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Title: JOINING OF MOLYBDENUM DISILICIDE TO STAINLESS STEEL USING AMORPHOUS METAL BRAZES-RESIDUAL STRESS ANALYSIS

Abstract

Molybdenum disilicide (MoSi{sub 2})/stainless steel 316 L jOints were produced by high temperature brazing using a cobalt-based metallic-glass (METGLAS{trademark} 2714A). Successful joining was completed in two different ways; either by feeding excess braze into the braze gap upon heating or by constraining the MoSi{sub 2}/stainiess steel assembly with an alumina (Al{sub 2}O{sub 3}) fixture during the heating cycle. These steps were necessary to ensure the production of a high quality void free joint. Residual stress measurements were completed on these joints. Indentation results show higher tensile residual stresses in the stainless steel for the joint with the external constraint, in comparison to the unconstrained state. In contrast, the compressive residual stresses In the MoSi{sub 2} (as measured by X-ray diffraction) were lower in the constrained state relative to the unconstrained state. These results and a lack of residual stress balance indicate that the stress state in the braze is significantly different under the two joining conditions and the volume of the braze plays an important role in the development of the residual stresses. Push-out tests carried out on these joints gave higher joint strengths in the unconstrained as compared to the constrained condition. The results of this study have importantmore » implications on the selection of the appropriate joining process (use of constraint versus extra braze).« less

Authors:
 [1];  [1];  [1]
  1. Los Alamos National Laboratory
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
OSTI Identifier:
985892
Report Number(s):
LA-UR-07-0652
TRN: US201017%%70
DOE Contract Number:
AC52-06NA25396
Resource Type:
Conference
Resource Relation:
Conference: DVS-LOT GERMAN WELDING SOCIETY ; 200706 ; AACHEN
Country of Publication:
United States
Language:
English
Subject:
36; BRAZING; FEEDING; HEATING; MOLYBDENUM; PRODUCTION; RESIDUAL STRESSES; STAINLESS STEELS; STEELS; STRESS ANALYSIS; WELDING; X-RAY DIFFRACTION

Citation Formats

VAIDYA, RAJENDRA U, KAUTZ, DOUGLAS D., and GALLEGOS, DAVID E. JOINING OF MOLYBDENUM DISILICIDE TO STAINLESS STEEL USING AMORPHOUS METAL BRAZES-RESIDUAL STRESS ANALYSIS. United States: N. p., 2007. Web.
VAIDYA, RAJENDRA U, KAUTZ, DOUGLAS D., & GALLEGOS, DAVID E. JOINING OF MOLYBDENUM DISILICIDE TO STAINLESS STEEL USING AMORPHOUS METAL BRAZES-RESIDUAL STRESS ANALYSIS. United States.
VAIDYA, RAJENDRA U, KAUTZ, DOUGLAS D., and GALLEGOS, DAVID E. Tue . "JOINING OF MOLYBDENUM DISILICIDE TO STAINLESS STEEL USING AMORPHOUS METAL BRAZES-RESIDUAL STRESS ANALYSIS". United States. doi:. https://www.osti.gov/servlets/purl/985892.
@article{osti_985892,
title = {JOINING OF MOLYBDENUM DISILICIDE TO STAINLESS STEEL USING AMORPHOUS METAL BRAZES-RESIDUAL STRESS ANALYSIS},
author = {VAIDYA, RAJENDRA U and KAUTZ, DOUGLAS D. and GALLEGOS, DAVID E.},
abstractNote = {Molybdenum disilicide (MoSi{sub 2})/stainless steel 316 L jOints were produced by high temperature brazing using a cobalt-based metallic-glass (METGLAS{trademark} 2714A). Successful joining was completed in two different ways; either by feeding excess braze into the braze gap upon heating or by constraining the MoSi{sub 2}/stainiess steel assembly with an alumina (Al{sub 2}O{sub 3}) fixture during the heating cycle. These steps were necessary to ensure the production of a high quality void free joint. Residual stress measurements were completed on these joints. Indentation results show higher tensile residual stresses in the stainless steel for the joint with the external constraint, in comparison to the unconstrained state. In contrast, the compressive residual stresses In the MoSi{sub 2} (as measured by X-ray diffraction) were lower in the constrained state relative to the unconstrained state. These results and a lack of residual stress balance indicate that the stress state in the braze is significantly different under the two joining conditions and the volume of the braze plays an important role in the development of the residual stresses. Push-out tests carried out on these joints gave higher joint strengths in the unconstrained as compared to the constrained condition. The results of this study have important implications on the selection of the appropriate joining process (use of constraint versus extra braze).},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Jan 30 00:00:00 EST 2007},
month = {Tue Jan 30 00:00:00 EST 2007}
}

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  • Neutron diffraction was used to measure the bulk residual strains in molybdenum disilicide (MoSi{sub 2})-316L stainless steel joints. The joints were produced by brazing disks of MoSi{sub 2} and 316L stainless steel along with an interlayer, using Cusil{trademark} as the braze. This study explored the physical parameters of the interlayer on the average phase strains in the MoSi{sub 2} and 316L stainless steel. The effect of the coefficient of thermal expansion was explored by using three different interlayer materials: niobium, nickel, and nickel-iron. The residual strains in MoSi{sub 2} decreased significantly in both radial and axial directions with increasing niobiummore » interlayer thickness. Residual strains were relatively insensitive to changes in 500 {micro}m thick interlayer material. Finite element modeling results were corroborated by the neutron measurements on the joints allowing inferences to be drawn concerning the preference of the interlayer material. The results illustrate the importance of the ductile interlayer in the successful fabrication of MoSi{sub 2}-316L stainless steel joints.« less
  • Creep-induced stress relaxation of a braze alloy can be an important factor in successful processing of certain metal/ceramic braze joint geometries where there is a mismatch in thermal expansion. The inclusion of a creep constitutive law in finite element analysis (FEA) codes makes it possible to calculate the effect of a particular cooling rate from the braze temperature on residual stresses in the ceramic. Valid calculations require a constitutive law for creep of the brazement which accurately predicts the minimum strain rate over a wide range of temperatures. Using data from previous investigations on the creep of recrystallized Cu, wemore » have developed minimum strain rate creep correlations at both high and intermediate temperatures for pure Cu. At the higher temperatures, a power law is used, with the activation energy obtained by regression analysis quite close to the value of lattice self diffusion in Cu. At intermediate temperatures (350-600{degree}C), we have found that the Garofalo sinh equation obtains the best fit to the data, with an activation energy approximately equal to 2/3 of the activation energy for lattice diffusion, attributable to dislocation core diffusion. Results for FEA calculations of the residual stresses obtained in Cu brazing of a metallic feedthrough pin to a metallized alumina ceramic are presented using both time-independent and creep constitutive laws for pure Cu. At higher temperatures, the creep law predicts lower residual stresses in the alumina compared to the elastic/plastic constitutive law. However, at lower temperatures, the results obtained with the elastic/plastic constitutive law indicate lower stress levels in the ceramic compared to the predictions obtained with the various creep constitutive relations. The lower temperature results are discussed in the context of primary creep behavior. 23 refs., 14 figs.« less
  • Residual stresses in a body arise from nonuniform plastic deformation and continue to be an important consideration in the design and the fabrication of metal components. The finite element method offers a potentially powerful tool for predicting these stresses. However, it is important to first verify this method through careful analysis and experimentation. This paper describes experiments using neutron and x-ray diffraction to provide quantitative data to compare to finite element analysis predictions of deformation induced residual stress in a plane stress austenitic stainless steel ring. Good agreement was found between the experimental results and the numerical predictions. Effects ofmore » the formulation of the finite element model on the analysis, constitutive parameters and effects of machining damage in the experiments are addressed.« less
  • This paper is dedicated to the thorough experimental analysis of the residual stresses in the vicinity of tubular welds and the mechanisms involved in their formation. Pipes made of a ferritic-pearlitic structural steel and an austenitic stainless steel are investigated in this study. The pipes feature a similar geometry and are MAG welded with two passes and comparable parameters. Residual strain mappings are carried out using X-ray and neutron diffraction. The combined use of both techniques permits both near-surface and through-wall analyses of the residual stresses. The findings allow for a consistent interpretation of the mechanisms accounting for the formationmore » of the residual stress fields due to the welding process. Since the results are similar for both materials, it can be concluded that residual stresses induced by phase transformations, which can occur in the structural steel, play a minor role in this regard.« less
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