Metallurgical Breakthrough Eliminates Bushing Turns
SC-2, a new alloy coating for dozer undercarriages from John Deere, provides the best combination of hardness, toughness, wear resistance and corrosion resistance properties of any coating on the market. In fact, SC-2 is so durable that an undercarriage featuring SC-2 coated bushings does not need bushing turns to hold up over the long term.
SC-2 coated bushings are compatible with existing John Deere undercarriage designs, and will fit many other brands of dozers, as well, according to Tim Wodrich, undercarriage engineering supervisor. "The new SC-2 metallurgy is a giant step forward in the field of undercarriage design it delivers twice the wear life over standard bushings," said Mr. Wodrich. "SC-2 will take a huge bite out of downtime, now that turning bushings is no longer necessary."
The John Deere SC-2 Extended-Life Undercarriage features coated bushings that are the result of a patented process called Gopalite developed by John Deere senior staff metallurgist Dr. Gopal Revankar. The process produces a water-based slurry from a heavy alloy-metal powder and several organic additives. The slurry formula suspends the alloy powder and is used to apply the coating to the part surface, producing a coating that is uniform in both thickness and consistency. The ingredients and techniques used greatly reduce the slurry coating's susceptibility to breaking when subjected to high impact.
"Our new process uses a much higher temperature than is typical, along with special atmospheres. This gives parts superior wear characteristics compared to chrome plating and, like chrome plating, SC-2 is corrosion resistant," said Dr. Revankar. "The process also is much more environmentally friendly than chrome plating it does not emit all the caustic carcinogenic vapors that the EPA frowns on."
Intensive laboratory tests prove conclusively that SC-2 coating is 25% harder than chrome plating, according to Dr. Gopal Revankar. SC-2 coated steel held up four times better than parts not protected by SC-2 in a sand abrasion test. A brutal impact test also was performed in which a 220 lbs weight was dropped 500 times on an SC-2 coated bushing from a height of 30 in. and the coating remained undamaged. In another lab test, an SC-2 coated bushing was fractured in a hydraulic press and the coating stayed fused to the steel.
The coating also has been tested in the field for the past three years, running on dozers that work year-round with high-impact loads in extremely abrasive soil conditions, including fine sand. Each dozer had one chain with SC-2 coated bushings, and the other chain was equipped with normal production bushings.
"In each dozer, the SC-2 coated bushings showed more than 100% improvement in wear life over the production bushings," said Tim Wodrich. "This coating can take the severest pounding an undercarriage application can dish out."
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