Effect of TiO 2 addition on the microstructure and nanomechanical properties of Al 2 O 3 Suspension Plasma Sprayed coatings

Abstract

• Al 2 O 3 and Al 2 O 3 –13 wt% TiO 2 coatings were deposited by suspension plasma spraying. • Coating microstructure was formed by dense melted zones embedded in a softer matrix. • The addition of TiO 2 leads to a higher melting rate of the initial feedstock. • Al 2 O 3 –TiO 2 coating presents higher hardness and Young's moduli than pure Al 2 O 3 layer. Alumina–titania coatings are widely used in industry for wear, abrasion or corrosion protection components. Such layers are commonly deposited by atmospheric plasma spraying (APS) using powder as feedstock. In this study, both Al 2 O 3 and Al 2 O 3 –13 wt% TiO 2 coatings were deposited on austenitic stainless steel coupons by suspension plasma spraying (SPS). Two commercial suspensions of nanosized Al 2 O 3 and TiO 2 particles were used as starting materials. The coatings microstructure and phase composition were fully characterised using FEG-SEM and XRD techniques. Nanoindentation technique was used to determine the coatings hardness and elastic modulus properties. Results have shown that the addition of titania to alumina SPS coatings causes different crystalline phases and a higher powder melting rate is reached. The higher melted material achieved, when titania is added leads to higher hardness and elastic modulus when the same spraying parameters are used.