Laser cladding

Vs.

Other Metal coating

technologies

HVOF

• High-velocity oxy-fuel (HVOF) coating is a thermal spray technique used to deposit protective coatings on a substrate.

• A blend of fuel (gaseous or liquid) and oxygen is injected into a torch and burned. The combustion products flow through a nozzle that accelerates the flow to a speed up to 1500 m/s. A powder feed stock is injected into the gas stream, which accelerates the powder up to 800 m/s. The stream of hot gas and powder is directed towards the surface to be coated. The powder partially melts in the stream, and deposits upon the substrate. The resulting coating has low porosity as and a high bond strength.

• HVOF coatings may be as thick as 12mm (1/2"). It is typically used to deposit wear and corrosion resistant coatings on materials. Ceramic and metallic powders can be deposited using HVOF. Common powders include WC-Co, Chromium carbide, MCrAlY, and alumina.

TIG Welding• Gas tungsten arc welding (GTAW), also known as tungsten inert gas (TIG) welding,

is an arc welding process that uses a nonconsumable tungsten electrode to produce the weld. The weld area is protected from atmospheric contamination by a shielding gas (usually an inert gas such as argon), and a filler metal is normally used, though some welds, known as autogenous welds, do not require it. A constant-current welding power supply produces energy which is conducted across the arc through a column of highly ionized gas and metal vapors known as a plasma.

• GTAW is most commonly used to weld thin sections of stainless steel and light metals such as aluminum, magnesium, and copper alloys. The process grants the operator greater control over the weld than competing procedures such as shielded metal arc welding and gas metal arc welding, allowing for stronger, higher quality welds. However, GTAW is comparatively more complex and difficult to master, and furthermore, it is significantly slower than most other welding techniques. A related process, plasma arc welding, uses a slightly different welding torch to create a more focused welding arc and as a result is often automated.

MIG Welding• Gas metal arc welding (GMAW), sometimes referred to by its subtypes metal inert

gas (MIG) welding or metal active gas (MAG) welding, is a semi-automatic orautomatic arc welding process in which a continuous and consumable wire electrodeand a shielding gas are fed through a welding gun. A constant voltage, direct currentpower source is most commonly used with GMAW, but constant current systems, aswell as alternating current, can be used. There are four primary methods of metaltransfer in GMAW, called globular, short-circuiting, spray, and pulsed-spray, each ofwhich has distinct properties and corresponding advantages and limitations.

• Originally developed for welding aluminium and other non-ferrous materials in the1940s, GMAW was soon applied to steels because it allowed for lower welding timecompared to other welding processes. The cost of inert gas limited its use in steelsuntil several years later, when the use of semi-inert gases such as carbon dioxidebecame common. Further developments during the 1950s and 1960s gave theprocess more versatility and as a result, it became a highly used industrial process.Today, GMAW is the most common industrial welding process, preferred for itsversatility, speed and the relative ease of adapting the process to robotic automation.The automobile industry in particular uses GMAW welding almost exclusively. Unlikewelding processes that do not employ a shielding gas, such as shielded metal arcwelding, it is rarely used outdoors or in other areas of air volatility. A related process,flux cored arc welding, often does not utilize a shielding gas, instead employing ahollow electrode wire that is filled with flux on the inside.

PTA Cladding• Plasma Transferred Arc Process (PTA Process) is used to fuse a metallic coating to a substrate in order to improve its resistance against

wear and/or corrosion.This technique is called hardfacing, wear surfacing, or more commonly wearfacing.

• During the process, metal powder is fed into a molten weld puddle (fusion bath) generated by the plasma arc at high temperature (up to 20,000 °C).All welding parameters, including powder feed, power input, plasma gas and shielding gas, as well as torch and work piece movement are automatized and computer controlled in PLASMA TEAM equipment.

• PTA hardfacing is a true welding process, with a metallic bond between the substrate and deposit.

• Deposit thickness can range from 0.6 to 6.0 mm, width from 3 to 10 mm when using a single pass; multipass welding reaches deposit thickness up 20 mm and width over 30 mm.

• The core of PTA process is PLASMA. The plasma (a gas sufficiently ionized to be electrically conductive) can be viewed as the natural state of matter (the so called fourth state of matter), with the other states existing only as variants to the normal.Plasma state constitutes more than 99.9% of all matter in the universe. Thermal plasma describes a gas which is at least 1% ionized, with a temperature greater than 13,000 °C, and is a good electrical conductor.

• In PTA hardfacing, two DC power supplies are used to first establish a non-transferred arc (pilot arc) between the tungsten electrode (-) and the anodic nozzle (+) and then a transferred arc between the tungsten electrode (-) and the work piece (+). The pilot arc is struck by a High Frequency device and the plasma gas flowing around the cathode is ionized at the electrode tip.

• When the transferred arc is ignited, the work piece becomes part of the electrical circuit and the plasma arc is directed and focused through the torch orifice into the work piece.

• Powder is metered, under a positive pressure of Argon flow, from the bottom of the torch into a pool of molten metal on the workpiece surface.

• The torch is then either moved by a side-beam carriage over the work piece, or the work piece is rotated or moved under the torch to produce a weld overlay deposit.

• The plasma arc deposit is fully dense and metallurgically bonded to the work piece. The deposit microstructure is dense, with formation of dendrites during solidification.

• One of the most important features of the PTA process is the control of dilution. PTA produces dilution as low as 5%, compared to 20-25% typically obtained when hardfacing by MGAW (MIG) and GTAW (TIG) processes. So it is possible to maintain the noble properties of deposit even in one single pass.

Plating processes

• Chrome Plating

• Nickel plating

• Zinc plating

• Galvanizing

• Titanium coating

• etc

Questions?