Sulfur Effects on High-Temperature Creep and Fracture Behavior of 25Cr35Ni–Nb Alloys

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
Tao Chen ◽  
Xuedong Chen ◽  
Juan Ye
Keyword(s):  
Elevated Temperature ◽  
Grain Boundaries ◽  
Fracture Behavior ◽  
Elevated Temperatures ◽  
Rupture Life ◽  
Local Stress ◽  
Tensile Tests ◽  
Creep Rupture ◽  
Scanning Electron Micrographs ◽  
Nucleation Sites

Centrifugal cast 25Cr35Ni–Nb alloy furnace tubes with different contents of S are selected to investigate effects of S addition on creep and fracture behavior. Rupture tests in air at 1100 °C and 17 MPa and slow rate tensile tests at 850 °C showed that the presence of S decreased the creep rupture life and elevated temperature ductility of 25Cr35Ni–Nb alloy obviously. Scanning electron micrographs (SEM) of the fracture and energy dispersive X-ray spectroscopy (EDS) analysis results indicated that S was the important element to control creep rupture life and elevated temperature ductility. S segregated to grain boundaries at elevated temperatures, and blocky fine sulfide particles with smooth surface distribute on the grain boundaries. The presence of sulfides became effective nucleation sites for intergranular creep cavities. Micro cracks occurred by linking up cavities at elevated temperatures due to local stress concentration. Eventually, early failure happened.

Sulfur Effects on High-Temperature Creep and Fracture Behavior of 25Cr35Ni-Nb Alloys

2013 ◽  
Author(s):  
Tao Chen ◽  
Xuedong Chen ◽  
Juan Ye ◽  
Xiyun Hao
Keyword(s):  
Elevated Temperature ◽  
Grain Boundaries ◽  
Fracture Behavior ◽  
Elevated Temperatures ◽  
Rupture Life ◽  
Local Stress ◽  
Tensile Tests ◽  
Creep Rupture ◽  
Scanning Electron Micrographs ◽  
Nucleation Sites

Centrifugal cast 25Cr35Ni-Nb alloy furnace tubes with different contents of S are selected to investigate effects of S addition on creep and fracture behavior. Rupture tests in air at 1100 °C and 17 MPa and slow rate tensile tests at 850 °C showed that the presence of S decreased the creep rupture life and elevated temperature ductility of 25Cr35Ni-Nb alloy obviously. Scanning electron micrographs (SEM) of the fracture and energy dispersive X-ray spectroscopy (EDS) analysis results indicated that S was the important element to control creep rupture life and elevated temperature ductility. S segregated to grain boundaries at elevated temperatures, blocky fine sulfide particles with smooth surface distribute on the grain boundaries. The presence of sulfides became effective nucleation sites for intergranular creep cavities. Micro cracks occurred by linking up cavities at elevated temperatures due to local stress concentration. Eventually, early failure happened.

Experimental Investigation of Ti-6Al-4V with a Biaxial Tensile Test Setup at Elevated Temperature

2014 ◽  
Vol 622-623 ◽  
pp. 273-278 ◽  
Author(s):  
Marion Merklein ◽  
Sebastian Suttner ◽  
Adam Schaub
Keyword(s):  
Elevated Temperature ◽  
Elevated Temperatures ◽  
Tensile Tests ◽  
Advanced Materials ◽  
Uniaxial Tensile ◽  
Plastic Yielding ◽  
Characterization Methods ◽  
Specific Strength ◽  
Biaxial Tensile ◽  
Stress States

The requirement for products to reduce weight while maintaining strength is a major challenge to the development of new advanced materials. Especially in the field of human medicine or aviation and aeronautics new materials are needed to satisfy increasing demands. Therefore the titanium alloy Ti-6Al-4V with its high specific strength and an outstanding corrosion resistance is used for high and reliable performance in sheet metal forming processes as well as in medical applications. Due to a meaningful and accurate numerical process design and to improve the prediction accuracy of the numerical model, advanced material characterization methods are required. To expand the formability and to skillfully use the advantage of Ti-6Al-4V, forming processes are performed at elevated temperatures. Thus the investigation of plastic yielding at different stress states and at an elevated temperature of 400°C is presented in this paper. For this reason biaxial tensile tests with a cruciform shaped specimen are realized at 400°C in addition to uniaxial tensile tests. Moreover the beginning of plastic yielding is analyzed in the first quadrant of the stress space with regard to complex material modeling.

scholarly journals CREEP RUPTURE LIFE OF PRE-STRAINED SUPERALLOY N07080

2021 ◽  
Vol 9 (10) ◽  
pp. 1167-1176
Author(s):  
Omer Beganovic ◽  
Keyword(s):  
Stress Concentration ◽  
Grain Boundaries ◽  
Rupture Life ◽  
Warm Rolling ◽  
Creep Rupture ◽  
Cavity Nucleation ◽  
Standard Heat ◽  
Creep Cavity ◽  
Heat Treated

The creep of the pre-strained superalloy N07080 is described in this work. The pre-strain was achieved by warm rolling at 1050 oC.-The warm rolling was performed due to additional strengthening, i.e increasing of the superalloy hardness.-The pre-strain drastically reduces the creep rupture life of the superalloy compared to the creep rupture life of the standard heat treated superalloy.-The drastic reductionof the creep rupture life is result of rapid creep cavity nucleation on stress concentration sites along primary grain boundaries of the pre-strained superalloy.-Recrystallization eliminates potential sites for rapid cavity nucleation and prolongates the creep rupture life.

Fatigue responses of cracked Ti/APC-2 nanocomposite laminates at elevated temperature

2019 ◽  
Vol 54 (13) ◽  
pp. 1705-1715
Author(s):  
MHR Jen ◽  
GT Kuo ◽  
YH Wu ◽  
YJ Chen
Keyword(s):  
Mechanical Properties ◽  
Elevated Temperature ◽  
Composite Laminates ◽  
Elevated Temperatures ◽  
Tensile Tests ◽  
Cyclic Tests ◽  
Constant Length ◽  
Nano Powder ◽  
Strength And Stiffness ◽  
Inclined Angle

The mechanical properties and fatigue responses of Ti/APC-2 neat and nanocomposites with inclined single-edged cracks due to tensile and cyclic tests at elevated temperature were investigated. Two types of composite laminates [Ti/(0/90)s/Ti] were fabricated with and without (W/WO) nanoparticles SiO2 of optimal 1 wt.%. The geometry and dimensions of specimens were L × W × t = 240 × 25 × 1.55 mm3. The cracks were of constant length 3 mm and width 0.3 mm. The inclined angles were 0°, 45°, and 60°. Both the tensile and cyclic tests were conducted at elevated temperatures 25℃ (RT), 100℃, 125℃, and 150℃. From the tensile tests we obtained the load vs. displacement curves for both types of laminates with varied inclinations at elevated temperatures. Next, we received the applied load vs. cycles curves for the same laminates with inclined cracks at the corresponding temperature due to cyclic tests. According to the experimental data of both tensile and cyclic tests the mechanical properties, such as strength, stiffness, and life, decreased as the temperature rises. The greater the inclined angles were, the greater the strength and stiffness were. Similarly, the fatigue life was in the same trend. However, the effect of inclined angle on mechanical properties was more strong than those of temperature. The mechanical properties of nanocomposite laminates were higher than those of neat composite laminates, but not significant. The main reason was that the enhancement of spreading nano-powder silica on the laminate interfaces did not effectively eliminate the stress intensity at the crack tip locally.

Experimental Study on the Mechanical Property and Forming Limit of Magnesium Sheet at Elevated Temperatures

2009 ◽  
Author(s):  
Y. Huang ◽  
J. Huang ◽  
J. Cao
Keyword(s):  
Elevated Temperature ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Tensile Tests ◽  
Alloy Sheet ◽  
Dome Height ◽  
Forming Limit ◽  
Uniaxial Tensile ◽  
Magnesium Sheet

Magnesium alloy sheet has received increasing attention in automotive and aerospace industries. It is widely recognized that magnesium sheet has a poor formability at room temperature. While at elevated temperature, its formability can be dramatically improved. Most of work in the field has been working with the magnesium sheet after annealed around 350°C. In this paper, the as-received commercial magnesium sheet (AZ31B-H24) with thickness of 2mm has been experimentally studied without any special heat treatment. Uniaxial tensile tests at room temperature and elevated temperature were first conducted to have a better understanding of the material properties of magnesium sheet (AZ31B-H24). Then, limit dome height (LDH) tests were conducted to capture forming limits of magnesium sheet (AZ31B-H24) at elevated temperatures. An optical method has been introduced to obtain the stress-strain curve at elevated temperatures. Experimental results of the LDH tests were presented.

scholarly journals Microstructural Evolution and Short-Term Creep Rupture of the Simulated HAZ in T92 Steel Normalized at Different Temperatures

Metals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1310 ◽  
Author(s):  
Tai-Jung Wu ◽  
Chien-Chun Liao ◽  
Tai-Cheng Chen ◽  
Ren-Kae Shiue ◽  
Leu-Wen Tsay
Keyword(s):  
Grain Boundaries ◽  
Elevated Temperatures ◽  
Creep Rupture ◽  
Infrared Heating ◽  
Short Term ◽  
Creep Tests ◽  
Steel Tubes ◽  
Austenite Grain ◽  
Term Creep ◽  
Short Term Creep

T92 steel tubes have been widely applied in advanced supercritical boilers to replace Gr.91 tubes. Simulated samples with microstructures similar to those present in the heat-affected zone (HAZ) of a T92 steel weld were subjected to short-term creep tests in the study. T92 steel tubes were normalized at either 1213 K (L) or 1333 K (H) for 1 h, followed by tempering (T) at 1033 K for 2 h. After the normalizing and tempering treatments, the HT samples comprised finer precipitates but in greater numbers along the prior austenite grain boundaries (PAGBs) and martensite lath boundaries, as compared with those of the LT samples. The HAZ microstructures in the T92 steel welds were simulated by using an infrared heating system, which included over-tempering (OT, below AC1) and partial transformation (PT, slightly below AC3) zones. Martensite laths in the OT sample were more likely to be replaced by numerous cellular structures or subgrains together with spherodized carbides mainly located at the lath and austenite grain boundaries. Furthermore, coarser but fewer carbides were found along the refined lath and grain boundaries in the PT samples, in comparison with other samples in each group. Short-term creep tests showed that the PT samples were more likely to fracture than other samples in each group. Moreover, under the same testing conditions, the microstructures of T92 steel were more stable and resistant to degradation than those of T91 steel after welding or loading at elevated temperatures. Such events were responsible for higher creep resistance of the simulated T92 samples than that of the simulated T91 samples under the same creep-rupture conditions.

Creep Rupture Properties of High-Temperature Bainitic Steels After Weld Repair

2000 ◽  
Vol 122 (3) ◽  
pp. 259-263 ◽  
Author(s):  
J. E. Indacochea ◽  
G. Wang ◽  
R. Seshadri ◽  
Y. K. Oh
Keyword(s):  
High Temperature ◽  
Heat Affected Zone ◽  
Elevated Temperatures ◽  
Rupture Life ◽  
Creep Rupture ◽  
Welding Parameters ◽  
Structure Stability ◽  
Rotor Steel ◽  
Bainitic Steels ◽  
Alloy Steels

Welded high-temperature power plant components can experience a greater risk of failure by creep during service, when compared to similar as-wrought components. The heat-affected zone (HAZ) of alloy steels is usually the region of a weldment exhibiting poor mechanical properties. The arc welding of an ASTM A470, Class 8-rotor steel in this study identified the intercritical heat affected zone (ICHAZ) as the weakest region in terms of creep rupture life. The type of welding procedure significantly affects this region, but most important are the welding parameters utilized. Because of the microstructural heterogeneity of the HAZ and sensitivity of these microstructures to changes when exposed to elevated temperatures, their performance at later times is difficult to predict. Extrapolation techniques are limited in value for predicting service lives of homogeneous materials, because these do not incorporate the microstructure changes of the materials during high temperature operation. They are even less useful for predicting the operating lives of weldments. This paper considers the creep performance and structure stability of the ICHAZ of 12 percent Cr and 214-1Mo vanadium modified weldments produced on a retired CrMoV rotor steel. [S0094-4289(00)00303-0]

Characteristics of Material Degradation for Thermal Aged X20CrMoV12 1 Steel

2004 ◽  
Vol 449-452 ◽  
pp. 537-540 ◽  
Author(s):  
Y.K. Chung ◽  
Jong Jin Park ◽  
Cheol Hong Joo ◽  
Ik Min Park
Keyword(s):  
Creep Strength ◽  
Rupture Life ◽  
Regression Line ◽  
Tensile Tests ◽  
Creep Rupture ◽  
Material Degradation ◽  
Austenite Grain ◽  
Aging Parameter ◽  
Prior Austenite Grain

X20CrMoV12 1 steels were exposed at three different high temperatures and various durations. Aging parameter, LMP s, was used to describe long-term thermal history. Creep rupture, hardness and tensile tests for aged X20CrMoV12 1 steels were carried out. Yield strength was slightly decreased and hardness was rapidly decreased afterLMP s reached 20.6. Creep strength of aged X20CrMoV12 1 steel decreased rapidly after the LMPs reached 20.6. It was shown that the creep strength decreased due to the coarsening of acicular type M23C6 at subgrain boundaries and the agglomeration of M23C6 at prior austenite grain boundaries. After LMPs reached 20.6, the assumed linear regression line of stress and Larson-Miller parameter,LMPf, also moved toward a lower LMPf region as aging parameter increased. The dependency of creep rupture life on the microstructural degradation could be represented by CLMPs, which is LMPf at stress of 1 kg/mm2. It was found that the creep rupture life of X20CrMoV12 1 steel could be predicted by considering the material degradation during and prior to creep test.

Optimization of Dissimilar Friction Welding and Creep Rupture Tests for Nuclear Reactor Component Materials

2006 ◽  
Vol 306-308 ◽  
pp. 1019-1024 ◽  
Author(s):  
Yu Sik Kong ◽  
Sang Woo Kwon ◽  
Seon Jin Kim
Keyword(s):  
Stainless Steel ◽  
Friction Welding ◽  
Copper Alloy ◽  
Elevated Temperatures ◽  
Tensile Tests ◽  
Heating Time ◽  
Creep Rupture ◽  
Welding Parameters ◽  
Parameter Method ◽  
Steel Bars

An experimental work of dissimilar friction welding was conducted using 15 mm diameter solid bar in copper alloy (Cu-1Cr-0.5Zr) to stainless steel (STS316L) for being used as fusion reactor component materials, not only to optimize the friction welding parameters, but also to investigate the elevated temperature tensile strength and creep rupture properties for the friction welded joints under the optimal welding conditions. The main friction welding parameters were selected to endure good quality welds on the basis of visual examination, tensile tests, Vickers hardness survey of the bond area and HAZ. For friction weld joining of copper alloy to stainless steel bars, the total upset increases lineally as increasing heating time. Optimal welding conditions were selected as follows: Rotational speed 2000rpm, friction pressure 80MPa, upsetting pressure 140MPa, heating time 2 second, upsetting time 5 second and total upset 13mm. The weld interface of dissimilar friction welded steel bars was mixed strongly. And also the creep properties and creep life prediction by Larson-Miller parameter method were presented at the elevated temperatures of 300, 400 and 500oC.

Effect of Preoxidation and Grain Size on Ductility of a Boron-Doped Ni3Al at Elevated Temperatures

1988 ◽  
Vol 133 ◽  
Author(s):  
M. Takeyama ◽  
C. T. Liu
Keyword(s):  
Grain Boundaries ◽  
Elevated Temperatures ◽  
Short Circuit ◽  
Tensile Tests ◽  
Oxide Formation ◽  
Fine Grained ◽  
Oxygen Penetration ◽  
Grain Sizes ◽  
Boron Doped ◽  
The Difference

ABSTRACTThe ductility of preoxidized Ni3Al (Ni-23Al-0.5Hf-0.2B, at.%) specimens with various grain sizes (17∼193 μm) was evaluated by means of tensile tests at 600 and 760°C in vacuum. It was found that the preoxidation does not affect the ductility of the finest-grained material at either temperature, whereas it causes severe embrittlement in the largest-grained material, especially at 760°C. A continuous, thin Al-rich oxide layer, which forms on the fine-grained samples, protects the underlying alloy from oxygen penetration, preventing any loss of ductility, whereas the nickel-rich oxide which forms on the large-grained samples allows oxygen to penetrate along grain boundaries, causing severe embrittlement. The grain boundaries act as short-circuit paths for rapid diffusion of aluminum atoms from the bulk to the surfaces, and this is responsible for the difference in oxidation behavior between fine- and large-grained materials. The embrittlement of large-grained samples can be eliminated through control of oxide formation on Ni3Al surfaces.

Sign in / Sign up

Export Citation Format

Share Document