scholarly journals Deformation and Fracture in Small Punch Creep Tests, and Influence Factors on Creep Rupture Life (Testing Environment and Radius of Lower Die)

2011 ◽  
Vol 77 (784) ◽  
pp. 2046-2053 ◽  
Author(s):  
Ken-ichi KOBAYASHI ◽  
Masahiro KANEKO ◽  
Hideo KOYAMA ◽  
Gavin C. STRATFORD ◽  
Masaaki TABUCHI
Keyword(s):  
Rupture Life ◽  
Influence Factors ◽  
Creep Rupture ◽  
Life Testing ◽  
Creep Tests ◽  
Small Punch ◽  
Testing Environment ◽  
Deformation And Fracture

Influence of Testing Environment on SP Creep Rupture Lives

2013 ◽  
Author(s):  
Ken-ichi Kobayashi ◽  
Sho Takei
Keyword(s):  
Oxide Scale ◽  
Residual Life ◽  
Rupture Life ◽  
High Vacuum ◽  
Creep Rupture ◽  
Test Duration ◽  
Destructive Testing ◽  
Creep Tests ◽  
Testing Environment ◽  
High Temperature Components

Small Punch (SP) Creep test has been recognized as a semi destructive testing method to examine residual life of creep in high temperature components. Employing 2.25Cr-1Mo steel (SCMV4), SP creep tests were conducted at 600°C both in air and in high vacuum to examine the influence of oxidation on the long-term rupture life of the SP creep tests. As a test result, the creep rupture life in air was shorter than that in vacuum when the rupture life was less than 1000 hours. Reduction of rupture lives in air was approximately a half of them tested in vacuum. However when the creep rupture life was longer than 1000 hours, little difference emerged even if the testing atmosphere was different. A thickness of the oxide scale formed on SP creep specimens in air increased with the test duration. The experimental test results showed that the oxide scale affected on a coefficient of friction between the loading ball and the SP creep specimen. Furthermore the oxide scale formed in air did not always peel off from the test specimen, and the thick oxide scale endured a part of applied load in the longer life test.

Influence of Testing Environment and Radius of Die Shoulder on SP Creep Rupture Life

2011 ◽  
Author(s):  
Ken-ichi Kobayashi ◽  
Masahiro Kaneko ◽  
Hideo Koyama ◽  
Gavin C. Stratford ◽  
Masaaki Tabuchi
Keyword(s):  
Oxide Scale ◽  
Rupture Life ◽  
High Vacuum ◽  
Creep Rupture ◽  
Test Duration ◽  
Creep Life ◽  
Destructive Testing ◽  
Creep Tests ◽  
Testing Environment ◽  
High Temperature Components

Small Punch, hereinafter designated as SP, creep test has been proposed as a semi destructive testing methodology to examine the residual creep life of high temperature components. Employing low alloy steel, a series of SP creep tests were conducted on disc specimens at 600°C in air and in high vacuum to investigate the influence of oxide scale on the creep rupture life. Thickness of the oxide scale on disc specimens in air increased with the test duration, e.g., about 30μm in thickness after 400 hours. The creep rupture life in air reduced to a half of the life in vacuum due to an increase in the actual stress in the disc thickness. In addition, the magnitude of radius of a lower die shoulder affected the SP creep rupture life. The influence of this radius on the SP creep life was also studied experimentally and numerically. The creep rupture life with the die radius of 0.5mm had twice longer than that with 0.6mm. This fact was also demonstrated by the FE analysis.

scholarly journals The Influence of Both Testing Environment and Fillet Radius of the Die Holder on the Rupture Life of Small Punch Creep Tests

2012 ◽  
Vol 6 (8) ◽  
pp. 925-934 ◽  
Author(s):  
Ken-ichi KOBAYASHI ◽  
Masahiro KANEKO ◽  
Hideo KOYAMA ◽  
Gavin C. STRATFORD ◽  
Masaaki TABUCHI
Keyword(s):  
Rupture Life ◽  
Creep Tests ◽  
Small Punch ◽  
Testing Environment ◽  
Fillet Radius

Small Punch Creep Properties of Heat Affected Zones of Reduced Activation Ferritic Steel

2008 ◽  
Author(s):  
Taichiro Kato ◽  
Shin-Ichi Komazaki ◽  
Yutaka Kohno ◽  
Hiroyasu Tanigawa
Keyword(s):  
Base Metal ◽  
Creep Test ◽  
Ferritic Steel ◽  
Electron Beam Welding ◽  
High Stress ◽  
Creep Rupture ◽  
Creep Tests ◽  
Creep Properties ◽  
Small Punch ◽  
Uniaxial Creep

The small punch (SP) creep test was carried out at the temperatures of 823∼923 K by using a further miniaturized specimen, namely, TEM disk-type specimen (φ 3.0×t0.25 mm). The tests were applied to the fine grain heat affected zone (FGHAZ), tempered HAZ (THAZ) and base metal (BM), respectively, which were removed from the joint of the reduced activation ferritic steel welded by an electron beam welding, in order to investigate the creep properties of such local regimes. The results obtained from the SP creep test were correlated with those of uniaxial creep tests using the base metal (BM) and welded joint (WJ). Experimental results revealed that there were no large differences between the SP creep rupture strengths of the FGHAZ and THAZ and that of the BM at the relatively high load levels. This result was in good agreement with the fact that the uniaxial creep strength of the WJ was almost coincident with that of the BM at the relatively high stress levels. In addition, the ratio of load (P) to stress (σ), which gave same rupture time, was calculated by using the creep rupture data of the BMs. As a result, the ratio was determined to be 0.43, resulting in the following equation; P = 0.43 σ.

scholarly journals Deformation and Fracture Mode during Small Punch Creep Tests

2009 ◽  
Vol 75 (753) ◽  
pp. 669-676 ◽  
Author(s):  
Ken-ichi KOBAYASHI ◽  
Ikumi KAJIHARA ◽  
Hideo KOYAMA ◽  
Gavin Christopher STRATFORD
Keyword(s):  
Fracture Mode ◽  
Creep Tests ◽  
Small Punch ◽  
Deformation And Fracture

PS44 Effect of Oxide Scale in Small Punch Creep Specimen on Creep Rupture Life

2010 ◽  
Vol 2010 (0) ◽  
pp. 143-145
Author(s):  
Masahiro KANEKO ◽  
Ken-ichi KOBAYASHI ◽  
Hideo KOYAMA
Keyword(s):  
Oxide Scale ◽  
Rupture Life ◽  
Creep Rupture ◽  
Small Punch ◽  
Creep Specimen

Small Punch Creep Testing Technique for Remnant Life Assessment

2014 ◽  
Vol 592-594 ◽  
pp. 739-743 ◽  
Author(s):  
J. Ganesh Kumar ◽  
K. Laha ◽  
M.D. Mathew
Keyword(s):  
Creep Test ◽  
Rupture Life ◽  
Life Assessment ◽  
Test Results ◽  
Creep Tests ◽  
Testing Technique ◽  
Creep Properties ◽  
Small Punch ◽  
Miniature Specimens ◽  
Deflection Rate

Small punch creep (SPC) testing technique is a material non-intensive testing technique for evaluating creep behavior of materials using miniature specimens. It can be used for remnant life assessment (RLA) studies on components in service, by scooping out limited material for testing without impairing the strength of component. In order to ensure the reliability of use of SPC technique for RLA, it is necessary to establish sound database on SPC properties of the material before putting into service. In this investigation, SPC technique was used to evaluate creep properties of 316LN stainless steel using specimens of size 10 x 10 x 0.5 mm. SPC tests were conducted in load controlled mode at 923 K and at various loads. SPC curves clearly exhibited primary, secondary and tertiary creep stages. The minimum deflection rate increased and rupture life decreased with an increase in applied load. Like in conventional creep test results, the minimum deflection rate obeyed Norton’s power law and Monkman-Grant relationship. SPC test was correlated with corresponding conventional creep test. Good correlation was established between creep rupture life values evaluated from SPC tests and conventional creep tests.

Study of Creep Strength for P91 Steels after Short Term Overheating above Ac3 Temperature

2013 ◽  
Vol 393 ◽  
pp. 94-101
Author(s):  
Ng Guat Peng ◽  
Badrol Ahmad ◽  
Mohd Razali Muhamad ◽  
M. Ahadlin
Keyword(s):  
High Temperature ◽  
Creep Strength ◽  
Rupture Strength ◽  
Rupture Life ◽  
Creep Rupture ◽  
Tempered Martensite ◽  
Short Term ◽  
Creep Tests ◽  
Rupture Stress ◽  
Limited Creep

Advanced ferritic steels containing 9 wt% Cr are widely used in the construction of supercritical and ultra supercritical boiler components. The microstructure of the as supplied 91 materials consists of a tempered martensite matrix, a fine dispersion of intergranular chromium rich M23C6 precipitates and intragranular carbonitrides MX particles rich in V and Nb. This steel requires post weld heat treatment (PWHT) to produce a tempered microstructure after welding to develop excellent creep strength for high temperature service. Based on past experience, situations may arise whereby the components are subjected to an accidental overshoot in temperature during PWHT. The short excursion to high temperature beyond Ac3 would have resulted in the formation of deleterious phases, for example, soft α-ferrite which has poor creep strength and hard martensite which has a low toughness. In this study, the degraded specimens with soft α ferrite as a result of cooling transformation from 900°C are proven to have a limited creep rupture life where the creep rupture strength dropped remarkably after 1000 hours. As the peak temperature increased to 950°C and 1000°C, hard and brittle martensite was formed on cooling. The creep specimens were found to exhibit better creep strength; most probably the creep behavior was improved by the tempering effect at 600°C during creep tests. Nevertheless, despite the tempering which might have improved the toughness slightly, the high temperature creep rupture stress still had dropped approximately 40%, as compared to the virgin alloys in the range of rupture time from 1,000 hours to 10,000 hours.

Microstructure Evolution and Creep Rupture Behavior of Modified 9Cr-1Mo Steel Welded Joint

2020 ◽  
Author(s):  
Facai Ren ◽  
Xiaoying Tang ◽  
Jinsha Xu ◽  
Jun Si ◽  
Yiwen Yuan
Keyword(s):  
Electron Microscope ◽  
Microstructure Evolution ◽  
Welded Joint ◽  
Rupture Life ◽  
Optical Microscope ◽  
Creep Rupture ◽  
Creep Tests ◽  
Uniaxial Creep ◽  
Before And After ◽  
Rupture Behavior

Abstract Microstructure evolution and creep rupture behavior of modified 9Cr-1Mo steel welded joint used for steam cooler in high pressure heater system were systematically studied in this paper. Creep tests were carried out using uniaxial creep specimens machined from the normalized and tempered plate at 818K and 838K with the stresses ranging from 150 to 225MPa. The curve of stress vs. rupture time was achieved to evaluate the creep rupture life of modified 9Cr-1Mo steel welded joint. The creep data were analyzed in terms of Norton’s power law, Monkman-Grant relation and modified Monkman-Grant relation. Microstructure before and after creep exposure were analyzed by optical microscope, scanning electron microscope and transmission electron microscope, to further explain the rupture mechanisms of modified 9Cr-1Mo steel welded joint.

EFFECT OF BORON ON CREEP DUCTILITY AND CREEP RUPTURE LIFE IN 9CR-1.5MO STEEL

2010 ◽  
Vol 24 (15n16) ◽  
pp. 2490-2495 ◽  
Author(s):  
BUMJOON KIM ◽  
JIWOO IM ◽  
MOON K. KIM ◽  
JONGHOON LEE ◽  
BYEONGSOO LIM
Keyword(s):  
Creep Test ◽  
Rupture Life ◽  
General Concept ◽  
Creep Rupture ◽  
Displacement Rate ◽  
Boron Addition ◽  
Creep Ductility ◽  
Small Punch ◽  
Uniaxial Creep ◽  
The Relationship

In this study, the relationship between the creep ductility and rupture life of 9 Cr -1.5 Mo steel with boron addition at 600°C was investigated by small punch (SP) creep test from the viewpoint of the modified Monkman-Grant relation. The amount of boron addition ranged from 0.0076wt% to 0.0196 wt%. The general concept of Monkman-Grant ductility for uniaxial creep was introduced and then particularly modified for the SP creep. The microstructure of the steel was observed to analyze the effect of boron addition on the creep ductility and rupture life. Based on the modified Monkman-Grant ductility for SP creep, it was found that the boron addition improved the creep ductility and rupture life of the 9 Cr -1.5 Mo steel. Also, the relationship between the minimum creep displacement rate and the amount of boron addition was analyzed.

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