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July 6th, 2011

DLC coatings reduce plowshare friction in soil

Published on July 6th, 2011 | By: Eileen De Guire

 

DLC coated plowshare (right). Left images show difference between initial test (top) and test of DLC coated tool. Credit: Felizitas Gemetz; Fraunhofer IWM/Martin Höerner; Fraunhofer IWM.

The humble plowshare may be the next beneficiary of sophisticated surface engineering using diamond-like carbon. Researchers from the Fraunhofer Institute for Mechanics of Materials IWM, working with RemBob partners, have found that friction between the blade and soil is reduced by half for DLC-coated plowshares, which reduced the required tractor power by more than 30 percent in some tests.

According a Fraunhofer press release, German farmers use nearly a billion liters (about 265 million gallons) of fuel per year to work the soil, and it is estimated that about 50 percent of the energy used during plowing or harrowing is sacrificed to friction between the plowshare and the soil.

Smooth-cutting plowshares mean tractors can be smaller and lighter, which is good for fuel economy, but also prevents soil compaction by the large machines. Fraunhofer physicist and fruit farmer, Martin Hörner says in the press release, “From the environmental point of view it would be better for tractors to be smaller.” When soils are loose, less power is need for tilling. Looser soils are healthier, too, because nature’s soil enrichers—worms and other creatures that turn soil and add nutrients—are able to maneuver. Looser soils absorb moisture better, too.

If saving time is the priority, farmers could opt for machines that are wider and cultivate more area with each pass.

In addition to reducing friction, DLC coatings provide corrosion and wear resistance to the high-durability steels that are used for plowshares. According to Fraunhofer’s Hörner, wear can reduce the mass of a tine on a circular harrow by about half during the course of a growing season. Abrasive soil, sand and stones wear down conventional coatings quickly, and DLC coatings are able to withstand the extreme stresses and strains better than conventional coatings.

However, the steels used are proving to be poor substrates because they deform too easily, and the rigid DLC coatings tend to spall. Alternative plowshare materials being investigated by the research team include nitrided steels, glass fiber reinforced plastics and tungsten carbide.

(In a related story, last year we wrote about a German company that is marketing razor and surgical blades made of carbide coated with DLC nanoparticles that company says are so tough that they keep their edge for five years.)

The Fraunhofer group’s next step in its research is to find a substrate–DLC combination that will allow a plowshare to cover 20 kilometers without a coating failure.

Less time, less fuel, less maintenance adds up to more food and less cost to produce it.


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