Select-Arc Hardsurfacing Products
HARDSURFACING
Hardsurfacing encompasses a broad range of alloy compositions which are designed for a variety of applications. The basic concept is to deposit, by an arc welding process, an alloy onto a metallic component which resists wear more effectively than the base metal of the component. By doing so, you increase the component life. The hardsurfacing alloy may also be required to provide additional resistance to other conditions including impact, adhesion, corrosion, erosion or elevated temperatures. Reasons for Hardsurfacing
Metal components eventually wear out from use or break in service. Until the advent of buildup and hardsurface welding operations, the part was discarded and replaced with a new O.E.M. part. Initially, the idea was to reclaim the worn part by building up the worn area with welding and/or subsequent machining. This practice of reclaiming the worn component proved to be a significant cost savings over the purchase of a new component. Some time later, the concept of improving the life of a metal component by welding a more wear resistant alloy to the components surface evolved. Again, this proved to be a great value in reducing the cost of operation. Hardsurfacing does the following: 1. Reduces the cost of operation by reclaiming worn components at a fraction of the new O.E.M price. 2. Increases the life of components by utilizing more wear-resistant alloys. 3. Reduces machinery downtime by increasing component life. In conclusion, reclamation by the use of buildup and hardsurface welding reduces costs of operation, making you more competitive in your industry. Alloy, Hardness vs. Wear
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One common misconception is that higher hardness in the weld deposit yields better wearresistance. Greater hardness does not always equate to less wear and longer component life. Different alloys with similar hardness values can result in entirely differing wear-resistance properties. Typically, the volume density, or amount of carbide present in the alloy matrix, imparts the wear-resistant properties to the alloy deposit. Therefore, the greater the volume of carbide, the greater the wearresistance of the alloy. In some cases, the most wear-resistant alloy is not always the best solution for the application. As carbide volume increases, the more crack sensitive and less impact resistant the deposit becomes. The choice of which hardsurfacing alloy to use is normally a compromise between wearresistance and impact-resistance of the alloy for a given application.
Surfacing Alloy Groups
Hardsurfacing and buildup alloys are generally broken down into broad groups. Some groups can be broken down into smaller, more specific groups, but this is unnecessary for the majority of the market. Buildup Alloys
The buildup group is composed of lower carbon, low alloy steels, similar in range of chemistry to the component being reclaimed. By arc welding, the component is rebuilt to near original dimensions prior to final hardsurfacing operations. Typically, these alloys are machinable and offer a good combination of hardness and toughness. Consideration should be given to heat treating procedures when welding with these alloys to reduce residual stresses caused by the welding process, reducing the potential for cracking. Austenitic Alloys
Typically, austenitic steels exhibit very good toughness and strength under high impact conditions. As deposited, these alloys can be very ductile, yielding hardnesses in the range of 17 to 23 Rockwell C scale hardness (HRc). Under impact, the alloy microstructure deforms, or work hardens, resulting in a hard, tough surface layer. Hardness can be increased to a range of 44 to 54 HRc. Because of the initial ductility of the deposit, buildup depth is generally unlimited. Some of the austenitic group can be considered both buildup and hard-surfacing alloys due to their ability to be deposited as a very ductile alloy and then work harden in service. This work hardening property makes them an ideal choice for rebuilding manganese crusher parts where extreme impact with low abrasion is encountered. Martensitic Alloys
The martensitic group includes a wide variety of hardsurfacing and some buildup alloys. These alloys are generally considered a good choice for metal-to-metal wear-resistance. Weld deposits yield good impact and abrasion properties. These alloys are also termed “air hardenable” meaning that the cooling rate is directly related to final hardness. Faster cooling promotes formation of the martensitic structure. Care must be taken with regard to heat treatment procedures (preheat, interpass, postweld stress relief) to avoid residual stresses and cracking of the weld deposit. Carbide Containing Alloys
This group of alloys can include many different carbide forming elements either alone or in combination. Typically high in carbon content, the weld deposit is composed of single, primary
