Thermomechanical Surface Treatment

Svuface treatments discussed in this article include scale removal, polishing, btiffing, plating, conversion coatings, thermal spray, vapor deposition, and thermomechanical surface treatment. Titanium alloys generally do not reqvdre special surface treatments to improve corrosion resistance, because their resistance to many corrosive environments is excellent. However, titanium is coated or plated with corrosion-resistant metals (e.g., copper and platinum) as an alternative to oxide formation. 

Some examples of applications of neutron and synchrotron radiation diffraction applied to the determination of residual stresses in various industrial and technological components have been presented. The reliability of the technique has been shown, being able to determine residual stresses induced by various thermomechanical treatments, such as shrink-fit joints, welds and surface treatments in automotive and aerospace materials. It has been shown how, by this method, it is possible to determine stresses both in the coating and in the substrate of plasma-spray deposed hydroxyapatite layers on Ti alloy for biomedical applications. 

A layer with a high specific surface area could be developed on woven glass fiber supports by leaching the nonsilica components out of commercial fabrics in acidic solution [54,62], This treatment created mesoporosity and specific surface areas between 5 and 275 m2 g, depending on the temperature and the contact time with HCI solution. In some cases, the surface of porous glass fibers was modified by titania, zirconia, or alumina to increase the thermomechanical stability and to vary the surface reactivity. The modification was made by impregnation of the porous glass fibers with aqueous solutions of the appropriate salts and subsequent calcinations in air. 

Physical modification involves thermal treatments such as plasma or nonthermal treatments like application of electric discharge, ultrasound, ultraviolet, or high-frequency cold plasma to the fiber surface. Stmctural and surface properties of the fibers are changed by these treatments, which result in improved mechanical bonding to polymers. These treatments are apphed to separate the fiber bundles into individual filaments and modify the fiber surface for more compatibility with the matrix in the composite [6]. If separation of the fiber bundles is desired, methods like steam explosion and thermomechanical processing are adopted. Methods like plasma (thermal) treatment, dielectric barrier techniques, or corona discharge (nonthermal) treatments (CDT) are anployed to modify the fiber surface. 

Essentially, physical methods are employed on natural fiber during processing in order to separate natural fiber bundles into individual filaments and also to modify the surface structure of the fibers so as to improve the use of natural fibers in composites. Physical methods can be divided into two categories viz (1) steam explosion and thermomechanical processes and (2) plasma, dielectric barrier techniques, radiation modification, ultrasonic treatment, and corona discharge. In an effort to impart and improve reactivity, these physical treatments have been used to modify thermoplastic polymeric films like polyethylene and polypropylene and thermosets, such as epoxy. 

---