Properties and Application Characteristics of Chromium Oxide Spray Powder
With the introduction of YAG laser engraving technology into the anilox roller industry, the quality standards for chromium oxide ceramic coatings are constantly increasing. These coatings need to not only extend the service life of the roller, but also require the engraving of 1500 lines per inch or more on this coating. If the porosity of the chromium oxide ceramic coating exceeds 1%, the number of meshes cannot be reached during engraving because the hole size will be larger than the mesh size. In addition, if hardness of the coating is not enough or the porosity is too high, it will be prematurely worn. Therefore, the quality of chromium oxide coatings is the most critical factors in the manufacture of high quality anilox rolls.
Chromium oxide (Cr2O3) is a dark green powder with a metallic luster and is a hexagonal or amorphous crystal. Its melting point is 2265 to 2435 degrees, and its density is 5.2g/cm3. It is a kind of neutral oxidation. Things. Plasma sprayed chromium oxide coatings are chemically stable, insoluble in acids, alkalis, salts, and various solvents. It has excellent resistance to media immersion and corrosion, and it resists high temperature erosion to corrosive gases containing H2S and SO2. It is extremely stable to atmosphere, fresh water, seawater and light but soluble in hot sodium bromide solution. The chromium oxide coating has excellent hydrophilic properties, which can form a uniform water film on the surface of the coating.
Physical properties of chromium oxide
Chromium oxide has great spraying process performance with a wide range of spray process specifications. It is less sensitive to overheating caused by spraying process, so it is not easy to crack when topical coating overheats. The sprayed layer is very dense and has a high bonding strength with the substrate, making it easy to perform grinding, polishing and other machining operations. However, the pure chromium oxide powder has a low deposition efficiency, which increases the coating cost. Chromium oxide coatings using flame spraying or plasma spraying are denser and insoluble in acid, alkali and alcohol. The coating can be used in the environment with chemically aggressive media after proper sealing.
It can be used as coatings resistant to abrasion, hard facing, erosion and cavitation below 540°C. It can also be used as corrosion-resistant coatings for components used in chemical media below 250°C (need to be properly sealed), such as pistons, plungers, chemical machinery shafts, pump seals, wear rings, slide valves, cylinder linings, exhaust fans, polishing and polishing fixtures, etc, and fiber abrasion resistant coatings like chemical fiber textile machinery Guide rollers, friction rollers, roller rollers, etc, and magnetic wear-resistant coatings like tape recorder heads,etc.
The as-sprayed Cr2O3 coating is deep dark green and has a strong hiding power. It has a high and stable thermal emissivity over a wide range of off-line wavelengths. It is commonly used in infrared radiation coating (such as electric heating tube coating)and high temperature magnetic wear-resistant coating and so on.
Since the coating is easy to grind to a small surface roughness and polished to the mirror surface with excellent lubricity to water, it can also be used as the wear-resistant and corrosion-resistant hydrophilic on the surface coating of printing machine water roller and other parts. We can use gas-stabilized plasma spraying, water-stabilized plasma spraying, supersonic plasma spraying, supersonic flame spraying, explosion spraying and powder flame spraying or other spraying technology to prepare coatings.
