EVALUATION OF HIGH VELOCITY OXYGEN FUEL (HVOF) Al/SiCp COATINGS AS CORROSION CONTROL COATINGS FOR MAGNESIUM ALLOYS

摘要

High velocity oxygen-fuel (HVOF) thermal spraytechnique has been used to fabricate Al and MMC(Al/SiCp) coatings on the AZ91 Mg alloy as acorrosion-control coatings. Corrosion behaviour of thecoated specimens had been evaluated byelectrochemical tests which revealed that some coatedspecimens presented an improvement on the corrosionbehaviour of the AZ91 substrate. Taguchi DOE methodhas been used to analyse the relationship between thespraying conditions, i.e. spraying distance, % SiCp infeedstock, number of layers deposited and gun speed,and the corrosion behaviour of the coated specimens. Inaddition, a relationship between the coatingcharacteristic, i.e. thickness, porosity, adhesion androughness, and the corrosion behaviour of the coatedspecimens had also been studied. Optimum sprayingconditions were fabricated and corrosion tested tovalidate the Taguchi DOE method analysis. Among thedifferent coatings features, thickness and compactnessseems to be the most relevant ones in terms ofcorrosion.