Thermal spraying alternative to electroplating hard chrome

       Chrome electroplating is a traditional surface electroplating technology that has been used for nearly a hundred years. The chrome plating layer has high hardness, wear resistance, corrosion resistance, and can keep the surface bright for a long time. The process is relatively simple and the cost is low. For a long time, in addition to being a decorative coating, chrome plating has also been widely used as a wear-resistant and corrosion-resistant coating for mechanical parts. In addition, electroplating hard chrome plating technology is often used to repair damaged parts. However, Cr6+ generated during electroplating of hard chrome can cause serious environmental pollution problems. Chromium itself is an inactive element, which can be safely used in daily necessities and artificial joints, etc., but the chromic acid solution is used in the chrome plating process, and a large amount of hydrogen is generated during the chrome plating process. When the hydrogen bubbles burst, the chromic acid solution will be sprayed. If it enters the air, it will produce acid mist, which contains carcinogenic Cr6+; in addition, the chrome plating process will also produce a large amount of toxic waste and wastewater containing Cr6+. Therefore, the control of chrome plating process in various countries is becoming more and more strict.



Thermal spraying technology is a process in which the coating material (powder or wire) is fed into a certain heat source (arc, combustion flame, plasma, etc.) . The process is easy to operate, flexible and efficient, and there are many kinds of coating materials, which can be metals, alloys, ceramics, cermets or plastics. In recent years, high-energy and high-speed thermal spraying equipment has come out one after another, especially high-energy plasma spraying, three-cathode plasma spraying



The emergence of thermal spray coating and high-speed flame spraying (HVOF) equipment has overcome the weakness of thermal spray coating with many pores and low bonding strength, and the coating quality has made a qualitative leap, laying a solid foundation for thermal spray coating to replace electroplating hard chromium. technical basis. In recent years, the use of thermal spraying instead of hard chrome plating has carried out more comprehensive and in-depth research on coating materials, spraying technology, coating properties, coating post-processing technology and coating application. From the obtained results, the thermal spray coating can not only achieve the mirror roughness of the chrome layer, but also greatly exceed the chrome layer in terms of hardness and wear resistance, and can completely replace hard chrome in some applications, especially some Large workpieces are subject to severe wear and corrosion.