Comparison between shot peening and abrasive blasting processes as deposition methods for hydroxyapatite coatings onto a titanium alloy

Title: Comparison between shot peening and abrasive blasting processes as deposition methods for hydroxyapatite coatings onto a titanium alloy
Authors: Byrne, Greg
O'Neill, Liam
Twomey, Barry
Dowling, Denis P.
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Date: 15-Feb-2013
Online since: 2014-01-23T09:28:00Z
Abstract: Recent studies have shown that combining a compressed air jet with entrained hydroxyapatite (HA) particles with a jet of abrasive particles can be used to deposit a well adhered crystalline HA coatings onto titanium substrates. A similar particle bombardment process utilising a flow of shot peen particles and a flow of suitable powder particles has been used to deposit a range of coatings, though the deposition of bioceramic powders have not yet been reported by this method. In this study a direct comparison between the shot peen and abrasive bombardment processes has been undertaken to determine which technique yields coatings exhibiting higher levels of adhesion on titanium alloy substrates. Both processes were shown to effectively deposit a layer of crystalline apatite onto the titanium substrates over a range of pressures and jet to substrate heights. It was observed that for both processes that an increase in particle kinetic energy producing corresponding enhancements in both deposition rate and surface roughness. The shot peen process however produced a smooth layer of laminar apatite, which was readily removed from the surface using a scratch adhesion test technique. In contrast the combination of a jet of HA and abrasive powders resulted in an increase in surface abrasion and increased mechanical interlocking of the HA into the metal surface was observed. The mechano-chemical affect achieved resulted in a better adhered HA layer. The surface morphology obtained using the two treatments was significantly different with an increase in the average roughness (Ra) of ≈ 70 and 80 % for samples treated with abrasive particles over shot peen. This difference in surface treatment is further highlighted by the removal of the HA using an acid etch. The roughness (Ra) of the underlying titanium layer after this removal is, on average, >175 % higher for the surface treated with the abrasive particles during HA deposition.
Funding Details: Science Foundation Ireland
Type of material: Journal Article
Publisher: Elsevier
Journal: Surface and Coatings Technology
Volume: 216
Start page: 224
End page: 231
Copyright (published version): 2012 Elsevier B.V.
Keywords: HydroxyapatiteShot peenGrit blastAbrasiveCrystallineBioceramic
DOI: 10.1016/j.surfcoat.2012.11.048
Language: en
Status of Item: Peer reviewed
Appears in Collections:Mechanical & Materials Engineering Research Collection

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