Potential of thermal sprayed TinO2n1coatings for substituting molybdenumbased ring coatings

Purpose This paper aims to focus on the potential for substituting molybdenumbased piston ring coatings, which are recognized as allrounder by other candidate metallurgies. Another purpose is the tribological interaction of molybdenumbased and new triboactivereactive piston ring coatings with low SAP, polymer and metalfree as well as bionotox engine oils with highviscosity indices. Designmethodologyapproach Substoichiometric titanium dioxide composed of the Magnlitypes phases Ti4O7 17 per cent, Ti5O9 66 per cent, Ti6O11 17 per cent deposited by plasma spraying, a vacuum sprayed TiO1,93 and a plasmasprayed titaniummolybdenum carbonitride coated piston rings were compared to a stateoftheart molybdenumbased piston ring. They were tribologically characterized by means of BAM and SRV tests lubed under mixedboundary lubrication by factory fill engine oils, engine oils as blends of hydrocarbons with esters as well as prototype engine oils based on esters and polyglycols. Findings Overall, the molybdenum and titaniumbased ring coatings wore in the same order of magnitude. The ranking depends on the test used. The BAM test favours MKP81A PL72 more, whereas the SRV methods favour the TinO2n1 more. The different bionotox and lowash prototype engine oils with reduced additive contents displayed isoperformance regarding the tribological behaviour of common and triboreactive materials. They presented no visible weakness in wear resistance, coefficient of friction and extreme pressure properties. Research limitationsimplications The next steps have to confirm functional properties by different engine and endurance tests. Practical implications Titaniumbased piston ring coatings are overall more attractive, as they are primarily refined from titania, which is cheap and not rated at stock exchanges, and they present at least an isoperformance when compared with molybdenumbased ring coatings. Originalityvalue This supplier report displays the complete methodology in order to substitute molybdenum by titaniumbased piston ring coatings as well as illuminating the beneficial interaction with alternative engine oils in existing engine architectures.