Friction and outwearing of ceramic coatings formed by the microarc oxidation method

Abstract

The microarc oxidation (MAO) method by its power action on treated material can be referred to methods of surface strengthening by concentrated streams of energy. The local action of microarc discharges on a metal surface depends both on electric characteristics of microarc discharge and parameters of electrolyte and on characteristics of treated metal. Good wear resistance of MAO coatings is being explained by a high level of physical and mechanical characteristics and by their structural constitution. The aim of the investigations presented in this article is the estimation of MAO coating wear resistance compared with other wear-resistant materials. The basic trials of materials were conducted on abrasive outwearing using pin-ondisc friction schema. MAO layers with threadlike mono-crystals of α-Al 2 O 3 (emery) have the best mechanical and tribotechnical characteristics. Such microstructures have MAO coatings on aluminium alloys of the Al-Cu-Mg system -duralumin. They represent the most effective structure ensuring high wear resistance.

Antifriction properties increasing of ceramic MAO-coatings

“…Presently, both Russian [3][4][5][6][7] and foreign scientists [8][9][10]14,15 pay a lot of attention to the study of MAO coatings porosity. The fact is that the value of porosity significantly affects the physical, mechanical, and tribological properties of coating.…”

“…Studies of coatings formed by anodic-cathode microarc oxidation revealed their high hardness, wear resistance, adhesion and the ability to use them as a tribological material in various fields of engineering. [3][4][5][6]11 The power of micro-discharges (current density) and the electrolyte components significantly affect the coating porosity. Dense coatings with lower porosity can be achieved under minimum values of current density.…”

“…One can receive the coatings with high-wear resistance and high-adhesive strength to the substrate by this method. [3][4][5][6] The essence of MAO method is a combination of electro-chemical oxidation and electro-discharge phenomena on the anode-electrolyte border. The term ''microarc oxidation'' means electrochemical oxidation of anode (or details part) under the voltage higher than the voltage of sparking.…”

“…The composition of MAO coatings is a complex of aluminum oxides, which include hightemperature phase (a-Al 2 O 3 ) -corundum as well as low-temperature (g-Al 2 O 3 ) phase and elements or compounds from treated materials and electrolyte composition. 3,5 Now, microarc oxidation (also known as plasma electrolytic oxidation [8][9][10][11] ) is widely used in various industries -from medicine to aerospace, including oil and gas industry.…”

“…One can receive the coatings with high-wear resistance and high-adhesive strength to the substrate by this method. 3–6…”