scope:

The purpose of this Defence Standard is to provide designers and users with advice on the application of thermally sprayed coatings. It includes cleaning, preparation of surfaces, design considerations, materials to be applied, quality control, inspection, and testing.

It is not intended to apply to aerospace parts and equipment which are covered elsewhere.

This Defence Standard deals with the use of sprayed coatings to recover worn or mismachined components andor provide different surface characteristics (eg wear resistance, electrical purposes, hard-facing, corrosionloxidation resistance). It also amplifies the recommendations given in BS 4495.

The following publications may also be found useful:

Thermal Spraying. Terminology, Classification - BS EN 657

Specification for Sprayed Unfused Metal Coatings for Engineering Purposes - BS 4761

Specification for Sprayed and Fused Metal Coatings for Engineering Purposes - BS 4950

The following are typical applications:

Bearing and wearing surfaces of rotating and reciprocating components. Items may be sprayed for wear and/or corrosion resistance, with such meterials as stainless steels and other alloy steels, molybdenum, carbides, ceramics, etc.

Mating surfaces of components such as ball races, flywheels, etc, which are assembled using either shrink or interference fits, sprayed with intermetallic compounds and their derivatives, stainless steels, molybdenum, ceramics, etc.

Exhaust pipes, silencers, hot gas ducts, chimneys, and burners sprayed with aluminium, to a thickness of approximately 0.2 mm, to provide high temperature corrosion resistance up to 500°C.

Exhaust manifolds and furnace parts sprayed with aluminium to a thickness of approximately 0.2 mm sealed, and heat-treated to provide high temperature corrosion resistance up to 950°C.

For electrical screening and conductivity, items may be sprayed with copper for example. The thickness of deposit varying according to application.

Diesel engine piston heads, rocket nose cones, and exhausts coated with yttria-stabilized zirconia for thermal insulation or a fused nickel-chromium-boron coating for protection against high temperature corrosion (see section two).

'Wet' surfaces of diesel engine cylinder liners coated with alumina to withstand cavitation erosion.