Every part involved in the rigors of farming is exposed to destructive wear. Farmers, manufacturers and machinery dealers are finding benefits through advanced hardfacing methods that reduce costs, prolong equipment life, eliminate downtime and reduce unnecessary parts inventories.
Troy Feuss, Global Hardfacing Manager of Cleveland-based Postle Industries, provided practical information on hardfacing during a digital demonstration, helping farmers and manufacturers select the application most appropriate for their ag equipment.
In the digital demonstration, Feuss covers the following frequently asked questions about hardfacing products and more.
What is hardfacing?
Metal parts often fail their intended use not because they fracture, but because they wear by abrasion, impact, metal-to-metal contact, or some other form of wear, which causes them to lose dimension and functionality. Hardfacing, also known as hard surfacing, is the application of a build-up or wear-resistant weld metal onto a part's surface by means of welding to extend the life of the part. The weld metal may be applied as a solid surface or in a pattern, such as a waffle pattern, herringbone, or dot pattern, etc.
Hardfacing is becoming increasingly important for many industries to protect equipment that is exposed to wear and abrasion. Postle Industries produces products used in mining, dredging, recycling, farming, railroads, earthmoving and construction, cement, logging, power generation, oil and gas drilling, as well as steel making and forging. Extending the life of wear parts will save thousands of dollars and improve productivity. Hardfacing can be used to recondition parts that have already been exposed to wear and have lost their useful life or used in the manufacture of new parts to improve their life before they are put into service.
There are three main types of hardfacing applications:
- Build-up or Rebuilding
- Hardfacing or Overlay
- A Combination of Build-up and Overlay
What base metals can be hardfaced?
Carbon and low-alloy steels with carbon contents of less than 1% can be hardfaced. Medium carbon and low-alloy steels are very common since they provide higher strength than mild steels and better abrasion resistance. High carbon alloys may require a special buffer layer.
The following base metals can be hardfaced:
- Stainless steels
- Manganese steels
- Carbon and alloy steels
- Cast irons
- Nickel-base alloys
- Copper-base alloys
Carbon and low-alloy steels are strongly magnetic and can easily be distinguished from austenitic manganese steel which is non-magnetic. There are many low-alloy and higher carbon steels that are used for manufacturing equipment and spare parts, especially equipment that requires higher strength and abrasion resistance. They are not easily differentiated but should be identified to determine proper preheat and post-heat temperature. As the alloy content increases, the need for preheat and post-heat becomes more critical.
For example, steel made from 4130 generally requires a preheat of 400ºF(200ºC). Steel used for rails is typically higher carbon and requires a minimum preheat of 600ºF to 700ºF (315ºC to 370ºC). Manganese steel does not require preheat. In fact, steps should be taken to keep the base metal heat below 500ºF (260ºC).
What are the most popular welding processes used to apply hardfacing?
In order of popularity, the following welding processes are used:
- Flux cored arc welding (FCAW) with open-arc or gas-shielded hardfacing wire
- Gas metal arc welding (GMAW) with gas-shielded wire
- Shielded metal arc welding (SMAW)
- Submerged arc welding (SAW)
- Gas tungsten arc welding (GTAW)
- Oxy-fuel welding (OFW) or oxyacetylene welding
- Plasma transferred arc welding, laser welding, thermal spray, and spray and fuse
There is a wide variety of equipment and power sources on the market. The current trend is toward the use of semi-automatic and automatic welding processes using FCAW and GMAW, which are about the same in terms of popularity. GMAW using either a solid wire or metal-cored welding wire must be used with a gas shield, whereas FCAW employs welding wires that are used open-arc or gasless, as well as with a gas shield. Shielded metal arc welding with flux- coated electrodes is still very popular, especially for field on-site hardfacing applications – equipment is inexpensive and portable.
Factors to be considered when selecting a suitable welding process:
- Welding equipment availability, including size of power source
- Weld with stick electrode or semi-automatic wire
- Availability of hardfacing consumables
- Size of welding consumable
- Gas-shielded wire, open-arc wire, or submerged arc wire
- Operator skill available
- Welding location – indoors or outdoors
- Component size, shape, and the area to be hardfaced
- Thickness of deposit
- Deposition rate
- Welding position – can the component be moved for welding in the flat position
- Machining requirements if any
- Desired finish (sub arc quality?)
- Component preparation for previously hardfaced parts
- Preheat and post welding treatments (temper/slow cool/air cool)
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