Electroless NiP coatings, known to have excellent properties such as corrosion and wear resistance, hardness, lubricity, uniformity of deposit regardless of geometries, solderability and bondability and nonmagnetic properties, are widely used in the mechanical, chemical and electronic industries. An improvement of some of those properties can be achieved by the incorporation of hard particles (SiC, B4C, Al2O3 and diamond) and dry lubricants (PTFE, MoS2 and graphite), resulting, in the last case, in a film with self-lubricating and excellent anti-sticking characteristics. This fact is reported by the work of several researchers that have investigated the wear behaviour of these coatings, using different wear testers and mostly in nonlubricated conditions. However, in several mechanical applications the use of lubricants is needed because the friction should be very small. In this stage, and to meet these requirements, most modern lubricants are complex formulated products consisting of 70–90% base oils mixed with functional additives to modify the natural properties (i.e. cold stability, oxidation stability, hydrolytic stability, viscosity and viscosity index, corrosion) and fulfil the requirements for the fluid. The base oil can be mineral, vegetable or synthetic. Another aspect that should be considered is that there is an increasing demand for environmentally compatible lubricants, particularly in areas where they can come into contact with water, food or people. Electroless nickel (EN) coatings are used in a wide range of applications concerning their excellent mechanical and tribological properties. The incorporation of solid lubricants, such as polytetrafluoroethylene (PTFE), could even improve the properties of the EN coatings. Above all, we can achieve a film with self-lubricating and excellent anti-sticking characteristics. These uses of electroless nickel coatings are widespread in dry contacts. However, it is well known that in the mechanical components there are a large number of applications that require especially low friction, usually not compatible with the use of unlubricated contacts. Moreover, nowadays, there is a general concern with the environmental impact in the use of lubricants. The tendency is to use fluids with small environmental impact, reducing the contamination made by lubricants of mineral origin. Hence, the aim of the present work was to investigate and improve the understanding of the behaviour of EN and EN + PTFE coatings under lubricated contacts using biolubricants.
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