Research On Plasma Materials Surface Modification Of The Extruding Die

ABSTRACT:Since there is enormous frictional resistance between the mould of continuous extrusion machine and blanks, the mould wears serious and has a short life. Faced with this situation, in this paper, the pulsed high energy density plasma (PHEDP) thin solid film deposition process and direct current plasma beam cladding technology were adopted to reinforce the quick-wear surface the continuous extruding dies. By improving high temperature wear resistance and reducing friction coefficient of the continuous extruding dies quick-wear surface, the service life of the continuous extruding dies will be highly improved.Nitrogen with a concentration of more than99.9at.%was used as working gas. The inner and outer electrodes are made of titanium.0.45%C carbon steel was used as matrix. Using optimized experimental parameters, the TiN film was deposited on0.45%C carbon steel matrix. The microstructure, surface compositions and depth profile of the film were analyzed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and scanning electron microscopy (SEM).The hardness profile and tribological behavior of the film were determined with nano-indenter and dry sliding wear tester, respectively. The results showed that the microstructure of the film was dense and uniform and mainly composed of titanium nitride phases. A wide mixing interface existed between the film and the substrate. The film possessed very high value of nanohardness. The wear resistance of the film was excellent and the value of the friction coefficient of the film was low under dry sliding wear test conditions.Using Ni-46.25Ti-11.5625C-7.5CaF2(wt.%), Ni-45Ti-11.25C-10CaF2(wt.%) and Ni-43.75Ti-10.9375C-12.5CaF2(wt.%) mixed alloy powders as the precursor materials respectively, the (TiC+CaF2)/y-Ni composite coatings with different CaF2have been produced on0.45%C carbon steel matrix. Microstructure of the composite coatings was characterized, and the micro-hardness and high temperature tribological properties were tested. The test results showed that the plasma clad (TiC+CaF2)/y-Ni composite coatings have tiny uniformly microstructure, and are totally metallurgically bonded to the substrate. The coatings have the microstructure feature that irregular blocky primary phases TiC and small amount of flake like CaF2are uniformly distributed in the solid solution matrix y-Ni. The coating performed excellent high temperature wear resistance. The CaF2contents of the plasma clad coatings have a remarkable influence on high temperature wear resistance. With the increasing of the CaF2contents, high temperature wear resistance become higher and friction coefficients become lower.