10. Coatings for Forming Dies of Advanced High-Strength Steel

Recently, most of the automobile companies and related industry increased their efforts in further increasing the safety and in reducing the weight of car body and chassis parts by using advanced high-strength steel sheets. Traditional hard coatings used in forming dies cannot fulfill the required wear resistance and durability. The coatings for the 980 MPa class forming dies need to have complex material performance like wear, temperature, and fatigue resistance as well as low-friction behavior. In order to develop the newer and higher-performance coatings for such forming operations, the ideas of carbon doping or carbon overlay coating should be considered for low-friction behavior in current dies. Furthermore, toughness, fatigue resistance, and strong bonding properties should be further improved through nitriding and followed up with multilayers of CrN, TiN, etc. In this work, TiAlCrCN and AlTiCrN + CN showed high promise among 18 coatings considered, and these should be considered for use on future drawing dies. Ultimately, the enhanced coatings or layer design with much refined nanograins and nanolayers can be developed for applications requiring the forming of much higher-strength steels (i.e., ultrahigh-strength steels or 3rd generation AHSS sheets) and of more complicated shapes.