International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

Decision making methods have been examined within the context of conflicting criteria. Mechanical properties of a number of plasma sprayed coatings based on the modified alumina powder have been given for the purpose of comparative analysis. The modification has been performed by two different methods: 1) by cladding the alumina powder with Ti and Al metal sheaths where the PVD method has been employed; 2) by mechanochemical processing inside planetary ball mill with the titanium oxide nanopowder added. For coating selection, weighed characteristics technique has been used in conjunction with the digital logic and the proposed improved approach to the linear and non-linear data normalization. A conclusion has been made that the most effective, as far as the wear resistance parameter is concerned, are the coatings obtained as a result of the clad alumina powder spraying

Technique and equipment for plasma spraying of wear-resistant and corrosion-resistant coatings with enhanced adhesive strength was developed. Ceramic powders coated metal thin films were used for plasma spraying. Optimal conditions for deposition of the metal films on the particles of alumina powder (40…63µm fraction) by PVD process were obtained. Deposition of two- layer films on the powder particles was carried out. The first layer was titanium and the second layer was aluminum or copper. The titanium as adhesively-active element capable of wet alumina is necessary for increase the adhesion strength vacuum films as well as plasma sprayed coatings.

A special plasma-spray gun with external arc working in a mode of laminar plasma argon jet generation was designed. Such regime provides melting of the refractory ceramic core, saving metal films as well as localization of thermal effects during spraying process.
The results of testing coated specimens confirmed that the developed technique improves the physical and mechanical properties of the plasma sprayed composite coatings. The sprayed composite coatings were compared with coatings sprayed using pure alumina powders in terms of adhesion, wear and corrosion properties. The shear adhesion strength increases up to about 1.9 times, the wear resistance increases about 5 to 7 times, the corrosion resistance increases about 2.5 to 5 times.

The shear adhesion strength was measured at tension of coated specimen at room temperature by developed adhesion testing technique. The substrate was flat and dog-bone-shaped. The substrate with rectangular cross-section was partially coated with plasma- sprayed coating. The specimens were tested in uniaxial tension under displacement control. The tensile specimens were loaded to adhesion delamination of the coating. Sprayed coating was detached as a result of shear interface stresses.