Structural features and tribological properties of multilayer high-temperature plasma coatings

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 3 2024 Conclusion High-temperature coatings obtained by plasma spraying consist of successively applied layers: the first inner (metal) layer is obtained by spraying self-fluxing powders of two different compositions of Fe-CrSi-Mn-B-C system (composition 1) and Fe-Ni-Si-Mn-B-C system (composition 2); the second layer is a transitional layer obtained by spraying a mixture of high-temperature powders of compositions 1 or 2, with Fe powder in the ratio of 50:50 and the outer (metal-oxide) layer is obtained by spraying Fe powder in an oxidizing atmosphere to form an oxide layer consisting of a mixture of iron oxides (FeO + Fe2O3 + Fe3O4) on the surface. The total thickness of the obtained coatings is 800–850 µm. The inner (metal) layer is characterized by high hardness (up to 1,030 HV 0.1 for coating composition 1 and 745 HV 0.1 for coating composition 2) and Re values, which indicates the ability of this layer to resist mechanical stress without plastic deformation in the elastic region. High plasticity indices of outer layers (creep CIT and plastic component of work φ) are established, the purpose of which is to act as a lubricant under high operating loads. Under conditions of dry sliding friction, it is shown that coating A has increased wear resistance compared to coating B; the friction coefficient for coating A is f = 0.3, the friction coefficient for coating B is f = 0.4. The study of the wear surfaces showed that on the surface of the obtained coatings after sliding friction tests at the load of 30 and 75 N the processes of seizure develop, and at increasing the load to 100 N and 130 N there is a transition to wear by the mechanism of plastic displacement, which corresponds to a decrease in the magnitude of wear. Under all selected test loads under conditions of dry sliding friction, high-temperature layers of coatings of both compositions are preserved at the maximum load of 130 N. After the sliding friction tests, a significant surface smoothing and a reduction in the arithmetic mean deviation of the Ra profile are recorded. References 1. Guzanov B.N., Kositsyn S.V., Pugacheva N.B. Uprochnyayushchie zashchitnye pokrytiya v mashinostroenii [Reinforcing protective coatings in engineering industry]. Ekaterinburg, UrO RAN Publ., 2003. 244 p. ISBN 5-76911405-3. 2. Serin K., Pehle H.J. Improved service life for hot forming tools in seamless tube plants. Stahl und Eisen, 2014, vol. 134 (11), pp. 161–174. 3. Sivakumar R., Mordike B.L. High temperature coatings for gas turbine blades: a review. Surface and Coatings Technology, 1989, vol. 37 (2), pp. 139–160. DOI: 10.1016/0257-8972(89)90099-6. 4. Podshivalkin S.A., Torbeev A.N. Struktura i svoistva oksidirovannykh pokrytii [Structure and properties of oxidized coatings]. Master’s Journal, 2012, no. 2, pp. 91–98. (In Russian). 5. Fomin A.A., Steinhauer A.B., Lyasnikov V.N., Wenig S.B., Zakharevich A.M. Nanocrystalline structure of the surface layer of plasma-sprayed hydroxyapatite coatings obtained upon preliminary induction heat treatment of metal base. Technical Physics Letters, 2012, vol. 38 (5), pp. 481–483. DOI: 10.1134/S1063785012050227. 6. Sazonenko I.O., Zemuov V.A., Yurchak A.N. K voprosu povysheniya stoikosti opravok proshivnykh stanov [To the matter of stabilization of saddles of punch mills]. Lit’e i metallurgiya = Foundry Production and Metallurgy, 2012, no. 4, pp. 135–138. (In Russian). 7. Pukhov E.V., Zagoruyko K.V. Rezul’taty eksperimental’nykh issledovanii iznosostoikosti poverkhnosti kolenchatogo vala, vosstanovlennoi metodom gazoplamennogo naneseniya samoflyusuyushchikhsya poroshkov [The results of experimental studies of the wear resistance of the surface of the crankshaft restored by the method of flame application of self-fluxing powders]. Mezhdunarodnyi tekhniko-ekonomicheskii zhurnal = The International Technical-Economic Journal, 2020, no. 4, pp. 45–52. DOI: 10.34286/1995-4646-2020-73-4-45-52. (In Russian). 8. Manoilo E.D., Radchenko A.A., Shardakov S.N. [Continuous gas-flame coating of self-fluxing alloy powders on rod couplings of oil pumps]. Poroshkovaya metallurgiya: inzheneriya poverkhnosti, novye poroshkovye kompozitsionnye materialy. Svarka [Powder metallurgy: surface engineering, new powder composite materials. Welding]. Collection of reports of the 13th International Symposium. Pt. 2. Minsk, 2023, pp. 171–186. (In Russian).

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