Carbide-Cobalt-Chromium Thermal Spray Powder

Tungsten carbide belongs to the ceramic phase and has the advantages of high melting point, high hardness, high electrical and thermal conductivity, stable chemical properties, etc. It is an ideal material for preparing wear-resistant and corrosion-resistant coatings. However, due to the high melting point and high hardness of tungsten carbide (WC), the adhesion between the sprayed tungsten carbide particles and the substrate is poor, and oxidation occurs when air temperature raise. Therefore, the pure tungsten carbide powder is rarely used alone as a thermal spray powder material, and it is usually required to add a metal or alloy such as Co, Ni, Ni-Cr. The binder phase is used as a sintered powder or a coated powder for thermal spraying.

The tungsten carbide-cobalt-chromium thermal spray powders are usually prepared by a melting method, a sintering crushing method, a plasma spheroidizing method, a conventional agglomeration sintering method, etc., but these preparation processes has the problem of long cycle, low production efficiency and high energy consumption.

Thus, researchers have provided a method for preparing tungsten carbide-cobalt-chromium thermal spray powder, which has the problems of long production cycle, low production efficiency and high energy consumption for the conventional method. The main processes are as follows:

Firstly, 86 wt% tungsten carbide powder,10 wt% cobalt powder, and 4 wt% chromium powder are added into the ball mill, while adding deionized water, controlling the solid content is 75%, Then it is wet grinding, the time is 12h;

After wet grinding, the average particle size of the mixed powder is 0.1 μm to 10 μm, and polyethylene glycol containing 2% by mass of the mixed powder is added. After stirring for 2 hours, granulation is carried out in a spray drying tower to obtain a granulated powder; At 260 ° C, the outlet temperature is controlled at 110 ° C; the granulated powder is passed through a 200 mesh and 900 mesh double-layer vibrating screen to obtain a sieve powder having a particle size of 15 to 75 μm, and the 200 mesh sieve powder and the 900 mesh sieve powder are returned. Wet grinding; the obtained sieve powder is degreased in a tube furnace at a temperature of 800 ° C for 4 hours to fully remove the polyethylene glycol in the granulated powder; the degreased powder is placed in a vertical high temperature sintering furnace Rapid sintering, the powder continuously and uniformly passes through the heating zone and the cooling zone in a free-falling motion, and sintering is completed in the heating zone to obtain a sintered powder; the feeding mode is a vibrating mesh feeding, the protective atmosphere is nitrogen, and the sintering temperature is 1250. °C, sintering time 0.4s, cooling method is air cooling; the sintered powder is separated by air flow to a powder with a particle size distribution between 15 microns and 45 microns, which is WC-10Co-4Cr thermal spray powder.

Finally, the WC-10Co-4Cr thermal spray powder having a spherical shape including spherical, spheroidal and non-spherical was obtained, and the powder was tested according to GB1482-1984: fluidity <25s/50g, loose density <3.5g/cm3. The prepared tungsten carbide-cobalt-chromium thermal spray powder has uniform composition, high sphericity and good fluidity, and can fully meet the requirements of thermal spraying, and is suitable for preparing high-performance cemented carbide coating, and can be widely applied in: aerospace, machinery manufacturing and petrochemical industries.

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