Effect of Radical Nitriding on Fatigue Strength of Ni-Base Superalloy

2009 ◽  
Vol 417-418 ◽  
pp. 205-208 ◽  
Author(s):  
Kazuhiro Morino ◽  
Norio Kawagoishi ◽  
K. Yamane ◽  
K. Fukada
Keyword(s):  
Fatigue Strength ◽  
Base Alloy ◽  
Compound Layer ◽  
Fatigue Tests ◽  
Bending Fatigue ◽  
Propagation Behavior ◽  
Initiation And Propagation ◽  
Rotating Bending Fatigue ◽  
Rotating Bending ◽  
Base Superalloy

In order to investigate the effect of nitriding on the crack initiation and propagation behavior of Ni-base super alloy, Alloy 718, rotating bending fatigue tests were carried out until 108 cycles at room temperature. By nitriding at 500°C for 12h, compound layer of about 5μm in thickness was formed and the initiation of a fatigue crack was strongly suppressed causing the increase in fatigue strength. A crack initiated in brittle manner at the compound layer in all of fractures. However the crack propagated in ductile manner controlled by the property of the base alloy. That is, there is no or little influence of nitriding on the crack growth rate of the alloy.

Effects of Microstructure and Humidity on Fatigue Strength of Maraging Steel

2008 ◽  
Vol 385-387 ◽  
pp. 113-116
Author(s):  
M. Miyazono ◽  
Norio Kawagoishi ◽  
Qing Yuan Wang ◽  
Eiji Kondo ◽  
Takanori Nagano
Keyword(s):  
Grain Size ◽  
Fatigue Strength ◽  
Fatigue Tests ◽  
Specimen Surface ◽  
Bending Fatigue ◽  
Maraging Steels ◽  
Initiation And Propagation ◽  
Rotating Bending Fatigue ◽  
Rotating Bending ◽  
Different Grain Size

Rotating bending fatigue tests were carried out for maraging steels with different grain size in moist air in order to investigate the effects of humidity, grain size and reversion austenite on fatigue strength of the steel. Fatigue strength was decreased by humidity, and the decrease in fatigue strength was large in larger grain sized steel. Both of the initiation and propagation of a crack were promoted by humidity. Many cracks initiated at the specimen surface and intergranular cracks were observed at specimen surface and on fracture surface when humidity was high. The decrease in fatigue strength by humidity was suppressed by formation of reversion austenite.

Ultrasonic Fatigue of Radical Nitrided Ni-Base Superalloy

2009 ◽  
Vol 417-418 ◽  
pp. 209-212
Author(s):  
K. Yamane ◽  
Norio Kawagoishi ◽  
Kazuhiro Morino ◽  
K. Fukada
Keyword(s):  
Fatigue Strength ◽  
Fracture Surface ◽  
Fatigue Tests ◽  
Loading Frequency ◽  
Bending Fatigue ◽  
Fatigue Process ◽  
Rotating Bending Fatigue ◽  
Ultrasonic Fatigue ◽  
Rotating Bending ◽  
Base Superalloy

Ultrasonic and rotating bending fatigue tests were carried out for aged and nitrided Ni-base super alloys to investigate the effects of loading frequency and nitriding on fatigue strength. Loading frequencies were 19.5 kHz under ultrasonic and 50 Hz under rotating bending, respectively. Fatigue strength under ultrasonic was higher than that under rotating bending in both alloys. Moreover, in both tests, fatigue strength was improved by nitriding. The increase in fatigue strength by nitriding was large in ultrasonic fatigue. These results were discussed through the successive observation of fatigue process at specimen surface and fracture surface observation.

Characterization of Crack Growth Behavior of Carburized SCM415 Steel under Cyclic Rotating Bending

2019 ◽  
Vol 298 ◽  
pp. 13-18
Author(s):  
Takahiro Matsueda ◽  
Kei Ushizima ◽  
Koshiro Mizobe ◽  
Katsuyuki Kida
Keyword(s):  
Stress Amplitude ◽  
Fatigue Tests ◽  
Crack Growth Behavior ◽  
Fracture Origin ◽  
Propagation Behavior ◽  
Carburized Steel ◽  
Steel Bar ◽  
Initiation And Propagation ◽  
Rotating Bending Fatigue ◽  
Rotating Bending

Carburized steel was used in severe and cyclic loading conditions such as bearing and structural components. In this study rotating bending fatigue tests were carried out to observe the crack initiation and propagation behavior of carburized JIS SCM415 steel bar whose diameter was 10.0 mm. Transition area origin (TRO) crack on fracture surfaces were observed with scanning electron microscope. The depth of fracture origins was about 0.9 mm. TRO crack was observed around the fracture origin which was nucleated at the edge of carburized layer, and the crack propagated toward the surface and the inside core. Stress amplitude was modified with depth of crack origin, and S-N curve was corrected with modified applied stress amplitude σM. In order to reveal the crack propagation behavior around the boundary between the hardened and the soft core area, stress intensity factor (SIF) on crack front was also computed.

INITIATION AND PROPAGATION BEHAVIOR OF A FATIGUE CRACK OF ALLOY 718

2010 ◽  
Vol 24 (15n16) ◽  
pp. 2857-2862 ◽  
Author(s):  
NORIO KAWAGOISHI ◽  
MASAHIRO GOTO ◽  
XISHU WANG ◽  
QINGYUAN WANG
Keyword(s):  
Fatigue Strength ◽  
Fatigue Tests ◽  
Alloy 718 ◽  
Aged Material ◽  
Propagation Behavior ◽  
Peak Aged Condition ◽  
Initiation And Propagation ◽  
High Fatigue ◽  
Rotating Bending Fatigue ◽  
Peak Aged

Rotating bending fatigue tests were carried out at room temperature and 500°C for alloy 718 with nearly the same static strength but different precipitated particles, i.e. a peak aged condition (720°C-10h) and a double aged one (720°C-8h, 620°C-8h), in order to investigate the effect of precipitated particles on crack initiation and propagation behavior. Fatigue strength was higher in the double aged material than in the peak one at both temperatures. The main reason for high fatigue strength of the double aged material was that the propagation of a small crack with a few grain sizes was suppressed by the carbide particles precipitated in a grain.

Sub-Surface Fatigue Strength of a Steel

1969 ◽  
Vol 11 (4) ◽  
pp. 432-443 ◽  
Author(s):  
P. F. Bray
Keyword(s):  
Fatigue Strength ◽  
Residual Stresses ◽  
Fatigue Limit ◽  
Fatigue Tests ◽  
Bending Fatigue ◽  
Surface Fatigue ◽  
Test Pieces ◽  
Surface Failure ◽  
Rotating Bending Fatigue ◽  
Rotating Bending

Rotating bending fatigue tests on En 40B steel gave a fatigue limit for surface failure of 30·5 tonf/in2. With nitrided test-pieces sub-surface failures were produced and, with no allowance being made for residual stresses, a fatigue limit of 34·5 tonf/in2 was obtained for sub-surface failure. In the absence of residual stresses this fatigue limit would probably have been higher.

Effect of Humidity on Fatigue Strength of Age-Hardened Al Alloy

2009 ◽  
Vol 417-418 ◽  
pp. 373-376
Author(s):  
T. Fukudome ◽  
Norio Kawagoishi ◽  
K. Kariya
Keyword(s):  
Fatigue Strength ◽  
Fracture Mechanism ◽  
Fatigue Tests ◽  
Shear Mode ◽  
Al Alloy ◽  
Bending Fatigue ◽  
Rotating Bending Fatigue ◽  
Ultrasonic Fatigue ◽  
Rotating Bending ◽  
The Difference

Ultrasonic and rotating bending fatigue tests were carried out using plain specimens and specimens with a small blind hole for an extruded and age-hardened Al alloy 7075-T6 in different environments in order to investigate the effect of humidity on fatigue strength and fracture mechanism. Fatigue strength was decreased by high humidity under both tests. The effect of humidity on fatigue strength was larger in ultrasonic fatigue. The humidity affected both of crack initiation and propagation processes. Crack propagated in tensile mode then changed to shear mode macroscopically in all environments under ultrasonic fatigue, though it was only in tensile mode under rotating bending fatigue. These differences in fracture mechanism related to the difference in environmental effect on fatigue strength in both tests.

Effect of Humidity on Fatigue Strength of Age-Hardened Al Alloy under Rotating Bending

2010 ◽  
Vol 452-453 ◽  
pp. 745-748 ◽  
Author(s):  
Norio Kawagoishi ◽  
K. Kariya ◽  
Yan Nu ◽  
S. Furumoto ◽  
Eiji Kondo
Keyword(s):  
Fatigue Strength ◽  
Fatigue Tests ◽  
Propagation Mode ◽  
Shear Mode ◽  
Al Alloy ◽  
High Humidity ◽  
Mode Propagation ◽  
Initiation And Propagation ◽  
Rotating Bending Fatigue ◽  
Rotating Bending

In order to investigate the effect of humidity on fatigue strength of an extruded and age-hardened Al alloy 7075-T6, rotating bending fatigue tests were carried out using plain specimens in environments of controlled relative humidity of 25%, 50%, 75% and 85% and distilled water. The cross section of the alloy has a marked texture of (111) plane. Although fatigue strength was decreased by high humidity, the decrease by high humidity was very small when the humidity was lower than about 60% -70% and fatigue strength was largely decreased over the humidity. Both of initiation and propagation of a crack were accelerated by high humidity. In high humidity, a crack propagated in a shear mode macroscopically and it was ductile in company with many glide planes and voids microscopically. That is, the propagation was not a tensile mode with brittle facets even in water. The shear mode propagation inclined about 35° to the extruded direction and fracture surface was (100) plane, meaning that the shear mode propagation of a crack was mainly caused by the marked texture of the alloy. The propagation mode of a crack was affected by not only environment but also stress level.

Improvement of Fatigue Strength of Maraging Steel by Shot Peening

2007 ◽  
Vol 348-349 ◽  
pp. 537-540
Author(s):  
Norio Kawagoishi ◽  
Takanori Nagano ◽  
M. Moriyama ◽  
Eiji Kondo
Keyword(s):  
Fatigue Strength ◽  
Maraging Steel ◽  
Shot Peening ◽  
Fine Particles ◽  
Fatigue Tests ◽  
Fracture Origin ◽  
Bending Fatigue ◽  
Rotating Bending Fatigue ◽  
Rotating Bending ◽  
Points Of View

Rotating bending fatigue tests up to 108 cycles were carried out to investigate the effects of shot peening on the fatigue strength and the fracture mechanism in an 18 % Ni maraging steel by using shot particles of various sizes or hardness. Fatigue strength was increased markedly by shot peening in the wide region of fatigue life. The S-N curves showed duplex S-N properties because of the transition of fracture origin from the specimen surface in the short life region to the subsurface in the long life one. Double shot peening by using super-hard fine particles was effective to improve the fatigue strength for surface fracture, though the fatigue strength for an internal fracture was hardly influenced. These results were discussed from the points of view of effects of surface roughness, residual stress and work hardening on the fatigue strength.

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