High quality surface preparation prior to PVD coating

Citation

(2004), "High quality surface preparation prior to PVD coating", Aircraft Engineering and Aerospace Technology, Vol. 76 No. 3. https://doi.org/10.1108/aeat.2004.12776cab.002

High quality surface preparation prior to PVD coating

High quality surface preparation prior to PVD coating

Keywords: Surface preparation, Coatings, Aircraft

One of the world's leading specialists in advanced physical vapour deposition (PVD) coating and ion implantation technology, Tecvac Ltd, Swavesey, Cambridge (a Wallwork Group company), has recently installed the latest “Ventus 92PR” pressure-fed dry abrasive blasting cabinet machine from Vacu-Blast International, part of the International Surface Preparation Corporation (ISPC).

The machine was introduced specifically for the dedicated surface preparation of titanium and nickel alloy based aeroengine components. These are PVD coated to enhance their resistance to wear: titanium alloy components, mainly turbine compressor blades, are titanium-nitride (TiN) coated, and nickel alloy parts are chromium nitride (CrN) coated.

The Ventus machine is used to remove the “dead surface layer”, which results from heat treatment, and simultaneously create the optimum surface key for the PVD coating to adhere successfully. Following trials at the ISPC sample processing and demonstration facility in Birmingham, the powerful pressure-fed Ventus blasting system was selected to facilitate the fastest possible processing of the surface. This minimises any potential adverse modification of the existing substrate, particularly when parts have been shot peened after heat treatment. The parts are retained in tailored polyurethane fixtures, with pink alumina media being used for the blasting operation, which is carried out manually.

To ensure a consistent surface result, Ventus TR' models feature a high integrity, in-cycle blast media recovery and separation system, housed in a separate free-standing “power-pack”, allowing the machine to be used for the most demanding, precision surface treatment applications, with most types of media. The power-pack can be situated on either side of the machine to facilitate installation in virtually any location. The machine's processing enclosure measures 900 × 800 × 800 mm high. To minimise any risk when working with titanium parts, the machine at Tecvac includes special over-pressure relief panels.

The machine's large 640 × 740 mm access door has been designed to eliminate dust spillage and is safety-interlocked, and the blast enclosure features a raised workplate which avoids potential damage to the door seal when loading and unloading the machine.

The media recovery and separation system automatically separates out and recycles reusable blast media back to the blast nozzle. A COSHH- compliant reverse-jet dust collector with quick- release filter cartridges is used to collect degraded media, dust and debris.

The dust collector provides pulsing of the cartridges whilst the machine is operating, to ensure that they are cleaned as efficiently as possible. A special isolating system is also included to enable optional downtime pulsing of the cartridges following heavy dust removal applications.

Tecvac

In addition to providing advanced-technology coating services, Tecvac manufactures PVD coating systems for the production of hard coatings on tooling, moulds and a wide variety of precision engineered components. These machines are functional and robust, and incorporate the latest process automation and control systems. The company also produces industrial-scale ion implanters for specialised surface modification applications. With an increasing demand for its contract coating services, driven largely by the need for less environmentally damaging engineering coating processes and the growing use of wear-resistant surface treatments, the company is currently adding additional production capacity at its Swavesey site.

Details available from: Vacu-Blast International. Tel: +44(0) 1753 526511; Fax: +44(0) 1753 538093; E-mail: info@vacu-blast.co.uk; Web site: www.surfacepreparation.com