Development and Application of Binary Suspensions in the Ternary System Cr 2 O 3 -TiO 2 -Al 2 O 3 for S-HVOF Spraying
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Development and Application of Binary Suspensions in the Ternary System Cr2O3-TiO2-Al2O3 for S-HVOF Spraying Annegret Potthoff1 • Robert Kratzsch1 • Maria Barbosa2,3 • Nick Kulissa2 Oliver Kunze2 • Filofteia-Laura Toma2
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Submitted: 14 September 2017 / in revised form: 14 February 2018 ASM International 2018
Abstract Compositions in the system Cr2O3-TiO2-Al2O3 are among the most used ceramic materials for thermally sprayed coating solutions. Cr2O3 coatings present good sliding wear resistance; Al2O3 coatings show excellent insulation behavior and TiO2 striking corrosion properties. In order to combine these properties, coatings containing more than one oxide are highly interesting. The conventional spraying process is limited to the availability of binary feedstock powders with defined compositions. The use of suspensions offers the opportunity for tailor-made chemical compositions: within the triangle of Cr2O3-TiO2Al2O3, each mixture of oxides can be created. Criteria for the selection of raw materials as well as the relevant aspects for the development of binary suspensions in the Cr2O3-TiO2-Al2O3 system to be used as feedstock for thermal spraying are presented. This formulation of binary suspensions required the development of water-based single-oxide suspensions with suitable behavior; otherwise, the interaction between the particles while mixing could lead up to a formation of agglomerates, which affect both the stability of the spray process and the coating properties. For the validation of this formulation procedure, binary This article is an invited paper selected from presentations at the 2017 International Thermal Spray Conference, held June 7-9, 2017, in Du¨sseldorf, Germany, that has been expanded from the original presentation. & Annegret Potthoff [email protected] 1
Fraunhofer Institute for Ceramic Technologies and Systems (IKTS), Winterbergstrasse 28, 01277 Dresden, Germany
2
Fraunhofer Institute for Material and Beam Technology (IWS), Winterbergstrasse 28, 01277 Dresden, Germany
3
Technische Universita¨t Dresden (TUD), Dresden, Germany
Cr2O3-TiO2 and Al2O3-TiO2 suspensions were developed and sprayed using the S-HVOF process. The binary coatings were characterized and discussed in terms of microstructure and microhardness. Keywords Al2O3-TiO2 binary suspension Cr2O3-TiO2 S-HVOF suspension spraying
Introduction The demand for multifunctional ceramic coatings in the Cr2O3-TiO2-Al2O3 system is continuously growing. For applications such as offshore piston rods, pump sealing seals or hydraulic cylinder rods, the coatings have to exhibit a combination of properties like improved hardness, wear and corrosion resistance. Since this is difficult to achieve by using only one oxide powder, two or more oxide powders may be combined. For the conventional thermal spraying process, the availability of fused feedstock powder composed of two oxides or more is limited, even though for industrial applications coatings with wide spectra of properties are needed. Su
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