scholarly journals Grain Boundary Damage Evolution and Rupture Life of Service-exposed 1.25Cr-0.5Mo Steel Welds

2003 ◽  
Vol 43 (12) ◽  
pp. 2054-2061 ◽  
Author(s):  
Shimpei Fujibayashi
Keyword(s):  
Grain Boundary ◽  
Damage Evolution ◽  
Rupture Life ◽  
Steel Welds

Finite-Element Analysis of Waspaloy Using Sinh Creep-Damage Constitutive Model Under Triaxial Stress State

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
Mohammad Shafinul Haque ◽  
Calvin Maurice Stewart
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Creep Deformation ◽  
Damage Evolution ◽  
Rupture Life ◽  
Creep Damage ◽  
Nickel Base Superalloy ◽  
Element Analysis ◽  
Stress Levels ◽  
Nickel Base

The creep deformation and damage evolution of nickel base superalloy (Waspaloy) at 700 °C are studied using the classic Kachanov–Rabotnov (KR) and a recently developed Sin-hyperbolic (Sinh) model. Uniaxial creep deformation and Bridgman rupture data collected from literature are used to determine the model constants and to compare the KR and the Sinh solutions. Finite-element (FE) simulations on a single eight-node element are conducted to validate the accuracy of the FE code. It is observed that KR cannot predict the creep deformation, damage, and rupture life of nickel base superalloys accurately using one set of constants for all the stress levels. The Sinh model exhibits a superior ability to predict the creep behavior using one set of constants for all the stress levels. Finite-element analysis (FEA) on 3D Bridgman notched Waspaloy specimen using the Sinh model is conducted. The results show that the Sinh model when combined with a representative stress equation and calibrated with experimental data can accurately predict the “notch effect” observed in the rupture life of notched specimen. Contour plots of damage evolution and stress redistribution are presented. It is demonstrated that the Sinh model is less stress sensitive, produces unconditional critical damage equal to unity at rupture, exhibits a more realistic damage distribution around the crack tip, and offers better crack growth analysis than KR.

The Evolution of Prior-BCC Grain Boundary Cracking During In-situ Creep Deformation of a Ti-15Al-33Nb(at%) Alloy

2006 ◽  
Vol 980 ◽  
Author(s):  
Christopher J. Cowen ◽  
Carl J. Boehlert
Keyword(s):  
Grain Boundary ◽  
Damage Evolution ◽  
Damage Accumulation ◽  
Vacuum Chamber ◽  
Creep Damage ◽  
Sample Surface ◽  
Tensile Creep ◽  
Backscattered Electron ◽  
Scanning Electron

AbstractIn-situ tensile-creep experiments were performed on a Ti-15Al-33Nb(at%) alloy using a specialized tensile stage placed within the vacuum chamber of a Camscan 44 FE scanning electron microscope (SEM). The creep damage evolution on the sample surface was chronicled through backscattered electron (BSE) imaging as a function of stress, time, and creep displacement at 650°C. The experiments revealed that the prior-BCC grain boundaries were the locus of damage accumulation during creep and significant grain boundary cracking was observed. The grain boundary cracking was verified to occur within the bulk of the material through post-mortem analysis.

Heat Treated Microstructure and Mechanical Properties of K492M Alloy

2014 ◽  
Vol 788 ◽  
pp. 493-497
Author(s):  
Xiang Hui Li ◽  
Lian Li ◽  
Xin Tang ◽  
Qi Dong Gai
Keyword(s):  
Mechanical Properties ◽  
Grain Boundary ◽  
Interdendritic Region ◽  
Rupture Life ◽  
Stress Rupture ◽  
Stress Rupture Life ◽  
Stress Rupture Properties ◽  
Heat Treated ◽  
Columnar Grain ◽  
Rupture Properties

The microstructure, tensile and stress rupture properties of K492Malloy have been investigated in the present study. The results revealed that γ matrix, γ′ phase, carbide and eutectic in the interdendritic region within grain interior and along grain boundary were observed after solidification. After heat treatment, γ' precipitates with two obviously distinct size existed in the dendrite core and interdendritic region, respectively. Meanwhile, the chain-like (W, Mo)6C and Cr23C6carbides precipitated along grain boundary. The investigation of mechanical properties suggested that the tensile strength was initially increased but then decreased with increasing the temperature from 25oC to 760oC. The stress rupture life was 68.2h and 35.8h at 760oC / 655MPa and 870oC / 365MP, respectively. The columnar grain and carbide along grain boundary resulted in intergranular brittle fracture in both test conditions. As a result, the elongation under the conditions of 760oC/655MPa and 870oC/365MP was 1.5% and 1.4%, respectively.

Effect of Low-Angle Boundary on Microstructure and Stress Rupture Property of a Third Generation Single Crystal Superalloy DD10

2017 ◽  
Vol 898 ◽  
pp. 498-504
Author(s):  
Hui Fen Li ◽  
Li Jun Liu ◽  
Ming Xue ◽  
La Mei Cao
Keyword(s):  
Grain Boundary ◽  
Single Crystal ◽  
Rupture Life ◽  
Stress Rupture ◽  
Chain Structure ◽  
Single Crystal Superalloy ◽  
Third Generation ◽  
Stress Rupture Life ◽  
Stress Rupture Property ◽  
Remarkable Effect

The microstructure of a third generation single crystal superalloy DD10 with 0°~15° grain boundary and stress rupture property at 980°C/280MPa and 1100°C/140MPa have been studied and compared in the present investigation. The results showed that the primary dendritic stems at either side of low angle boundary indicated angular differences as compared with structure of principal [001] crystal. After thermal treatment, the grain boundary changed from irregular chain structure of γ’ and γ to flat and thin γ layer. Under the condition of 980°C/280MPaand 1100°C/140MPa, stress rupture life of the DD10 alloy with 7° low angle boundary decreased little compared with [001] crystal. The rupture was non-intergranular fracture. The 9° low angle boundary did not have a remarkable effect on stress rupture property of the DD10 alloy.

Effect of Minor Elements on the Grain Boundary Strengthening of a Single Crystal Superalloy RR2072

2007 ◽  
Vol 124-126 ◽  
pp. 1405-1408
Author(s):  
D.H. Kim ◽  
Y.S. Yoo ◽  
Chang Yong Jo ◽  
C.N. Jones
Keyword(s):  
Grain Boundary ◽  
Single Crystal ◽  
Rupture Life ◽  
Stress Rupture ◽  
Thermal Exposure ◽  
Single Crystal Superalloy ◽  
M23c6 Carbide ◽  
Carbide Formation ◽  
Minor Elements ◽  
Grain Boundary Strengthening

Effect of carbon and boron on the grain boundary strengthening of a second generation single crystal superalloy RR2072 was investigated. Single crystal and bicrystal specimen with three kinds of tilt type misorientation angle were grown by Bridgman technique. Creep and stress rupture tests were conducted at 950oC and 1050oC. Rupture life of single crystal of the alloy modified with carbon and boron was comparable to that of the RR2072 which is free from boron and carbon. TCP phase precipitation such as sigma was suppressed in the modified alloy during thermal exposure and creep deformation. Rupture life of the modified alloy bicrystal was superior to that of the RR2072 bicrystal. M23C6 carbide formation and suppression of γ′ band growth is thought to be the role of minor elements for the grain boundary strengthening of a nickel base single crystal superalloy RR2072.

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