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Hardfacing is a welding process used to apply a material with increased hardness, ductility, erosion-resistance, and/or corrosion-resistance relative to the base (parent) material. It is also commonly referred to as cladding or hardsurfacing. Due to hardfacing materials improved properties, a part’s service life is prolonged. Hardfacing can be applied to new part to offer a value-added feature, or it may also be applied to repair previously deteriorated parts.

The most popular procedures used to apply hardfacing are:

  1. Flux cored arc welding (FCAW)
  2. Open arc welding / gasless welding (OAW)
  3. Gas metal arc welding (GMAW)
  4. Shielded metal arc welding (SMAW)
  5. Submerged arc welding (SAW)
  6. Gas tungsten arc welding (GTAW)
  7. Oxyfuel or oxyacetylene welding (OFW)
  8. Thermal spraying

Flux Cored Arc Welding

FCAW is a semi-automatic or automatic arc welding process. This process typically requires a continuously-fed tubular electrode containing a flux (a chemical substance added to the welding environment as a cleaning agent, flowing agent, purifying agent or combination thereof) and a constant voltage. This welding process is often chosen in construction applications because it is quick and easily transportable.

Open Arc / Gasless Welding

OAW is a semi-automatic or automatic arc welding process. This process typically requires a continuously-fed tubular electrode that may or may not contain flux, and a constant voltage. This welding process is often chosen in field applications because it is quick, easily transportable, and requires no gas connection.

Gas Metal Arc Welding

 GMAW (sometimes called MIG -metal inert gas welding) is a semi-automatic or automatic welding process in which a consumable wire electrode and shielding gas are fed through a welding gun. A constant voltage is most commonly used with this process.

This process is chosen because it provides high quality welds that can be deposited much faster than with SMAW or TIG welding processes. It is also versatile in that it can be used with a wide range of alloys and operated in multiple ways.

It is passed over when the application requires mobile flexibility as it cannot be used in the vertical or overhead welding position.

Shielded Metal Arc Welding

SMAW is a manual arc welding process that uses a consumable electrode coated in flux.

flux coated electrodes

An electric current forms an electric arc between the electrode and the base metal. As the weld is laid, the flux coating disintegrates and forms a shielding gas and a layer of slag which protect the weld until it cools. This is a common method of welding as the process and equipment are relatively simple.

Submerged Arc Welding

SAW involves the formation of an arc between a continuously-fed wire electrode and a workpiece – similar to GMAW. This process uses a flux to create protective gases and slag to the weld pool. Before welding, a thin layer of flux powder is placed on the workpiece surface itself. The arc then moves along the line and excess flux is recycled via the flux feed hopper.

 

SAW is often chosen because of its high quality welds (often with little operator skill required), minimal fumes, and relatively high metal deposition rates.

A major disadvantage is that it can only be welded in flat or horizontal position.

Gas Tungsten Arc Welding

 GTAW (or TIG – tungsten inert gas welding) is a welding process that produces an arc between a non-consumable electrode and the workpiece. The weld is shielded by a shielding gas that forms around the weld area. GTAW can be performed manually or adapted to automatic equipment. This process is very versatile as it can be welded in all positions and with most metals. This process is commonly chosen for critical applications in the nuclear, chemical, and aerospace industries.

GTAW produces exceptionally high quality welds. The major drawback of this process is that deposition rates with manual welding are low.

Oxyfuel or Oxyacetylene Welding

 OFW is a group of welding processes that use heat with a fuel gas flame with or without the application of pressure and with or without the use of filler metal. OFW includes any welding operation that uses a fuel gas combined with oxygen as a heating medium.

Because of the control the welder has over the rate of heat input, and the temperature of the weld zone, it is well suited for the welding of thin sheet, tubes, and small diameter pipe.

Thermal Spraying

Thermal spraying is a coating process that consists of a heat source and a coating material in either powder or wire form that is melted and sprayed onto surfaces at high velocity. There are three major categories in the thermal spray processes family: Flame spray, electric arc spray, and plasma arc spray. There are several of sub-categories under each.

Thermal spray advantages include:

  • High throughput rates
  • Low heat input rates
  • Wide variety of materials can be used
  • Favorable economics
  • Easily repeatable process

 

If you have any questions regarding processes or applications, contact us and we will get you in touch with one of our technical experts.


When faced with a decision on what kind of hardfacing product to use, one of the first questions you should be asking is “what kind of wear am I up against?”. Keep in mind – you will often encounter more than one type of wear at a time.

While there are many types and combinations of types of wear. The most typical modes (and factors) encountered are:

  1. Abrasion
  2. Impact
  3. Adhesion/Galling
  4. Erosion
  5. Corrosion
  6. Heat
  7. Cavitation

What is abrasion?

Abrasion is the wearing away of a surface by means of friction – often grinding or scraping. Abrasion is the most common type of wear encountered, and can be broken up into three categories:

  1. Low stress abrasion – is when a metal surface is worn away by an abrasive media that polishes the surface, removing surface material. An example would be sand sliding across a surface at a low angle of attack.
  2. High stress abrasion – is when a metal surface is worn away by an abrasive media that polishes the surface, removing material. An example would be a grinding operation with forces high enough to crush minerals that are hard enough to scratch and cut the hardest materials.
  3. Gouging abrasion – is when a metal surface is worn away by conditions of high stress, usually caused by impact loading. An example would be a rock crushing application having a combination of high impact and abrasion.
Crushing large chunks of rock into smaller pieces which will be used for road bed on a new road construction project. Shallow dof with focus on gravel leaving conveyor belt.

Close up of rock crusher in action. A good example of gouging abrasion.

What is impact wear?

Impact wear is when a metal surface is worn away by forces high enough to cause metal to deform, leading to metal fatigue and cracking.

Bucket teeth and other ground engaging tools often see both impact and abrasion.

What is galling wear?

Galling wear is an extreme version of adhesion wear. It occurs when there is a transfer of material between sliding metallic surfaces – particularly when there is a lack of lubrication. An example of this would be a bearing surface with low or no lubricant on a steel mill processing roll.

  

What is erosive wear?

Erosive wear is when a surface is worn away by abrasive particles suspended in air or liquid. An example of this kind of wear is sand and water flowing through a pipe.

Slurry pipes are used to transport slurry (a mixture of ore concentrate and water) from a mineral processing plant after the ore has been processed.

What is corrosive wear?

Corrosive wear is the deterioration of metal as a result of a chemical reaction.

Salt mine in Poland

Heat – softens metal causing accelerated wear when combined with any of the above.

Cavitation – is vapor bubbles in a liquid collapsing under pressure that over time will fatigue and cause the metal surface to spall.

Determining the type of wear and the most suitable hardfacing can be challenging and may require trial and error. Feel free to contact one of our technical experts here at Polymet for assistance in selection.


Polymet’s New Address

June 5th, 2017

Please be sure to send all correspondence to our new address!

7397 Union Centre Blvd. 

West Chester, Ohio 45014


Polymet Celebrates 50th Anniversary

January 24th, 2017

 

anniversary-logo2017 marks Polymet’s 50th year in business. What started as a small manufacturing plant, has grown into an industry giant. Polymet is known for meticulously designing unique, high quality products for the worlds most critical wear problems.

Polymet has lot in store this year. The first quarter of 2017 we will be moving into a larger facility to house all processes and functions under one roof. We will be launching a new, more streamlined website as well as a more modern approach to the brand overall. Keep your eyes peeled for exciting news and promotions throughout the year.


valve-banner

 

 

Though not exhibiting this year, Polymet is very excited to be ramping up for the Valve World Americas Expo in Houston next week. “We are very excited to be able to meet with some of our existing customers and meet potential new customers” – Bob Unger, Polymet Sales Manager.

Polymet specializes in manufacturing nickel and cobalt based alloys in solid form. Their POLYSTEL brand consisting of cobalt 1, 6, 12, & 21 consumables has been used in the valve market for years and it is a focus area for the Polymet sales team this year. Polymet’s manufacturing capabilities and industry knowledge ensure that their wire is the highest quality.