Effect of SiO2 and PTFE additives on dry sliding of NiP electroless coating

The aim of the present work is to study the effect of silicon dioxide and polytetrafluoroethylene (PTFE) additives on NiP coating performance under dry (unlubricated) conditions in unidirectional and reciprocating sliding modes in Ball-on-Flat configuration. Yttria-stabilized zirconia and chrome steel balls were used as counterbodies. Microstructural examination of specimens was conducted by a SEM with EDS. It was found that in contact with steel ball both additives were beneficial, while addition of SiO2 particles was detrimental for contact against ceramic ball. The highest improvement of tribological performance was obtained for NiP coated samples having PTFE or mixed additives.

► NiP–SiO2–PTFE coatings are deposited and tested against steel and ceramic balls.
► PTFE addition to NiP is beneficial in all conditions tested.
► SiO2 addition to NiP is beneficial only for steel counterbody.
► Scanning method for testing of coatings is proposed and coatings evaluated.
► Supply of fresh coating to the contact zone influence load carrying capacity.