Hybrid gas phase Ti-B-C-N coatings doped with Al

Abstract

Deposition of Multicomponent hard coatings (Ti-B-C-N) on the molybdenum high-speed tool steels (AISI M52) has been achieved by mixed vapor deposition technique to improve the mechanical properties of the surface. The Ti-B-C-N coating samples were produced by a hybrid gas phase process, were in this technique, the coating materials that supplied in the gas phase were produced from powders that vaporized by thermal energy (that is, PVD- Reactive Evaporation Process), while the reactor that used to deposit Ti-Base coatings is a hot-wall chemical vapor deposition (HWCVD) system equipment. The resulting coating exhibit different amounts of the Titanium oxide phase, which is characterized by the low mechanical and thermal properties. These phases (Ti-O) will have determinant effect on the coated high speed steel tools. The alloying of transition metal nitrides and borides (TiN, BN, and TiB) with stable oxide-forming elements (for example, Cr, Al, Si and Ni) will have the effect of decreasing crystallinity, promoting nanocrystalline structure and increasing oxidation resistance. Ti-Base hard film was characterized by XRD technique, and Scanning Electron Microscopy (SEM). Mechanical characterization of the hard films has been performed by using The Ball-on-disk wear tests. With different deposition temperatures (550–950 °C) and at the same reactive gas flow rate 2.5SLPM (Standard Litter Per Minute), Al doping in the Ti-B-C-N coating has proven a great success by producing a new film microstructure (free of Ti-O phases) which contains fine fiber structure as a strengthening second phase in the Ti-B type structure with a sufficient amorphous phase (B-N) as a matrix. Maximum hardness of 4230 HV is achieved, with better thermal stability during the process of the wear test than the uncoated H.S.S samples. Also a great enhancement in the wear resistance values for this coating film (Volume loss = 1.8291*10−7 mm3) was reported.