High-performance surface modification technology that contributes to extending the service life of dies (Patent number: 6015663)

“Minister of Education, Culture, Sports, Science and Technology Awards (MEXT Minister’s Award)”
Fumiaki Honda, Engineer, New Material Group, Processing Dept., Yasugi Works, Specialty Steel Business Unit, Proterial, Ltd.

Modifying a metal surface by coating it with a film is an effective technology for increasing the strength, durability, and sliding properties of dies and auto parts. When applied to a die, it can significantly extend the service life of the die.
In recent years, the load on dies has been increasing due to the growing strength of processed materials, including high-tensile steel sheet, increased processing accuracy, and the increasing speed of casting cycles. This has made surface modification even more important than before. Before this invention, however, galling^*1 would occur suddenly during surface modifications in some use conditions, reducing the service life of the die, which was an issue.

The inventor of this patent discovered that the sudden occurrence of galling in the tough usage environments of dies is attributable to a metallic powder from the die material and abrasion powder generated during sliding adhering to the die, and he studied method to prevent the powder from adhering and enable dies to have excellent sliding properties even after they have been used for a long time. As a result, he invented a surface modification with the optimal elemental composition and film structure, which can inhibit the occurrence of galling by making excellent sliding properties possible in a wide range of use environments, from cold to warm.
This surface modification creates a hard film on the surface of the die. The film consists of a laminated film composed of alternating layers of chromium nitride and vanadium nitride films (layer A), and a vanadium nitride film (layer B) that is applied over layer A. This hard film structure inhibits the local adhesion of the processed material and the jamming of abrasion powder, which causes galling damage, through the action of the low-melting oxide that is generated on the surface layer of the film in the die usage environment. It thus extends the service life of dies.

Proterial provides the proprietary Tribec™ high-functional surface modifications applying hybrid PVD^*2 technologies that the ensure high abrasion resistance, excellent lubricity, and heat resistance required of dies. This invention has been used practically as Tribec™ Kagari, one of the Tribec series of coatings, contributing greatly to extending the service life of dies.