Tribological behavior of polydopamine/polytetrafluoroethylene coating on laser textured stainless steel with Hilbert curves

Shallow Hilbert curve patterns with easily programmable texture density were selected for laser texturing of stainless steel substrates.Two different texture path segment lengths(12 and 24 μm)and four different laser power percentages(5%,10%,15%,and 20%)were investigated.The textured and smooth substrates were coated with thin polydopamine/polytetrafluoroethylene(PDA/PTFE)coatings for tribological property assessment.The effects of texture density(texture area coverage)and laser power on the durability and friction of the coated surfaces were studied.Laser texturing the substrates improved the coating durability up to 25 times,reduced the friction coefficient,and prevented coating global delamination.The textures fabricated with a laser power of 15%and a texture path segment length of 12 μm yielded the best coating durability.The textures provided the interlocking for the PTFE coating and thus prevented its global delamination.Furthermore,the PTFE inside the texture grooves replenished the solid lubricant worn away in the wear track and prolonged the coating wear life.