The influence of duplex coatings on tribomechanical properties of ceramic coating

U radu su opisana dva postupka nanošenja slojeva prevlake. Prvi sloj Al2O3 nanesen je postupkom plazma naštrcavanja na nehrđajući čelik (EN X22CrMoV121). Nakon njega je nanesen sloj ZrO2 postupkom sol-gel, uranjanjem. Parametri koji su se mijenjali pri sol-gel postupku su: temperatura toplinske obradbe ZrO2 sloja (400ºC, 700ºC, 1000ºC) i broj uranjanja u otopinu kod temperature 700ºC (ponavljan 4 i 8 puta), kako bi se vidio njihov utjecaj na svojstva prevlake. Na prevlakama je provedena materijalografska analiza ispitivanih ZrO2 prevlaka, te je izmjerena debljina, tvrdoća i modul elastičnosti. Ispitivana je otpornost na brazdanje prevlaka, otpornost na abraziju te definiran koeficijent trenja metodom "Ball on disc". Rezultati provedenih laboratorijskih ispitivanja pokazali su da različite temperature toplinske obradbe, kojoj se podvrgavaju uzorci prevlaka nakon geliranja i sušenja i broj slojeva ZrO2, utječu na cjelovitost prevlake kao i na mehanička svojstva prevlaka. Nanošenje prevlake ZrO2 na Al2O3 prevlaku značajno smanjuje koeficijent trenja u odnosu na uzorke bez ZrO2 prevlake. The dissertation describes a method of coating which combines two different methods of producing the layers. The first layer is Al2O3 produced by plasma spraying which was deposited on the stainless steel (EN X22CrMoV121) substrate. After that, ZrO2 layer was deposited on the Al2O3 coating by a sol-gel process using dip coating technique. During the sol-gel procedure, different annealing temperature of ZrO2 layer (400ºC, 700ºC, 1000ºC) and the numbers of dipping at temperature 700ºC (four and eight times) were performed in order to see their influence on properties of coatings. Materialographic analysis has been performed on studied ZrO2 coatings, and their thickness, hardness and Young modulus have been measured. The study includes resistance to grooving, resistance to abrasion and determining friction coefficient by "Ball on disc" method. The results of the performed laboratory studies have shown that the annealing temperature and number of layers of ZrO2 coating have influence on integrity of coating and on mechanical properties. ZrO2 coating on Al2O3 coating significantly decreased friction coefficient.