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  1. Issues and Ideas

Tungsten Carbide Adds Strength, Wear-resistance to Sand Handling Equipment

Oct. 26, 2006
Sand binders may be the source of many problems for metalcasters, but one that has gotten fairly little attention is their effect on process equipment.

The wear-and-tear that organic sand binders inflict on sand-mixing equipment leads to significant maintenance and replacement cost.

Technogenia, a French company founded 27 years ago, offers a series of high-performance hardfacing products to various heavy industries to counteract equipment abrasion. “Hardfacing” refers to various processes whereby weld materials are applied to a substrate to improve on the original material’s condition or performance. These processes are typically used to improve wear — and corrosion-resistance to cutting edges. Among the common hardfacing techniques are arc welding and torch welding, among others.

Technogenia began producing fused tungsten-carbide in 1981, and has developed and updated the process since that time, and also developed new forms of the material to offer wear-resistance to different products and shapes. And, its Technocasting process is used to produce complex angular shapes.

At first, Technogenia produced fused tungsten-carbide in a high-temperature induction furnace, then later adopted a cold crucible process with electromagnetic levitation. Next, a “cold crucible” induction fusion system was introduced. In 1990, Technogenia began research on a carbide deposit process using laser technology. It continues to research deposition processes using laser technology.

For the sand-preparation and mold making equipment, Technogenia offers tungsten-carbide coatings and hardfacings. Tungsten-carbide adds material toughness that will withstand the corrosive effects of organic sand binders, such as soot or clay.

To prepare sand molds for iron or steel casting the sand is mixed with an organic binder, which means the mixer blades must be strong enough to execute the process thoroughly and still endure significant wear. Without hardfacing, a mixer blade may be functional for a month or so of typical operation before it needs to be replaced. The company claims its hardfacing products are used by several high-volume automotive foundries in Europe.

Technogenia’s tungsten-carbide powder Spherotene can be deposited on a blade’s surface, and impart anti-abrasion characteristics suitable for the parts that get prolonged exposure to the sand and binders. Spherotene powders are comprised of spherical particles of monocrystaline tungsten carbide that are particularly hard, 1,800 to 4,000 HV (Vickers hardness). The particles can be applied by a welded-on cast-nickel cord, thermal spray, special casting, or precision laser. Technogenia claims the hardfacing will extend a part’s service life by almost ten times what may be expected with a more traditional chrome-carbide hardfacing.

Technogenia’s hardfacing cords (Technodur and Technosphere) provide shock resistance as well as anti-abrasion protection. Both are flexible, nickel-core wire coated with Spherotene for wear-resistance. The compactness and “anti-abrasion, anti-erosion” charactaristics of the cords help strengthen the surfaces of scrapers, feeder heads, cutter blades, corner pieces, mold drills, etc.

Tungsten-carbide hardfacing forms a metallurgical bond with the base metal on a part — scrapers, feeder heads, cutter blades, corner pieces, mold drills, and so on. The two types of cord differ in carbide hardness, and are available in diameters ranging from 0.1 to 0.5 in. to be welded to parts with an oxy torch to achieve the desired degree of anti-abrasion and impact protection.