CHROME PLATING OF PRESS TOOLING USED IN THE PRODUCTION OF NEW ELASTOMERIC MATERIALS

Abstract

This research has produced multicomponent titanium-doped chromium coatings to strengthen the working surfaces of press tooling dies operated under aggressive conditions during the vulcanization of products from new elastomeric materials. The pressing was carried out on a hydraulic vulcanization press 100-400 2E. with plate sizes 400x400 of new elastomeric materials based on 10 wt.% carbonized fiber from PAN (RC Helper) or (USA), which significantly increases the heat capacity of rubber based on a copolymer of vinyl develfluoride and hexopropylene by 15-30% in the operating temperature range from 323 to 348 K. In the work, samples from mass-produced steels such as steel 20, steel 45, U8, 40H, and 40H16M were used for coating. Mixtures of powders with a dispersion of 60-250 microns of the following materials were used as reaction agents. In determining the required dispersion of reagents, we were guided by studies that found that the maximum completeness of the transformation is observed when using a reaction mixture with a fraction of 100-120 microns. The protective coatings on samples under the conditions of the SHS were obtained at the developed pilot plant DSTU12, consisting of the following main functional systems: reaction equipment; system for monitoring and controlling technological parameters; and gas utilization system. The organization of the SIS consists in creating a powder mixture and an environment that provides exothermic interaction at the local initiation of the process (ignition). Then, the reaction wave propagates spontaneously (combustion) and the synthesized product is cooled. According to the type of chemical reaction, three SWS processes can be distinguished: direct synthesis from elements; direct synthesis from compounds and exchange reactions; and metallothermal SHS (reactions with a reducing step). The surface microhardness of multicomponent chrome layers alloyed with titanium and boron is 20000 - 22000 MPa, which is due to the presence of the phase FeB. The microhardness of the alloyed Fe2В phase is 15000 – 16000 MPa. When chromium coatings are alloyed with titanium on the considered structural materials, the following phases are formed: (Fe,Cr)23C6, (Fe,Cr)7C3, Cr3C2, as well as phases: Fe2Ti, Cr2Ti. The surface microhardness of titanium-alloyed chromium coatings is: on steel 20 – H100= 16000 MPa, (phases: (Cr,Fe)23C6, (Cr,Fe)7C3, Fe2Ti, Cr2Ti, α- solid solution of Ti and Cr in α- iron), on steel 45 – H100 = 18000 MPa (phases: (Cr,Fe)23C6, alloyed with titanium, α-solid solution of chromium in iron with Cr2Ti inclusions), on U8 – H100= 19500 MPa (phases: directly on the outer side of the coating there is a zone of carbides (Fe,Cr)23C6, (Fe,Cr)7C3, Cr3C2, (Ti,Cr)C).