Evaluation of plasma sprayed coatings as surface pretreatments for adhesive bonding

The use of plasma-sprayed coatings as surface pretreatments for adhesive bonding has been investigated. Increased pressure by the Environmental Protection Agency and other environmental groups has prompted the search for environmentally safe methods of pretreating metals before bonding. Plasma spraying techniques may offer an appropriate non-chemical-solution method to prepare metal surfaces for adhesive bonding. The technique has the capability of coating an adherend with almost any chemical compound. Plasma spraying techniques allow for optimization of coating characteristics such as thickness, porosity, and uniformity. Both the chemical and the physical properties of an adherend surface coating influence the durability performance in a bonded sample. Polymer and inorganic powders were plasma-sprayed on aluminum and titanium. Polymer powders included an epoxy, a polyester, a bismaleimide/cyanate ester mixture, and a bismaleimide/LARC TPI 1500 mixture. Inorganic powders, Al₂O₃, AIPO₄, MgO, and SiO₂ were sprayed on aluminum adherends, and TiO₂, TiSi₂, MgO, and SiO₂ were sprayed on titanium adherends. Inorganic coatings were sprayed at two different coating thicknesses. Surface analytical techniques, X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscopy/Energy Dispersive X-ray analysis (SEM/EDX), were used for the surface characterization of the plasma-sprayed adherends and failure surfaces. XPS results suggest that the chemical state of an element is sometimes altered during the plasma spraying process. SEM photomicrographs reveal various topographical differences in the sprayed coatings. All polymer powders were smooth with the exception of the bismaleimide/polyimde samples. The inorganic specimens exhibited differences in coating uniformity and surface morphology. The strength and durability of samples where the plasma-sprayed coatings were used as surface pretreatments for adhesive bonding were evaluated by loading the bonded specimens with either a peel or a shear stress and cycling the specimens through an environmental cycle that would simulate use conditions. The durability tests suggest that many of the samples prepared using thin plasma-sprayed coatings had crack growths and failure modes equivalent to reference specimens, phosphoric acid anodized aluminum and Turco 5578 treated titanium.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Chemistry

Department dc:contributor.department

Chemistry

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

1994

Author dc:creator

• Wolfe, Kristy L.

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en

Dc Identifier Other

etd-06162009-063427

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/43342