Microarc oxidation technology for surface modification of metal.
Microarc oxidation allows to obtain coatings for various purposes: heat-resistant, insulating, decorative, corrosion-resistant and protects against fretting corrosion in particular, wear-resistant as well as being a sublayer for deposition of polymeric materials.
Microarc oxidation is one of the most promising methods of surface treatment of metal surfaces due to its (surface) modifications. Microarc oxidation allows to obtain coatings for various purposes: heat-resistant, insulating, decorative, corrosion-resistant and protects against fretting corrosion in particular, wear-resistant as well as being a sublayer for deposition of polymeric materials.
The essence of the method lies in the fact that by passing a large current density through the interface metal-electrolyte conditions are created when the tension at the interface becomes higher than its dielectric strength on the surface of the electrode occur microplasma discharges with high local temperatures and pressures. The result of microplasma discharges is the formation of a coating layer, consisting of oxidized forms of the elements of the metal framework and the components of the electrolyte. Depending on the mode of microplasma oxidation and the composition of the electrolyte to obtain ceramic coatings with unique characteristics and a wide range of applications.
Surface modification and structuring of the transition layer is achieved by realization of the sequence of forming periodic series of electrical impulses of a special form. By controlling the amplitude, duration, fronts and sections, phase ratio, by combining positional and frequency of pulses is generated a plasma discharge. They synthesize the solid structure of metal-ceramic compounds (composites) of high temperature polymorphic modifications of elements of the substrate with a certain selectivity depending on the composition of the normal-activate or fine-pestiviruses environment (pH and electrolyte composition).
Developed technological processes of coating based on aluminum oxide, silicon dioxide, etc.
Microarc oxidation in the scientific literature has other names: plasma-electrolytic synthesis of oxide layers, a plasma-electrolytic oxidation, oxidation in the electrolytic plasma surface treatment in electrolytic plasma, micro plasma electrolytic oxidation, anodic spark oxidation.
– the ability to create a heavy-duty coatings with unique characteristics
– receive multiple security features in the complex
– practically infinite service life of electrolyte,
– possibility of processing of geometrically-complex parts, including the inner surface of the pipe,
high scattering ability of the electrolyte (the coating is applied in the holes and cavities with a minimum of difficulty),
– no need for special surface preparation before coating and machining after coating,
– obtaining of different coatings on the same material
– ecological cleanness of the production process,
– low cost coverage
– no harmful gaseous emissions into the atmosphere,
– making the surface of multiple types of functionality,
– ability to integrate the new MDO equipment into the existing production lines,
– does not require special surface preparation
– the surface of the workpiece from a few square millimeters to meters.
Production line for micro-arc oxidation comprises:
– power equipment – specialized sources of supply,
– baths, in which the training surface treatment and rinsing,
– manipulator for movement of the suspension parts (in the case of mass production),
– metal structures for placing baths and a manipulator,
– auxiliary machinery distiller, pumpfilter to clean and transfer solutions, reserve vessels, devices of control of coating quality and condition of the electrolyte.
From power sources to the terminals of the baths serves the current pulses of a certain shape, this item performs the role of the anode, as the cathode serves as a bath or additional electrodes, usually stainless steel.
Line for micro-arc oxidation is different:
– relatively low power consumption,
– high performance
– small production area,
– ease of maintenance and minimum of personnel,
– environmental safety,
– availability of reagents and other consumables used.
The number of necessary operations during the microarc oxidation is significantly less than traditional anodizing processes. This follows from the absence of numerous preparatory operations and ecological compatibility of applied solutions. It includes the following operations: loading, degreasing, rinsing, application of MDO coating, trapping, washing, unloading. After downloading and mounting the pieces on a hanger degreasing is performed, after which the parts are delivered for processing. For large scale production after the bath of the coating tub to put the trap for more efficient use of chemicals and rinsing water.