Dry Sliding Wear Properties of a 7075-T6 Aluminum AlloyudCoated with Ni-P (h) in Different Pretreatment Conditions

摘要

Dry sliding wear behavior of electroless nickel-phosphorus (EN) coating of thickness �35 lm deposited onuda 7075-T6 aluminum alloy was studied. EN was deposited from a bath with sodium hypophosphite as audreducing agent. In as-deposited conditions, plating with 6-9 wt.% phosphorus has a mixture of amorphousudand microcrystalline phase. Three pretreatments of Zn (zincate), Ni strike and absorbed hypophosphiteudlayer were given to the substrate before EN coating to examine their wear performance. The surfaceudmorphology of the pretreatments was studied by a confocal laser scanning microscope. The performances ofudthese pretreatments of EN were evaluated by dry sliding wear studies and followed by SEM studies. Theudresults suggest that the wear behavior of EN mostly depends on the pretreatment conditions. Heat treatmentudat temperature of 400 �C can enhance the wear resistance properties for all types of pretreatmentudconditioned samples and in addition that the average coefficient of friction of 400 �C specimens (lav) hadudminimum value as compared to 200 �C specimens. Ni strike provided better interlocking adhesion betweenudEN and Al and this pretreatment noticeably improved the wear, frictional and hardness behavior of the ENudcoatings on 7075 Al substrate and further enhanced it by heat treatment of 400 �C/h.