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Increasing the efficiency of forging operations using adjusted tribological surfaces enhanced by hard coatings

: Behrens, B.-A.; Bouguecha, A.; Husic, A.; Baumer, M.; Paschke, H.; Lippold, L.


Tribology online 11 (2016), No.2, pp.432-443
ISSN: 1881-2198
Journal Article
Fraunhofer IST ()
tribology; hot forging; die surface; wear; nitriding; PECVD; surface structuring

Tools used in hot forging operations are subjected to high wear during processing due to complex load conditions with high temperatures and mechanical loads. The resulting abridged service lifetime of the dies highly restricts the cost-effectiveness of the production process. Several investigations indicate that the condition of the tool topography during several forging cycles affects the formation of wear distinctly. Thus, an enhancement of the topography in order to reduce tribologically caused wear is expected to increase wear resistance. Within this investigation an appropriate surface structure of forging dies is to be defined. For this purpose, efficient production methods like turning, milling and blasting are applied to generate distinguished die surfaces concerning topographical structures. By investigating the worn-out surfaces, the optimal surface structure can be determined, taking into account topography parameters deduced from the Abbott-Firestone graph. A mechanical stabilization of the created topography is necessary due to the high mechanical and thermal loads during hot forging leading to distinctive topography alterations. Thus, plasma duplex treatments were carried out, consisting of plasma nitriding and hard coatings produced by PECVD coating technique. It can be shown, that the created topography of the forging dies is sustainable over high amounts of forging cycles and thus leads to a reduction of wear.