Hardfacing (Surface hardening overlay welding method) is a technology, by using various kinds of methods, to produce a hardening layer on the metal surface in order to extend the lifetime of parts. For the methods, there are Gas Welding, Arc Welding, and Thermal Splaying etc.
As a pioneer of Hardfacing, we are servicing various kinds of Welding methods and Thermal Splaying methods, and our technology has been acquiring favorable reputations by our customers over a half-century.
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- Hardfacing Overlay Welding
- (1) Gas Welding
- Oxy-Acetylene Gas Welding
- Arc Welding
- Thermal Spraying
01.Gas Welding
Gas Welding is, by making use of high temperature burning heat generated
by chemical combination of flammable gas and oxygen, to melt a part of welding rod and weld.
As gas-heating area is wide, it produces less cracking, and is mainly applied to cobalt-base and nickel-base hardfacing alloy.
Compared with other welding methods, weld penetration to base metal is much less, and considerable alloy hardness is available from the 1st layer. Gas welding is a manpower method and matured technical skill is necessary.
02.Shielded Metal Arc Welding
By imposing voltage onto welding rod and base metal, arc is generated, and this arc heat melts the electrode and the base metal to weld them.
Heat input influence to base metal can be controlled by welding rod diameter, current and/or voltage. However as the weld amount is small, this method is not suitable for large amount of welding.
Many kinds of welding consumables are available for this method, like as copper alloys, cast iron base, steel base, stainless steel, cobalt-base alloy, nickel-base alloy etc.
03.CO2 Gas Arc Welding, MAG Welding
Arc is generated between weld wire and base metal, and this arc heat melts the wire and the base metal to weld them.
At that time, to prevent bad influence from the atmosphere, CO2 gas or argon gas is used as shielded gas. Compared with other welding methods, welding speed is higher and operation is easier, so high effective overlay is possible.
This method is applicable to small or large size objects, and is also used for full automatic welding using robot.
Just like Shielded Metal Arc Welding, many kinds of welding consumables are available for this method, like as copper alloys, cast iron base, steel base, stainless steel, cobalt-base alloy, nickel-base alloy etc.
04.TIG Welding
By TIG Welding, arc is generated between tungsten electrode and base metal in argon gas atmosphere, and this arc heat melts the welding rod and base metal to weld them. Compared with CO2 Welding and MAG Welding, welding speed is lower.
Depending on the welding condition, weld heat input can be controlled, that means weld penetration can be controlled, therefore, deformation at welding can be minimized.
Many kinds of welding consumables are available for this method, like as cobalt-base alloy, nickel-base alloy, stainless base, iron base etc., and by the selection of wire diameter, overlay with lower heat input is possible.
05.Self-shielded Arc Welding (Open Arc Welding)
Self-shielded Arc Welding is a welding method that uses flux cored wire, and doesn’t use shielded gas.
Flux contains gas-generating agent, deoxidizing agent and slug-forming agent etc., and the generated gas prevents the atmosphere’s (air’s) penetration, and the deoxidizing agent prevents bad effect by oxygen that penetrates from the atmosphere.
This welding method doesn’t use shielded gas, and is therefore suitable for on-site and/or outdoor welding work.
For welding consumables, mild steel, high magnum iron base, high chrome iron base are available.
06.Submerged Arc Welding
By Submerged Arc Welding, arc is generated between weld wire and base metal in welding flux, and this arc heat melts the weld flux and weld wire to weld them.
Because large current welding is possible, welding speed is high, and by making use of multi-electrode, the operation can be highly efficient.
This method is applied to overlaying mainly for rolls and rollers etc. For welding consumables, mild steel, high magnum steel, hot work tool steel, high speed steel, high chromium iron etc. are available.
07.Band Electrode Overlay Welding
Band Electrode Overlay Welding is high current welding method. Just like Submerged Arc Welding, arc is generated between welding consumables and base metal in welding flux, and deposition is performed.
While Submerged Arc Welding uses welding wire, this method uses band steel, and therefore deposition rate and efficiency are higher.
Mainly used for overlaying of large-scale parts like as steel mill rolls, guide rollers etc. Welding consumables are limited to stainless steel, chrome molybdenum steel, mild steel etc., because band steel is used.
Therefore, to satisfy the component of metal deposit, welding is performed by the method that chemical component is taken-in from welding flux during melting time.
08.PTA Overlay Welding
PTA Overlay Welding is to heat the gas by generating arc inside torch with using high frequency generator. Powder welding consumables are supplied into a gas stream, which was ionized by the ultra high temperature, and deposition is performed.
Mixed gas like as nitrogen, helium, argon etc. are used for this method.
Overlaying thickness is 3-4mm for one layer, and higher efficient overlaying than the other methods is possible. Also, as weld penetration is shallow and dilution of deposition component is low, mechanical property of consumables can be obtained by one layer overlay.
For welding consumables, stainless base, cobalt base alloy, nickel base alloy, high-speed steel, cermet etc. are available.
09.Powder Flame Splaying (Self-fluxing Alloy Splaying)
Using oxygen and acetylene flame as heat source, thermal splaying is performed with the melted consumables.
Self-fluxing alloy (alloy of nickel and cobalt base adding silicon) is used
during splaying, and after the splaying, fusing treatment is performed.
Because fusing treatment deletes blowholes and forms alloy layer, bonding strength near to welding is available.
10.High Velocity Oxy Fuel gas Flame Splaying
By raising the pressure of combustion chamber, high-speed gas flame is generated. Splaying powder is supplied into the chamber so that they hit the substrate at high-speed to form splay deposit.
Because high-speed flame by high-pressure combustion is given, higher density and higher bonding strength splay deposit than other splaying methods can be formed. This method is used mainly for the splaying on tungsten carbide base.
11.Plasma Splaying
By flowing inert gas in between electrodes and electrify them, very high-temperature plasma jet is formed. Splaying powder is supplied into the plasma jet, and by accelerating the powder while melting it, splaying deposit is formed. As the plasma jet becomes high temperature over 10,000℃, it is suitable to perform splaying on material with high melting point like as ceramic.
Also, substrate’s temperature at splaying can be controlled about 150℃, therefore performance with almost no distortion by heat is possible.
12.Rokide Splaying
Splaying consumables sintered as rod shape are supplied into compressed air with oxygen - acetylene flame as heat source, and splaying is performed. Splay melting temperature is 2,500～3,000℃, and completely melted consumables are splayed.
Therefore, very precise splaying deposit can be formed.
Mainly used for ceramic base thermal splaying