Feasibility of fluidized bed CVD for the formation of protective coatings

Abstract

Attempts have been made to clarify the feasibility of a fluidized bed CVD (FBCVD) process as another method for the formation of cementing and diffusion coatings in order to improve wear, oxidation and corrosion resistance of metals. Treating agent powders consist of a donator, usually a powder of the metal, an alloy or a metal carbide or nitride of the coating forming metal, an activator, usually a halide or alkali metal halides, and a filler oxide, usually Al2O3, SiO2 etc. The precursors of the coating forming metal are formed “in situ” the fluidized bed reactor by the reaction of the donator with the activator. The bed can be fluidized by inert or reactive gas or gas mixtures like Ar, N2, Ar + H2 etc. As the parts can be charged and withdrawn while the furnace is at treating temperature, this process can be integrated into the heat treatment cycles. The FBCVD process was applied for the formation of Ti‐, V‐, Cr‐, Al‐, and Si‐bearing coatings. The produced coatings were dense and uniform over the whole specimen surface. According to the results, the use of the FBCVD process is promising since it can lead to a clean, flexible surface modification technology, combining adaptability with relatively low capital and operational costs.

Formation of Aluminide Coatings by a Low Temperature FBCVD Process

“…and diffusion (AI, Cr, etc.) coatings [2][3][4][5][6][7][8][9][10][11]. In this process, special donor powders of the to-be-deposited element had to be used because of the high treatment temperature.…”

General method for highly controlled preparation of ceramic hollow spheres from core‐shell structures

“…The spouted bed CVD technique combines the CVD and spouted bed processes, which could suspend the particles in the deposition zone by flowing a gas upwards through the bed layer with a precursor to complete coating on regular or irregular particles. The spouted bed CVD technique has good mixing effects and uniform exposure time of the particles to the CVD gases so that the different layers can coat the particles uniformly 23,24 . Therefore, the versatile spouted bed CVD has great potential values to prepare high‐quality hollow spheres from core‐shell structures.…”

Characterization and tribological properties of boride coatings of steels in a fluidized bed reactor

“…Fluidized bed technology (FBT) has been successfully used for the formation of different types of coatings, e.g. aluminizing, chromizing (Kingel et al , 1995; Pérez et al , 1999; Tsipas and Flitris, 2000), nitriding (Japka, 1983; Reynoldson, 1993), carburizing and carbonitriding (Reynoldson, 1993). On the other hand very limited information exists on boride coatings obtained using FBT, although this method is simple, efficient, environment friendly and the boride coatings have been reported to have an excellent combination of properties (Anil Kumar Sinha, 1997; Arai et al , 1986; Tsipas et al , 1999).…”