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Permanent link (DOI): https://doi.org/10.7939/R3K64Q

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Homogeneity of metal matrix composites deposited by plasma transferred arc welding Open Access

Descriptions

Other title
Subject/Keyword
plasma transferred arc welding
metal matrix composite
overlay
model
solidification
tungsten carbide
PTAW
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Wolfe, Tonya Brett Bunton
Supervisor and department
Henein, Hani (Chemical and Materials Engineering)
Examining committee member and department
Gerlich, Adrian (Chemical and Materials Engineering)
Yeung, Anthony (Chemical and Materials Engineering)
Ravindran, Ravi (Mechanical and Industrial Engineering, Ryerson University)
McDonald, Andre (Mechanical Engineering)
Department
Department of Chemical and Materials Engineering
Specialization

Date accepted
2010-04-14T20:20:17Z
Graduation date
2010-06
Degree
Doctor of Philosophy
Degree level
Doctoral
Abstract
Tungsten carbide-based metal matrix composite coatings are deposited by PTAW (Plasma Transferred Arc Welding) on production critical components in oil sands mining. Homogeneous distribution of the reinforcement particles is desirable for optimal wear resistance in order to reduce unplanned maintenance shutdowns. The homogeneity of the coating can be improved by controlling the heat transfer, solidification rate of the process and the volume fraction of carbide. The degree of settling of the particles in the deposit was quantified using image analysis. The volume fraction of carbide was the most significant factor in obtaining a homogeneous coating. Lowering the current made a modest improvement in homogeneity. Changes made in other operational parameters did not effect significant changes in homogeneity. Infrared thermography was used to measure the temperature of the surface of the deposit during the welding process. The emissivity of the materials was required to acquire true temperature readings. The emissivity of the deposit was measured using laser reflectometry and was found to decrease from 0.8 to 0.2 as the temperature increased from 900°C to 1200°C. A correction algorithm was applied to calculate the actual temperature of the surface of the deposit. The corrected temperature did increase as the heat input of the weld increased. A one dimensional mathematical model of the settling profile and solidification of the coatings was developed. The model considers convective and radiative heat input from the plasma, the build-up of the deposit, solidification of the deposit and the settling of the WC particles within the deposit. The model had very good agreement with the experimental results of the homogeneity of the carbide as a function of depth. This fundamental model was able to accurately predict the particle homogeneity of an MMC deposited by an extremely complicated process. It was shown that the most important variable leading to a homogeneous coating is to operate at the packing saturation limit of the reinforcement. In the case of the MMC explored, a fully homogeneous coating was obtained with 50 vol% WC in a NiCrBSi matrix.
Language
English
DOI
doi:10.7939/R3K64Q
Rights
License granted by Tonya Wolfe (tbwolfe@ualberta.ca) on 2010-04-14T04:01:13Z (GMT): Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of the above terms. The author reserves all other publication and other rights in association with the copyright in the thesis, and except as herein provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
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