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HANDFACING WELDING PROCESSES |
Gas Tungsten ARC (TIG)
This process is ideally suited to facing small components, since it allows a high degree of control over heat input and the positioning of the arc and weld deposit. In common with other arc surfacing methods, the GTA (TIG) process is amenable to automation. Acceptable levels of dilution are generally considered to be less than 15%. |
Oxy-Acetylene Welding |
 Suitable for most steels and good quality cast iron, oxy-acetylene may be used to apply most cobalt alloys and some iron base and carbide containing grades. It is not generally used for applying nickel base alloys. For steel components, braze-welding, a variation of the normal oxy-acetylene process, is used. This is to avoid dilution of the coating by melting the substrate, since the addition of iron to STELLITE alloys results in a reduction in properties. |
A larger tip than for steel welding is combined with an increase in acetylene flow, resulting in a softer flame with a carburising feather about three times the length of the inner cone. The flame is played onto the surface, keeping the tip of the inner cone just clear of the surface. A small amount of carbon is absorbed into the surface, lowering its melting point and producing a watery, glazed appearance known as 'sweating'. A rod is introduced into the flame, and a small drop melted off onto the sweating area, where it spreads quickly and cleanly, in a similar fashion to a brazing alloy. |
Metal Inert Gas (MIG)
The MIG process is suitable for cobalt, nickel and iron base alloys. Carbide containing alloys can be deposited providing that care is taken not to generate dissolution of the carbides due to high arc energy.
The process lends itself to facing small components, allowing a high degree of precision to be achieved, and is easily automated.
The wires produced by DELORO STELLITE are available for spray transfer, pulse and dip transfer techniques. |
Submerged Arc Welding
The submerged arc technique is suitable for cobalt, nickel and iron base alloys, but is not normally used for alloys containing carbide, since the high energy arc causes dissolution of the carbides.
Using continuous wire, the process is ideal for large area coverage at hi surfacing speeds. Clean, porosity free surfaces are achieved at low cost, whilst multiple layers counteract the dilution effect. |
Manual Metal Arc (MMA)
The MMA process, using coated electrodes, is suitable for facing heavy sections of substrate and for carrying out simple repairs in situ. Surfacing is normally carried out using DC electrode positive (reverse polarity) but the process may also be carried out with AC, using a power source with a minimum open circuit voltage of 80V AC and a slightly increased welding current. The electric arc causes greater than normal dilution of the substrate, softening and toughening the first layer of deposit which is particularly advantageous for impact resistance in such items as shear blades. If the recommended procedure is followed there is only a small degree of dilution of the second layer. |
Powder Welding (PW) |
 Used for depositing nickel base and carbide containing alloys, it is also suitable for cobalt alloys, specially modified in powder form. The process is suitable for facing most steels, cost iron, nickel base and some copper base alloys.The powders used are applied at lower temperatures than rod, and the process is ideal for applications such as narrow beads or edge build up to provide small wear resistant areas, and for the surfacing of cast iron. The lower temperature results in slightly less scaling and distortion than with rod applications. |
Spray And Fuse (SF) |
 Spray and fuse is a two-stage process, the powder alloy being sprayed into position with a flame spray and then fused with an oxy-acetylene or similar torch, or in a vacuum furnace. The process uses specially modified cobalt and nickel base alloys and carbide containing grades of powders, depositing smooth, thin (I mm to 3mm) layers of STELLITE or DELORO alloys, metallurgically bonded to the substrate. |
Plasma Spraying |
 Plasma spraying is suitable for most cobalt, nickel and iron base alloys, plus a very wide range of ceramics, composites and carbides. The process may be used on most materials, which can be prepared by grit blasting. Deposits are thin (0.1mm to 0.2mm), high density (approaching 99% with the newer high energy plasma equipment), and since the substrate is only slightly heated, can be applied with a minimum of distortion. However, the coatings are not fusion welded overlays, and are only mechanically bonded to the substrate. |
Plasma Transferred Arc (PTA) |
 PTA is suitable for all cobalt and nickel base alloys, iron base and carbide containing grades, using specially formulated surfacing powders, and is suitable for most steel and nickel alloy substrates. This is a true welding process, deposits forming a metallurgical bond with the substrate. |
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