Influence of the structure of the composite: ‘nitrided layer/PVD coating’ on the durability of forging dies made of steel DIN-1.2367

The paper presents research results of the influence of the ‘nitrided layer/PVD coating’ composite structure on the durability of forging dies made of steel DIN-1.2367. Five structures of the composite with different PVD coating materials were investigated. The following types of PVD coatings were applied: TiN/Ti(C,N)gradient, (Ti,Cr)N, (CrN/TiN)×3, (Cr/CrN)×3, CrN. The investigated composites were created by means of the surface ‘duplex’ treatment method in a two-stage separable cycle. The nitriding process was executed with the use of the regulated gas nitriding method, whereas the PVD coatings were created by means of the arc-vacuum method. The paper presents results of materials investigations (metallographic analysis, X-ray diffraction phase analysis, adhesion scratch tests and thermal fatigue tests) as well as the results of laboratory forging tests executed in different conditions (two different temperatures of the forged material and two different temperatures of the die) for dies covered with each of the investigated composites. The wear intensity of the investigated dies was assessed by means of precise three-dimensional measurements while the wear mechanisms were investigated by optical microscopy. On the basis of the received results authors determined the influence of the composite structure and its material properties on the mechanisms and intensity of forging dies destruction.