13 The New Methods for Scuffing and Pitting Investigation of Coated Materials for Heavy Loaded, Lubricated Elements Remigiusz Michalczewski, Witold Piekoszewski, Waldemar Tuszyński, Marian Szczerek and Jan Wulczyński Institute for Sustainable Technologies - National Research Institute (ITeE-PIB) Poland 1. Introduction In modern technology due to the increase of the unit pressure, velocities, and hence temperatures in the tribosystems of machines, a risk of two very dangerous forms of wear exists. These forms are scuffing and pitting. Scuffing is a form of wear typical of highly-loaded surfaces working at high relative speeds. Scuffing is considered to be a localised damage caused by the occurrence of solid-phase welding between sliding gear flanks, due to excessive heat generated by friction, and it is characterised by the transfer of material between sliding surfaces. This condition occurs during metal-to-metal contact and due to the removal of the protective oxide layer of the metal surfaces (Burakowski et. al., 2004). A typical scuffing zone of gear teeth (Michalczewski et al., 2010) is illustrated in Fig. 1. Fig. 1. A typical scuffing wear of gear teeth Another form of wear is rolling contact fatigue (pitting). Pitting is a form of wear typical of highly-loaded surfaces working at a sliding-rolling and rolling contact, e.g. such components in transmissions like toothed gears and rolling bearings (Torrance et al, 1996). It is caused by the cyclic contact stress, which leads to cracks initiation (Libera et al., 2005). The lubricant is