Friction and wear of electroless NiP and NiP + PTFE coatings

In the past 30 years, electroless nickel (EN) plating has grown to such proportions that these coatings are now found underground, in outer space, and in a myriad of areas in between. The first criteria to use electroless nickel generally falls within the following categories: corrosion and wear resistance, hardness, lubricity, uniformity of deposit regardless of geometries, solderability and bondability and nonmagnetic properties. An important property is the amorphous structure in the as-plated condition and the ability to heat treat the deposit by precipitation hardening. Moreover, in order to improve the mechanical and tribological properties of the EN coatings (NiP) further, a EN-polytetrafluoroethylene (NiP + PTFE) composite coating can be obtained that provides even greater lubricity than that which naturally occurs in the nickel–phosphorous alloy deposit. The aim of the present work was an investigation of the friction and wear characteristics of NiP and NiP + PTFE coatings in sliding contacts against hard chromium steel. The role of heat treatment of the coating is discussed.