Microstructural changes during long time service exposure of udimet 500 and nimonic 115

1983 ◽  
Vol 14 (1) ◽  
pp. 183-189 ◽  
Author(s):  
A. K. Koul ◽  
W. Wallace
Keyword(s):  
Time Service ◽  
Microstructural Changes ◽  
Long Time ◽  
Service Exposure ◽  
Nimonic 115

The Influence of Simulated Service Exposure on the Rupture Strengths of Grade 11, Grade 22, and Type 304 Steels

1974 ◽  
Vol 96 (1) ◽  
pp. 10-21
Author(s):  
D. J. Wilson
Keyword(s):  
High Temperature ◽  
Present Stage ◽  
Time Service ◽  
Type Reaction ◽  
Stage Of Development ◽  
Straight Line ◽  
Long Time ◽  
Service Exposure ◽  
Type 304 ◽  
Grade 11

High temperature exposures were carried out to simulate long-time service. Rupture curves for exposed Grade 11 and Grade 22 steels did not exhibit the instabilities characteristic of the unused materials so that straight-line extrapolation gave good predictions of long-time strengths. Possibly due to a C-type reaction, strength predictions were poorer for Type 304 steel. Similar strengths were obtained using parameter tests of the unused materials. At the present stage of development, simulated service exposures offer an alternative, but not a superior, technique for extrapolating rupture characteristics.

The Creep of Natural and Snythetic Rubber Compounds in Shear

1941 ◽  
Vol 14 (2) ◽  
pp. 433-443 ◽  
Author(s):  
Stuart H. Hahn ◽  
Ivan Gazdik
Keyword(s):  
Processing Technique ◽  
Creep Tests ◽  
Time Service ◽  
Wide Range ◽  
Recent Developments ◽  
Long Time ◽  
The Many ◽  
Short Time ◽  
Relative Creep ◽  
Rubberlike Materials

Abstract Creep tests, extending in some cases as long as 900 days, indicate that both natural and synthetic rubbers such as Neoprene and butadiene copolymer can be compounded to give satisfactory service in shear mountings. At 140° F, creep is from two to nine times greater than at 80° F, depending on the compound. Tests at room temperature do not indicate either the amount of creep or the life to be expected at higher temperatures. Actual creep (measured in inches) increases with stress, but when expressed at percentage of initial deflection, it may be independent of stress. Creep curves are linear over a considerable range of time when plotted on log-log scales. However, extrapolation of such curves to predict results after very long times is not justified, because the curves may not continue to be linear, or failure of the mountings may occur, particularly at high temperatures. Short time tests of any sort are not necessarily indicative of the relative creep or life of compounds in long-time service. The tests reported here are a small portion of a large number which is being continued and augmented. It is hoped that these and other investigations now under way may contribute to clearing the picture of the complex interrelations between the many physical properties of compounds of rubberlike materials. The rubber technologist uses his specialized knowledge to develop a wide variety of compounds, making use of several types of basic rubberlike materials. He chooses whichever fits service requirements best from performance and economic viewpoints. Modern materials and recent developments in processing technique have made possible compounds suitable for a wide range of service conditions.

scholarly journals Microstructure Evolution and Failure Behavior of Stellite 6 Coating on Steel after Long-Time Service

Coatings ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 532 ◽  
Author(s):  
Jiankun Xiong ◽  
Fuheng Nie ◽  
Haiyan Zhao ◽  
Liangliang Zheng ◽  
Jun Luo ◽  
...  
Keyword(s):  
Fusion Zone ◽  
Microstructure Evolution ◽  
Failure Behavior ◽  
Micro Hardness ◽  
Time Service ◽  
Stellite 6 ◽  
Long Time ◽  
Metallic Compounds ◽  
Hardness Increase ◽  
Stellite Coating

The microstructure evolution, elements diffusion and fracture behavior of the Stellite 6 weld overlay, deposited on 10Cr9Mo1VNbN (F91) steel by the tungsten inert gas (TIG) cladding process, were investigated after long-time service. Obvious diffusion of Fe occurred from the steel and fusion zone to the Stellite overlay, resulting in the microstructure evolution and hardness increase in the coating, where hard Co–Fe phases, σ phases (Fe–Cr metallic compounds) and Cr-rich carbides (Cr18.93Fe4.07C6) were formed. Besides, the width of the light zone, combined with the fusion zone and diffusion zone, increased significantly to a maximum value of 2.5 mm. The fracture of the Stellite coating samples mainly occurred in the light zone, which was caused by the formation and growth of circumferential crack and radial crack under high temperature and pressure conditions. Moreover, the micro-hardness values in the light zone increased to the maximum (470–680 HV) due to the formation and growth of brittle Co–Fe phases. The formation of these cracks might be caused by formed brittle phases and changes of micro-hardness during service.

A Comparison of Some Carbon Molybdenum Steels on the Basis of Various Creep Limits

1948 ◽  
Vol 159 (1) ◽  
pp. 165-172 ◽  
Author(s):  
A. E. Johnson ◽  
H. J. Tapsell
Keyword(s):  
Experimental Study ◽  
Experimental Work ◽  
Carbon Steels ◽  
Prolonged Heating ◽  
Time Service ◽  
Long Time ◽  
Engineering Materials ◽  
Short Time ◽  
The Relationship ◽  
Creep Limits

A previous report gave the results of an experimental study of the relationship between short-time and long-time creep limits of a number of carbon steels. Certain conclusions were drawn which it was realized were not necessarily applicable to other types of steel. Similar experimental work has since been carried out on six carbon molybdenum steels, and the results obtained indicate similar limitations in the applicability of short-time creep limits to estimation of design stresses for long-time service, as were disclosed by the prior tests on carbon steels. There is not, at first sight, any reason why short-time and long-time creep limits should correlate, since with most engineering materials metallurgical changes occur during prolonged heating.

Effects of Long-Time Service on the Material of a Steam Boiler Fire Tube

1998 ◽  
Vol 40 (1) ◽  
pp. 43-48 ◽  
Author(s):  
D.T Levcovici ◽  
V Munteanu ◽  
S.M Levcovici ◽  
M Ursu
Keyword(s):  
Steam Boiler ◽  
Time Service ◽  
Long Time

Influence of Service Time on the Microstructure and High Temperature Mechanical Properties of T23 Boiler Tube

2017 ◽  
Vol 898 ◽  
pp. 711-718 ◽  
Author(s):  
Cheng He ◽  
Bao Liang Shi ◽  
Wen Sheng Li ◽  
Jian Ping Zhao ◽  
Kai Xu ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
High Temperature ◽  
Service Time ◽  
Testing Machine ◽  
Tensile Testing Machine ◽  
Time Service ◽  
High Temperature Mechanical Properties ◽  
The Matrix ◽  
Long Time

The influence of long time service on the microstructure and high temperature mechanical properties of T23 steel was studied by optical microscopy, scanning electron microscopy, transmission electron microscopy and tensile testing machine. Results showed that lathy bainite ferrite disappears with the increasing service time, both the size and number of the carbides increases, and M23C6 carbides transform into M6C carbides rich in W element. The service process also has a significant influence on the recovery. Sub-grains were found at the grain boundaries with little dislocations in the matrix after 27448 h service time. After running for 27448 h the microstructure degradation of T23 steel is serious. High temperature tensile properties of T23 are closely related to the alloy aging degree. The reasons for the decrease of high temperature mechanical properties after long time service included microstructure degradations such as the increase of both the size and quantity of M23C6 carbides, the transformation of M23C6 to M6C, the desolution of Cr,W,and Mo elements, the decrease of the dislocation density and the occurrence of the sub-grains.

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