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The effect of compressive residual stresses on the properties of tumbled-processed cemented carbide

Keown, Eugene Michel (2017)
M.Sc. thesis, University of Birmingham.

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For cemented carbide, classified as a brittle material, very little plastic deformation will occur preceding the initiation of a crack and ultimate failure. It is well known that compressive residual stress (CRS) helps to counteract the inherent brittle nature of cemented carbide. By focusing on rock drill inserts, a new method was used that significantly increase the depth of CRS. WC- Co composites with 11wt% Co and a mean tungsten carbide grain size of 4 micrometers were treated at different accelerations. The hardness, toughness and compressive strength were measured. A significant increase in coercivity (Hc) was recorded in the treated samples which directly related to the kinetic energy applied to the system. In samples exposed to treatment at 40G acceleration, compressive stresses were measured as deep as 6mm. In compressive strength tests, these samples showed an increase of 61% of the compressive strength. These samples have the maximum hardness increase of approximately 100 HV30 close to the treated surface. No Palmqvist cracks could be observed even at HV100. EBSD analysis showed no correlation between the Hc increase and grain refinement due to the treatment process. TEM and XRD revealed a large number of dislocations in the WC phase and Cobalt phase.

Type of Work:M.Sc. thesis.
Supervisor(s):Chiu, Yu-Lung
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:School of Metallurgy and Materials
Subjects:TN Mining engineering. Metallurgy
Institution:University of Birmingham
ID Code:7959
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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