For smallest grain size (2 - 9 μm) ceramics KIc and σc are almost constant from 20 ° to 1200 °C and next they decrease. For biggest grain size (about 44 μm) they increase up to 800 °C and next they keep constant up to 1200 °C. The micrographs analyses of fracture surfaces indicated that transgranular mode of fracture at room temperature changes to almost intergranular at higher temperatures.

Effect of Grain Size and Meso-Texture on the Impact Toughness of Ti-Microalloyed Steel

2011 ◽  
Vol 702-703 ◽  
pp. 766-769 ◽  
Author(s):  
A. Ray ◽  
Debalay Chakrabarti
Keyword(s):  
Particle Size ◽  
Grain Size ◽  
Impact Toughness ◽  
Microalloyed Steel ◽  
Charpy Impact ◽  
Impact Testing ◽  
Grain Sizes ◽  
Matrix Strength ◽  
Charpy Impact Testing ◽  
The Impact

Charpy impact testing (over the transition temperature rage) on different samples of a Ti-microalloyed steel, having the same average-TiN particle size but different average-ferrite grain sizes, showed that in spite of the presence of large TiN cuboides, ferrite grain refinement can significantly improve the impact toughness, provided the meso-texture (i.e. the intensity of low-angle boundaries) and matrix strength can be restricted to low values.

Impact Toughness of Titanium Alloys with Different Strengthening Methods

2007 ◽  
Vol 353-358 ◽  
pp. 433-437 ◽  
Author(s):  
Qiao Yan Sun ◽  
Lin Xiao ◽  
Jun Sun
Keyword(s):  
Low Temperature ◽  
Impact Toughness ◽  
Room Temperature ◽  
Alloying Elements ◽  
Initiation Energy ◽  
Impact Machine ◽  
Impact Tests ◽  
General Yielding ◽  
The Impact ◽  
Effect Of Alloying

In present paper effect of alloying elements and strengthening particle on the impact toughness were investigated. Load and energy in the impact tests were also discussed in detail for Ti-2Al, Ti-2Sn,Ti-2Zr, Ti-1Mo and Ti/TiC. Impact tests were carried out at room temperature (293K) and low temperature (83K) using a 300J capacity impact machine. Ti-1Mo, Ti-2Zr,Ti-2Sn alloys exhibit high impact toughness even at low temperature, while Ti-2Al and Ti/TiC only have high toughness at room temperature. At room temperature, general yielding occurred in all the materials, but it occurred only in Ti-1Mo, Ti-2Zr and Ti-2Sn at low temperature. It seemed that strengthening titanium couldn’t affect the elastic energy (Ei) effectively, but bring about more changes to Ep (propagation energy of crack) than to Ei (initiation energy of crack). As for the effect of alloying elements on the impact toughness, it seems to be related to the comprehensive result of the concentration and electronegative property of alloying elements. The interface between the TiC particles and matrix resulted in low toughness, especially at cryogenic temperature.

scholarly journals The Effects of Various Conditions of Short-Term Rejuvenation Heat Treatment on Room-Temperature Mechanical Properties of Thermally Aged P92 Boiler Steel

Materials ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6076
Author(s):  
Ladislav Falat ◽  
Lucia Čiripová ◽  
Viera Homolová ◽  
Miroslav Džupon ◽  
Róbert Džunda ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Impact Toughness ◽  
Room Temperature ◽  
Laves Phase ◽  
Short Term ◽  
Boiler Steel ◽  
P92 Steel ◽  
The Impact

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.

Effect of Hot Isostatic Pressing on Microstructures and Mechanical Properties of IN738LC Superalloy

2017 ◽  
Vol 898 ◽  
pp. 401-406
Author(s):  
Qun Gong He ◽  
Jun Liu ◽  
Lin Xu Li ◽  
Zhen Huan Gao ◽  
Xiao Yan Shi ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Impact Toughness ◽  
Rupture Life ◽  
Hot Isostatic Pressing ◽  
Stress Rupture ◽  
Stress Rupture Life ◽  
Isostatic Pressing ◽  
Microstructures And Mechanical Properties ◽  
The Impact

The microstructures and mechanical properties of IN738LC superalloy made by investment castings followed by Hot Isostatic Pressing (HIP) treatment have been investigated. The results revealed that after HIP treatment, the microporosities have been almost removed and the density rose by 0.21%. The eutectic size became smaller and the fraction decreased. The γ' phase was more regular and also increased in size, while a large number of secondary γ' phase appeared. With HIP treatment, the impact toughness increased from 5.0J ~ 7.0J to 8J ~ 9J and tensile strength at 200°C ~ 800°C was improved by approximately 3.2%~19.7%. In addition, the ductility and the stress rupture life have also been greatly improved as well.

Improvement on Impact Toughness of Cold Formed S420 Steel by Direct Quenching

2021 ◽  
Vol 1016 ◽  
pp. 648-653
Author(s):  
Antti Kaijalainen ◽  
Juho Mourujärvi ◽  
Juha Tulonen ◽  
Petteri Steen ◽  
Jukka I. Kömi
Keyword(s):  
Grain Size ◽  
Tensile Strength ◽  
Impact Toughness ◽  
Yield Strength ◽  
Uniform Elongation ◽  
Cold Deformation ◽  
Strength Level ◽  
Cold Forming ◽  
Direct Quenching ◽  
The Impact

The aim of this work is to study the effect cold forming rate (CFR) on the mechanical properties and microstructure of a conventional TMCP and a direct-quenched steel in 420 MPa strength level. The microstructure was characterized using FESEM-EBSD. Tensile properties and Charpy-V impact toughness were determined. As the CFR increased, the yield and tensile strength raised quite linearly with both steels. Yield strength values increased from 450 MPa (as-rolled material) to 700 MPa (25 % CFR). However, tensile strength increased less compared to yield strength. Uniform elongation decreased linearly till about 10 % CFR and total elongation till about 15 – 20 % CFR. The impact values decreased quite linearly in -40 °C and -60 °C test temperature when the cold forming rate increased. In longitudinal direction (L-T) the impact values were at high level at -40 °C and -60 °C with both steels with all CFR. In transverse direction (T-L) the impact results were lower. Impact energies were enhanced by direct quenching compared to conventional steel in every CFR stage. EBSD results showed no major difference between steels in the grain sizes in generally. However, cold forming decreased the grain size and increased low-angle grain boundaries in correlation with increasing CFR. Small size of the coarsest grains (d90%) usually indicate better toughness, however in this case the impact values were decreased even with smaller grain size as cold deformation occurs. On the other hand, the strength level increased with forming rate. Therefore, a brief discussion of the microstructural features controlling the impact toughness is given.

Impact Performance of ZnAl27Cu2.5MgMn Alloy from Room Temperature to 250°C

2014 ◽  
Vol 915-916 ◽  
pp. 597-601
Author(s):  
Ming Long Kang ◽  
Wu Hu ◽  
Jian Min Zeng
Keyword(s):  
Impact Toughness ◽  
Impact Energy ◽  
Room Temperature ◽  
Impact Testing ◽  
Impact Behavior ◽  
Impact Performance ◽  
Temperature Impact ◽  
Spectrum Curve ◽  
The Impact ◽  
Pendulum Impact

The impact performance of ZnAl27Cu2.5MgMn alloy from room Temperature to 2500 °C has been investigated by pendulum impact testing. The surface morphology of impact fracture is observed by scan electron microscope (SEM). The results indicate that impact energy of the alloy decreases as the temperature increases when the temperatures are lower than 100°C. Between 100°C and 200°C, impact energy increases as the temperature increases. And when the temperature exceeds 250°C, impact energy decreases dramatically. Impact energy gets to the maximum at room temperature. Impact behavior of the alloy can be evaluated by the width of impact spectrum curve. The wider the peak of impact spectrum curve, the higher the impact toughness. Whereas impact toughness is worse if peak is narrow.

Microstructure–Property Relationship in 22mm Thick X80 Coil Skelp

2010 ◽  
Author(s):  
M. Liebeherr ◽  
N. Bernier ◽  
D. Le`bre ◽  
N. Ilic´ ◽  
D. Quidort
Keyword(s):  
Grain Size ◽  
Impact Toughness ◽  
Electron Backscatter Diffraction ◽  
Bainitic Ferrite ◽  
Hot Strip Mill ◽  
Low Carbon ◽  
Welded Pipe ◽  
Hot Rolled ◽  
Backscatter Diffraction ◽  
The Impact

The progress in the development of heavy gauge X80 linepipe steel on coil at ArcelorMittal was recently rewarded with a 6000 ton commercial order for the production of 21.6mm wall thickness spiral welded pipe. The further product development is concentrating on the improvement of the impact toughness at low temperatures. Research is currently focussing on the relationship between the mechanical properties and the microstructure of the steels. In the present study, two industrially hot rolled X80 steels with thickness 21.6mm were investigated. The steels had the same chemical composition but were processed with different parameter sets in the hot strip mill. The two resulting low-carbon bainitic microstructures were composed predominantly of quasi-polygonal ferrite and globular bainitic ferrite / bainitic ferrite, respectively. Emphasis of the microstructure and property characterisation was laid on through-thickness gradients of grain size, hardness, texture, impact toughness and tensile properties. Accordingly, the materials were characterised at different positions in the thickness. Grain size and texture were determined by means of Electron Backscatter Diffraction (EBSD). Sub-size Charpy as well as sub-thickness tensile test specimens were taken at different positions in the cross section. The results show that the link between microstructure and properties is not at all obvious. The influence of mean grain size, grain size distribution and texture is discussed in detail.

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