Adhesion of HVOF Sprayed Diamond-Containing Nanostructured Composite Coating
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Adhesion of HVOF Sprayed Diamond-Containing Nanostructured Composite Coating Dr. Maksim V. Kireitseu and Ion Nemerenco Department of Mechanics and Tribology Institute of Mechanics and Machine Reliability (INDMASH), National Academy of Sciences of Belarus Lesnoe 19 - 62, Minsk 223052, Belarus E-mail: [email protected] ABSTRACT In the present paper mechanical properties of HVOF sprayed diamonds-containing aluminum oxide composite coating have been investigated. Crystallographic and morphologic texture was measured. Diamonds nanoparticles may improve fracture resistance of aluminum oxide-based coating. Investigations of thermally sprayed coatings by the test revealed high accuracy, speed and reliability of the test. It is also thought that the composite coatings will have better thermal conductivity and thermal shock resistance than that of aluminum oxide-based coatings. INTRODUCTION Ultra-dispersed diamonds (UDD) are the new synthetic diamond powders produced by chemical purification of explosion products. Nanoparticles of UDD have spherical and isometric form with no crystalline facets and a fractional structure of clusters [1, 2]. They may be presented as a high-dispersed powder. The diamond nanoparticles are being used for many applications because of its highest known hardness, excellent wear resistance and high thermal conductivity. On the other hand, applications of single diamond-containing coating are still limited because of its poor fracture resistance and adhesion to substrates. Needless to say, fracture and adhesion strength between coating and substrate are the most important parameters to characterize its quality and effectiveness of related technologies. In general, adhesion may determine reliability and durability of the coatings. Adequate coating-substrate adhesion under service conditions is a prerequisite to the satisfactory performance of any thermally sprayed ceramic-coated-metal system. Were the coatingsubstrate bond to fail in a given case and detachment of the coating from its substrate to occur as a consequence, the purpose for which the coating was applied would not likely be served. Thus, it becomes plain that the nature of the coating-substrate bond and the mechanisms by which it may fail must be known and understood clearly. Researches [1-8] indicates that the adhesion generally decays with time at a rate that depends on mechanical loads, temperature and chemical makeup of the environment, the coating porosity, and the state of stress at the coating-substrate interface and within the coating. Moreover, it has been studied [3-14] that adhesive and/or cohesive failure of thermally sprayed ceramic-metal systems proceeds by means of a complex set of rate processes. It follows that investigations of coating-substrate adhesion should be conducted under actual and/or closely simulated service conditions to the extent feasible. This becomes particularly difficult when the coating-substrate system must be subjected to elevated applied load, localized stresses and temperatures during
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