Effect of Ductile Thermal Spray Coatings on Fatigue Performance of 7075-T651 Aluminum Alloy

The fatigue behaviour of 7075-T651 Al alloy with ductile aluminum thermal sprayed coatings deposited by four different commercial arc spray devices (guns) has been characterized. Coated specimens as well as polished and shot peened specimens were evaluated under fully reversed uniaxial loading at a constant amplitude of \uc2\ub1225 MPa. While the shot peening pretreatment was observed to increase the fatigue resistance of polished specimens, application of the coatings subsequently reduced fatigue life to below that of the original polished coupons. Changes in the residual stress state of the shot peened surface were identified as the most likely source of these reductions, even though no microstructural changes in the substrate were perceptible. Variations in fatigue life were also observed between the coatings resulting from the four spray guns. The roles of surface roughness and coating delamination in producing these decreases were investigated and stress concentrations resulting from coating delamination were identified as the primary detrimental factor affecting fatigue resistance.On a caract\uc3\ua9ris\uc3\ua9 le comportement de fatigue de l\ue2\u20ac\u2122alliage d\ue2\u20ac\u2122Al 7075-T651 avec des rev\uc3\uaatements ductiles d\ue2\u20ac\u2122aluminium d\uc3\ua9pos\uc3\ua9s par m\uc3\ua9tallisation \uc3\ua0 chaud au moyen de quatre dispositifs (fusils) commerciaux diff\uc3\ua9rents de fusion en arc \uc3\ua9lectrique. On a \uc3\ua9valu\uc3\ua9 des \uc3\ua9chantillons rev\uc3\uaatus ainsi que des \uc3\ua9chantillons polis et trait\uc3\ua9s par grenaillage sous une charge uniaxe enti\uc3\ua8rement altern\uc3\ua9e \uc3\ua0 une amplitude constante de \uc2\ub1 225 MPa. Alors que l\ue2\u20ac\u2122on a observ\uc3\ua9 que le pr\uc3\ua9traitement par grenaillage augmentait la r\uc3\ua9sistance \uc3\ua0 la fatigue des sp\uc3\ua9cimens polis, l\ue2\u20ac\u2122application des rev\uc3\uaatements r\uc3\ua9duisait ult\uc3\ua9rieurement l\ue2\u20ac\u2122endurance au-dessous de celle des \uc3\ua9chantillons polis originaux. On a identifi\uc3\ua9 des changements dans l\ue2\u20ac\u2122\uc3\ua9tat de contrainte r\uc3\ua9siduelle de la surface trait\uc3\ua9e par grenaillage comme \uc3\ua9tant la source la plus probable de ces r\uc3\ua9ductions, m\uc3\uaame si aucun changement de la microstructure dans le substrat n\ue2\u20ac\u2122\uc3\ua9tait perceptible. On a \uc3\ua9galement observ\uc3\ua9 des variations dans l\ue2\u20ac\u2122endurance entre les rev\uc3\uaatements r\uc3\ua9sultant des quatre fusils de m\uc3\ua9tallisation. On a investigu\uc3\ua9 le r\uc3\ub4le de la rugosit\uc3\ua9 de surface et du d\uc3\ua9laminage du rev\uc3\uaatement sur la production de ces diminutions et l\ue2\u20ac\u2122on a identifi\uc3\ua9 la concentration des contraintes r\uc3\ua9sultant du d\uc3\ua9laminage du rev\uc3\uaatement comme facteur d\uc3\ua9favorable primaire affectant la r\uc3\ua9sistance \uc3\ua0 la fatigue.Peer reviewed: YesNRC publication: Ye

RRA Heat Treatment of Large Al 7075-T6 Components

NRC publication: Ye