Surface Modification of Hot-Work Tool Steel Using Hybrid Treatment Techniques

摘要

The use of Physical Vapour Deposition (PVD) methods for modification of metal and alloys widens the capabilities of improving their physical and mechanical properties. In recent years, and in view of developing novel materials, hybrid processing techniques have been widely used. These techniques include an additional double or triple treatment, such as Electron Beam Hardening (EBH)+PVD; Plasma Nitriding (PN)+PVD; EBH+PN+PVD. In the work reported here we combined three technologies for surface modification of hot-work tool steel, namely, EBH+PN+PVD. W320 steel was used as a substrate material in a previously heat-treated (hardened and tempered) state. The EBH was carried out in Leybold Heraus W300-15/60 electron-beam equipment. The plasma nitriding was performed under the following process parameters: T_N = 620℃; t_N = 24 h; processing gas composition - 70%N_2+30%H_2. The PVD coating - a CrN layer - was formed by direct current reactive magnetron sputtering in a rotating magnetron system. The resulting films were studied as follows: (ⅰ) adhesion by using the Rockwell-C impact test to evaluate the adhesion strength HF; (ⅱ) micro-hardness HV and modulus of elasticity E; (ⅲ) composition by X-ray diffractometry (XRD).