— Reprinted with permission from Modern Application News, December 1996.
Photo shows the stages of the TD process from post-salt bath immersion, before cleaning and buffing, to the finished tool.
Shown are typical tools that have been treated with the TD process.
Galling was becoming so severe for two John Deere operations that some dies needed polishing after every run.
John Deere Horicon Works in Horicon, WI produces sheet metal stampings for lawn and garden products, using hot- and cold rolled steel to manufacture a variety of parts. In an attempt to solve problems with galling in severe applications the company had several form dies, broach punches and blank dies treated with Thermal Diffusion™ (TD).
TD is a surface modification process that improves performance and extends the life of tooling. It involves immersing tools in a fused borax salt bath at temperatures from 1,600°F to 1,900°F. Atoms of vanadium dispersed in the salt bath combine with carbon atoms in the tooling substrate to form a 0.0001" to 0.0008" thick vanadium carbide layer. This dense layer is extremely hard (3,200 to 3,800 on the Vickers scale) and peel resistant.
According to Randy Leider, process engineer at John Deere Horicon Works, “The TD process has outperformed anything else we have tried. We treated some of the dies over three years ago. They are still running parts without having to be polished and we have not lost accuracy yet.” He also noted that using TD makes parts clean up easier. “After we started using TD, we were able to change from heavy lubes to a light, water-soluble lube. The lighter lube is easier to clean off in our wash system.”
Lower Production Costs and Less Downtime
In their other operation, John Deere Harvester Works, the company was having similar problems in manufacturing farm equipment. During stamping, details on the tooling wore out quickly and the tools had to be pulled for maintenance. After treating the form tooling with TD, the treated dies lasted twice as long as the untreated dies, as reported by John Beardsley, John Deere Harvester Works contract administrator.
Cosmetics of the end product have also improved, according to Beardsley. “The maintenance of die having treated inserts has been greatly reduced since we started using TD Lube used in forming and drawing operations, and tooling replacement have also been reduced. TD coating is superior.”
In many other situations TD has been effective in extending tool life by five to 50 times over the life of untreated tooling. Air-hardening cold and hot-working die steels, like A2, D2, H13, high-speed steels and powdered particle high-performance steels that have a 0.3% or greater carbon content, work best for TD treatment.