Cladding technique

In commercial practice, powdered explosives on an ammonium nitrate basis are used in most cases. Typical detonation velocities are between 1800 and 3500 m/s depending on the metal system to be bonded. The lower detonation velocity range is preferred for many metal systems in order to minimize the quantity of solidified melt associated with the bond-zone waves (12). In addition, subsonic detonation velocity explosives are required for the parallel cladding technique in order to avoid attached shock waves in the coUision region, which preclude formation of a good bond. 

The interior surfaces of the vessel are typically cladded with austenitic stainless steel. Cladding is used to prevent general corrosion by coolant and to minimize the build-up of corrosion products in the reactor coolant system. The cladding is applied in one or two layers by single-wire, multiwire or strip-cladding techniques. 

Ashley, P. R., and Tumolillo, T. A., Jr., Single-mode nonlinear channel waveguides using photopolymer cladding technique, in lEEEIOSA Proceedings on Integrated Photonics Research, Vol. 5, MF4, 1990. 

Nickel is one of the most important coating materials because it has the same strength as steel, but it is extremely resistant to corrosion. Nickel is most commonly applied electrolytically, but it can also be applied by chemical and cladding techniques. 

This type of coil was prepared from copper cladded printed circuit board material by applying photolithographic techniques. The p.c. board material is available with difierent copper thicknesses and with either a stiff or a flexible carrier. The flexible material offers the opportunity to adapt the planar coil to a curved three dimensional test object. In our turbine blade application this is a major advantage. The thickness of the copper layer was chosen to be 17 pm The period of the coil was 100 pm The coils were patterned by wet etching, A major advantage of this approach is the parallel processing with narrow tolerances, resulting in many identical Eddy current probes. An example of such a probe is shown in fig. 10. 

The preparation and assembly of clads is not amenable to automated production techniques, and each assembly requires considerable labor. 

Eabrication techniques must take into account the metallurgical properties of the metals to be joined and the possibiUty of undesirable diffusion at the interface during hot forming, heat treating, and welding. Compatible alloys, ie, those that do not form intermetaUic compounds upon alloying, eg, nickel and nickel alloys (qv), copper and copper alloys (qv), and stainless steel alloys clad to steel, may be treated by the traditional techniques developed for clads produced by other processes. On the other hand, incompatible combinations, eg, titanium, zirconium, or aluminum to steel, require special techniques designed to limit the production at the interface of undesirable intermetaUics which would jeopardize bond ductihty. 

Vessel heads can be made from explosion-bonded clads, either by conventional cold- or by hot-forming techniques. The latter involves thermal exposure and is equivalent in effect to a heat treatment. The backing metal properties, bond continuity, and bond strength are guaranteed to the same specifications as the composite from which the head is formed. AppHcations such as chemical-process vessels and transition joints represent approximately 90% of the industrial use of explosion cladding. 

Pig. 10. Double-v inlay, batten-strap technique for fusion welding of an explosion-clad plate containing titanium and zirconium. 

Cladding may be less expensive than selective electro deposition when coatings greater than 1 p.m of a noble metal are required, but may be more expensive than electro deposition for thinner coatings. Selective techniques are most easily used for sheet metal substrates that are to be machine stamped and formed into contacts. Clad noble metals are considerably more ductile (and less hard) than comparable electro deposits and, therefore, are better suited to forming operations. Contacts that are made into separate parts from rod by screw machining are usually coated on all exposed surfaces by barrel electroplating. 

Re-use of cladding or other construction materials smoke ventilation, drainage, fire detection/suppression systems or techniques to reflect the existing installations may not comply with current requirements, particularly with respect to ... 

Insulation is one of those ubiquitous techniques that is always around, always impinging on our work, social and domestic activities and yet for most of the time is hardly noticed. Insulation is a passive product once installed, it works efficiently, quietly and continually, usually out of sight, enclosed within a structure or a casing or under cladding. 

Although molybdenum is resistant to molten glass, except leaded, molybdenum components not coated with glass but exposed to the oxidising furnace atmosphere corrode rapidly due to volatilisation of molybdenum oxide above 370°C. To overcome this, stirrers etc. for use in glass plant are physically clad with platinum sheet in vulnerable areas. Modern plating techniques have enabled dense platinum coatings to be put onto the surface of the molybdenum and it is expected that this technique will be exploited further in the near future. 

Flame sprayed molybdenum articles have poor corrosion resistance, no doubt owing to the porosity of the coating. However, modern plasma spraying techniques produce a dense coating and this should lead to more widespread use of clad materials such as molybdenum clad steel where the clad product should have the same corrosion resistance as the solid material. 

P.V.C. is used extensively in the building industry for external cladding and internal partitions. It is used because it has excellent weathering properties and will protect the substrate against corrosion for periods in excess of 10 years. When it is applied at a thicknesses of about 200 /tm it can withstand the hard handling techniques often associated with building sites. 

An application of increasing importance is in the cladding of metals. In this a layer of explosive is used to project the cladding on to the base metal at such a speed that the two become firmly welded together. Fig. 14.13 shows one technique for small items where the cladding is at an angle to... 

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