15-01-2014, 03:39 PM
Advanced Manufacturing Processes
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Cladding:
Cladding is the bonding together of dissimilar metals. It is different from
fusion welding or gluing as a method to fasten the metals together. Cladding is often achieved
by extruding two metals through a die as well as pressing or rolling sheets together under
high pressure.
Laser Cladding:
Laser cladding is a method of depositing material by which a powdered or wire feedstock
material is melted and consolidated by use of a laser in order to coat part of a substrate or
fabricate a near-net shape part.
Process:
The powder used in laser cladding is normally of a metallic nature, and is injected into the
system by either coaxial or lateral nozzles. The interaction of the metallic powder stream and the
laser causes melting to occur, and is known as the melt pool. This is deposited onto a substrate;
moving the substrate allows the melt pool to solidify and thus produces a track of solid metal.
This is the most common technique, however some processes involve moving the laser/nozzle
assembly over a stationary substrate to produce solidified tracks. The motion of the substrate is
guided by a CAD system which interpolates solid objects into a set of tracks, thus producing the
desired part at the end of the trajectory.
Laser Beam Welding :
Laser beam welding (LBW) is a welding technique used to join multiple pieces of metal
through the use of a laser. The beam provides a concentrated heat source, allowing for narrow,
deep welds and high welding rates.
In general cases heat is required to fuse the metals for any types of welding, in laser beam
welding process the heat is obtained from the application of a concentrated coherent light beam
which striking upon the weld metal and melt the metal, such this weld joint is obtained,
this welding process is called laser welding. In laser beam, the lights are coherent, i.e. light rays
are identical and parallel. The laser device generates the concentrating light wave narrowly and
gets the highly intense beam which can imparts tremendous amount of heat energy on a small
area, this heat energy can fuse the metals, which is used for welding purpose.
Under Water Welding :
Underwater welding can be classified as :
1) Wet Welding
2) Dry Welding
In wet welding the welding is performed underwater, directly exposed to the wet
environment. In dry welding, a dry chamber is created near the area to be welded and the
welder does the job by staying inside the chamber.
Wet Welding :
The work to be welded is connected to one side of an electric circuit, and a metal electrode to the
other side. These two parts of the circuit are brought together, and then separated slightly. The
electric current jumps the gap and causes a sustained spark (arc), which melts the bare metal,
forming a weld pool. At the same time, the tip of electrode melts, and metal droplets are
projected into the weld pool. During this operation, the flux covering the electrode melts to
provide a shielding gas, which is used to stabilize the arc column and shield the transfer metal.
The arc burns in a cavity formed inside the flux covering, which is designed to burn slower than
the metal barrel of the electrode.