Enhanced properties of alumina coating produced by combining plasma electrolytic oxidation and ultrasonic shot peening

A short -duration ultrasonic shot peening (USP) is used as a post -treatment to plasma electrolytic oxidation (PEO) coatings produced on a 2017 aluminium alloy under various sparking regimes (arc or soft) and time durations. USP is detrimental on PEO layers produced for short durations and under the arc regime because the typical pancake structure at the topmost surface is partially blasted. In contrast, PEO layers grown under the soft regime not only keep their structural integrity after short duration USP but also experienced a densification of their internal sublayer and a resurfacing of the sponge structure at the external sublayer. Under the specific PEO soft regime, the proposed duplex surface treatment makes the coating harder with a higher fracture toughness compared to the as -produced PEO coating.