A Study of Nitrogen Effect on the Characteristics of Creep-Rupture in 18Cr-9Ni Austenitic Steels

2005 ◽  
pp. 409-414
Author(s):  
Jae Kyoung Shin ◽  
Soo Woo Nam ◽  
Soo Chan Lee
Keyword(s):  
Creep Rupture ◽  
Austenitic Steels ◽  
Nitrogen Effect

A Study of Nitrogen Effect on the Characteristics of Creep-Rupture in 18Cr-9Ni Austenitic Steels

2005 ◽  
Vol 297-300 ◽  
pp. 409-414 ◽  
Author(s):  
Jae Kyoung Shin ◽  
Soo Woo Nam ◽  
Soo Chan Lee
Keyword(s):  
Grain Boundary ◽  
Stainless Steels ◽  
Rupture Life ◽  
Austenitic Stainless Steels ◽  
Creep Rupture ◽  
Austenitic Steels ◽  
Nitrogen Effect ◽  
Transmission Electron ◽  
The Difference ◽  
Nitrogen Contents

To understand the effects of nitrogen on high temperature, creep-rupture tests have been conducted at 973 and 1073K for 18Cr-9Ni austenitic stainless steels with 0.14 and 0.08wt% nitrogen contents. It is observed that creep-rupture life of 18Cr-9Ni-0.14N steel is longer than that of 18Cr-9Ni-0.08N steel. To verify the difference in creep-rupture life between two alloys, scanning electron microscope and transmission electron microscopy are used to observe the microstructure. From the observations, it is known that the Cr-rich carbides are precipitated mainly at the grain boundary. Comparing the ratio of the linear density of the precipitate particles, the higher nitrogen content is, the less carbide is precipitated. Nitrogen might retard the formation of carbides at the grain boundary and reduce the density of cavity sites which are one of the main grain boundary damages.

scholarly journals Effects of Carbon, Nitrogen, and Phosphorus on Creep Rupture Ductility of High Purity Ni-Cr Austenitic Steels

1989 ◽  
Vol 75 (5) ◽  
pp. 825-832
Author(s):  
Takanori NAKAZAWA ◽  
Hideo ABO ◽  
Mitsuru TANINO ◽  
Hazime KOMATSU
Keyword(s):  
High Purity ◽  
Creep Rupture ◽  
Austenitic Steels ◽  
Nitrogen And Phosphorus ◽  
Rupture Ductility

Cold Work Effect on Creep Rupture Strength of Austenitic Boiler Steels

2007 ◽  
Author(s):  
Fujimitsu Masuyama
Keyword(s):  
High Temperature ◽  
Creep Strength ◽  
Rupture Strength ◽  
Cold Work ◽  
Creep Rupture ◽  
Austenitic Steels ◽  
Chemical Compositions ◽  
Creep Rupture Strength ◽  
Cold Worked

In order to clarify the effect of cold work, warm work at working temperatures of up to 400°C and chemical compositions on the creep rupture strength of austenitic steels used for boiler tubing and high temperature support structures, long-term creep rupture tests were carried out on typical 18Cr-8Ni system steels consisting of TP304H, TP316H, TP321H and TP347H grade tubes and of TP321 plates. The long-term (100,000 hours) creep rupture strength of these steels was evaluated in terms of working ratio and Ni-equivalent. It was consequently clarified that creep rupture strength was substantially reduced in the cold-worked TP321 and TP321H materials, although warm-work resulted in less work-induced deterioration. It was also found creep rupture strength was enhanced by the higher Ni-eq in 18Cr-8Ni austenitic steels, and that the combined conditions of working ratio and Ni-eq govern the creep rupture strength criteria of weaker or stronger than as-received strength. Additionally the effect of cold work on the creep rupture strength and ductility of recently developed creep-strength enhanced 23Cr austenitic stainless steel (a candidate material for the hot end of superheaters in ultra-high temperature fossil-fired power plants) was considered. The strength of cold worked 23Cr austenitic steel was observed to fall below the as-received strength at stresses within about 120MPa, while re-solution annealing recovered the creep strength level to the as-received strength across the entire stress region.

Prediction of Creep-Rupture Properties for Austenitic Steels Undergone Neutron Irradiation

2009 ◽  
Author(s):  
B. Z. Margolin ◽  
A. G. Gulenko ◽  
A. A. Buchatsky
Keyword(s):  
Neutron Irradiation ◽  
Fracture Criterion ◽  
Void Nucleation ◽  
Rupture Strength ◽  
Creep Rupture ◽  
Austenitic Steels ◽  
Void Evolution ◽  
Fracture Of Materials ◽  
Rupture Properties ◽  
Strength And Ductility

The paper presents the physical and mechanical model that allows predicting fracture of materials subjected to neutron irradiation under creep. The model is based on the equations of void nucleation and growth on grain boundaries that were proposed earlier. The equations are developed for the case of neutron irradiation of a material. The constitutive equations describing viscoplastic deformation of a material with regard to void evolution are formulated. The criterion of microplastic collapse of a unit cell is used as a fracture criterion. The creep-rupture strength and ductility of austenitic materials in the initial and irradiated conditions with different neutron flux levels are predicted on the basis of the model. The calculated results are compared with the available experimental data.

Creep Rupture Strength Evaluation With Region Splitting by Half Yield

2013 ◽  
Author(s):  
Kazuhiro Kimura
Keyword(s):  
Creep Strength ◽  
Rupture Strength ◽  
Rupture Life ◽  
Creep Rupture ◽  
Austenitic Steels ◽  
Ferritic Steels ◽  
Creep Rupture Strength ◽  
Stress Regime ◽  
Bainitic Microstructure ◽  
Creep Resistant Steels

Creep strength of ferritic and austenitic steels has been investigated on the correlation between stress vs. creep rupture life curve and 50% of 0.2% offset yield stress (half yield) at the temperatures. Inflection of stress vs. creep rupture life curve was recognized on ferritic creep resistant steels with martensitic or bainitic microstructure. However, no identifiable correlation was observed on ferritic steels with ferrite and pearlite microstructure, as well as austenitic steels and superalloys except for several alloys. Ferritic steel with martensitic or bainitic microstructure indicates softening during creep exposure, however, hardening due to precipitation takes place in the ferritic steel with ferrite and pearlite microstructure and austenitic steels. This difference in microstructural evolution is associated with indication of inflection at half yield. Stress range of half yield in the stress vs. creep life diagram of creep strength enhanced ferritic steels is wider than that of conventional ferritic creep resistant steels with martensitic or bainitic microstructure. As a result of wide stress range of boundary condition, risk of overestimation of long-term creep rupture strength by extrapolating the data in high-stress regime to low-stress regime is considered to be high for creep strength enhanced ferritic steels.

The effect of residuals on the elevated temperature properties of some creep resistant steels

1980 ◽  
Vol 295 (1413) ◽  
pp. 279-288 ◽  
Keyword(s):  
Elevated Temperature ◽  
Rupture Life ◽  
Creep Rupture ◽  
Austenitic Steels ◽  
Individual Element ◽  
Nitrogen And Phosphorus ◽  
Rupture Ductility ◽  
Aluminium Copper ◽  
Creep Resistant Steels ◽  
Rupture Properties

The effect of residuals and other deliberate minor additions on the elevated temperature properties of austenitic, CrMo and CrMoV steels is reviewed and those that affect these properties are identified. The elements boron, molybdenum, nitrogen and phosphorus in austenitic steels all increased creep rupture life although only boron and molybdenum were beneficial to rupture ductility. In the ferritic steels the embrittling elements antimony, arsenic, phosphorus and tin were considered together with aluminium, copper, silicon, titanium and boron. It is apparent that the effect of an individual element on creep rupture properties is dependent on the other elements present. However, in a 1 %CrMoVTiB steel additions of copper plus nickel and arsenic plus tin decrease rupture life although only the latter two reduce ductility. Similarly, in a 2 1/4% Cr1% Mo steel arsenic has a detrimental effect on ductility and tin and phosphorus have been identified as segregating to prior austenite grain boundaries. In contrast, silicon in a 2 1/4%Cr1 %Mo steel can improve ductility. Aluminium can improve both the creep life and ductility of 1 %CrMoVTiB steels, as can boron in the presence of titanium.

Strengthening of an Al-Containing Austenitic Stainless Steel at High Temperature

2013 ◽  
Author(s):  
Xianping Dong ◽  
Lin Zhao ◽  
Feng Sun ◽  
Lanting Zhang
Keyword(s):  
High Temperature ◽  
Mechanical Treatment ◽  
Rupture Life ◽  
Creep Rupture ◽  
Austenitic Steels ◽  
Induction Melting ◽  
Strengthening Effect ◽  
Low Carbon ◽  
Nano Scale ◽  
Thermo Mechanical Treatment

Three Al-containing austenitic steels with slightly different contents of Nb, V and C in the Fe-19.95Ni-14.19Cr-2.25Al-2.46Mo-1.95Mn-0.15Si-0.01B (wt.%) system were designed to study the effect of precipitations on creep/rupture resistance. After induction melting, alloys were cast into a metal mold followed by thermo-mechanical treatment. A continuous Al-rich oxide scale was formed on the surface after exposure at 800°C for 146 hrs in air. By decreasing the C content from 0.07 to 0.04%, coarse NbC precipitates in the as-cast microstructure could be removed during annealing treatment. Thermo-mechanical treatment enabled nano-scale precipitation of NbC in the alloys containing 0.04% C. Although the yield strength of the alloy with 0.07% C was relatively high at 750°C, its creep/rupture life was 164 hrs at 700°C/150 MPa. Alloys having low carbon content formed a uniform fine MC precipitation around 10–20 nm and showed a creep/rupture life between 1002 and 1530 hrs at 700°C/150 MPa. This is comparable with that of super304H tested under the same condition. Fe2(Mo,Nb) Laves phase was found in the microstructure after creep/rupture testing. NiAl precipitated in alloys after creep/rupture testing for more than 1000 hrs. However, strengthening effect from these two phases is not obvious, indicating that nano-scale NbC precipitates are the major source of strengthening during creep/rupture at high temperature. In addition, nano-scale (Nb,V)C was found in V containing alloy corresponding to the longest creep/rupture life.

Tensile Creep of Y-Si3N4: II. Cavitation

1991 ◽  
Vol 49 ◽  
pp. 972-973 ◽  
Author(s):  
B. J. Hockey ◽  
S. M. Wiederhorn
Keyword(s):  
Silicon Nitride ◽  
Creep Rupture ◽  
Tensile Creep ◽  
Sintering Aids ◽  
Microstructural Changes

ATEM has been used to characterize three different silicon nitride materials after tensile creep in air at 1200 to 1400° C. In Part I, the microstructures and microstructural changes that occur during testing were described, and consistent with that description the designations and sintering aids for these materials were: W/YAS, a SiC whisker reinforced Si3N4 processed with yttria (6w/o) and alumina (1.5w/o); YAS, Si3N4 processed with yttria (6 w/o) and alumina (1.5w/o); and YS, Si3N4 processed with yttria (4.0 w/o). This paper, Part II, addresses the interfacial cavitation processes that occur in these materials and which are ultimately responsible for creep rupture.

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