Potential of Duplex Plasma Deposition Processes for the Improvement of Wear Resistance of Hot Forging Dies

Abstract

The efficiency offorging processes is significantly influenced by the tool and scrap costs whichin their turn depend on the life time of forging dies. The tools used for hotforging are subject to process-related high mechanical, tribological, chemicaland thermal-cyclic loads which usually interact with each other. In comparisonto other manufacturing methods, the resulting load spectrum leads to extensivewear and thus to the failure of forging dies after a short tool life. Toincrease the wear resistance of forging dies, duplex treatments consisting ofplasma nitriding and plasma deposition techniques were used to improve thesurface properties and hence to increase the die life time. By basicinvestigation of the wear mechanisms the potentials of newly developed vanadiumdoped chromium nitride and boron containing titanium nitride coating systemswere investigated. Within the presented work it is demonstrated that vanadium-dopedchromium nitride layers have a high wear reduction potential for hot forgingdies.

Adapted surface properties of hot forging tools using plasma technology for an effective wear reduction

“…On the left side a contoured forging die with a global treatment and on the right side an industrial forging die for turbine blades with a global and a local treatment are shown. These results show the necessity and the high potential of appropriate partially and load dependent treatments and coatings [8].…”

“…The untreated tool surfaces showed a gradual increase of the friction factor by every increase of the structure intensity, while the duplex treated tool surfaces showed a sudden increase by applying any of the structure intensities on the same level. An explanation for this behavior can be given by taking the influence of the nitriding and coating process on the friction conditions into account [8]. While an influence of the structure can clearly be verified, it is overlapped by the influence of the duplex treatment.…”

“…Former work [8] showed that high thermal loads lead to softening processes in the near-surface zone of the tool promoting other wear mechanisms like abrasion and plastic deformation. A large nitriding hardness depth was identified to be an appropriate wear protection method.…”

“…The design of the thermally loaded die considers the fact that the soft convex radius leads to high thermal accumulation as it has been identified for the center cone region of the contoured forging die [8]. Two different mechanisms depending on the thermal impact need to be respected.…”

Deposition welding of hot forging dies using nanoparticle reinforced weld metal

“…Tribological charges and surface crack formation lead to the necessity of hard and wear-resistant layers. The use of thin layers applied by chemical or physical vapour deposition (CVD/PVD) can fulfil these requirements [10].…”