Many industrial processes are dependent on the proper application of modern tribological knowledge for the purposes of maintaining equipment integrity and minimizing total energy losses. Consequently, the development of modern lubricants is vital for satisfying growing performance standards and increasingly stringent environmental regulations. Industrial lubricants are regulated based on demanding technical requirements and characteristics, such as high viscosity index, hydraulic stability, corrosion prevention, thermal stability, wide operating temperature ranges, demulsibility, and oxidative stability. Escalating environmental and sustainability concerns have shifted significance towards non-technical criteria for the evaluation of lubricants. Biodegradability and renewability are two influential factors in the discussion regarding the long-term sustainability of future tribological applications. Emphasis is placed on the development of environmentally friendly, non-toxic, and biodegradable lubricants that would minimize industrial pollution associated with oil-related spills and leakages. Bio-based lubricants, manufactured from renewable, organic resources, present themselves as viable alternatives to traditional petroleum-based lubricants. A major section of this review paper will provide a comparative analysis of renewable resource-based lubricants and mineral oil-based lubricants in terms of their chemical properties and respective advantages. Further discussion concerning biolubricants and use of non-edible plant feedstocks will highlight the clear economic and environmental incentives of implementing modern tribological knowledge. This review paper will conclude with the examination of the obstacles that modern day biolubricants must overcome and the future expectations of green tribology.

Dry friction and wear tests were performed with self-mated couples of SiC with 50 wt%TiC, SiC-TiB₂, Si₃N₄ with 30 wt%TiN, Si₃N₄ with 5, 10 and 20 wt%BN and a binary carbo-nitride composite (Ti,Mo)(C,N) at room temperature and 40°C or 80°C. The results are compared with currently available SiC and Si₃N₄ materials. In a normal environment the examined ceramic composites used during these studies are able to form a lubricious oxide reaction layer or a film of an intrinsic solid lubricant on a hard substrate. The binary carbo-nitride composite had a wear coefficient smaller than 10⁻⁶ mm³ · N⁻¹ ·m⁻¹, sometimes smaller than 10⁻⁷ mm³ · N⁻¹ · m⁻¹, that was independent of temperature from ambient up to 800°C. At 22°C the addition of hexagonal BN reduced the friction of Si₃N₄. Simultaneously, the wear coefficient was independent of sliding velocity and below 10⁻⁶ mm₃ · N⁻¹ · m⁻¹. Friction and wear increased with increasing temperature. The addition of TiC to SiC reduced friction and wear. At room temperature, Si₃N₄−TiN exhibited a lower wear than Si₃N₄. At 800°C, the wear coefficient of Si₃N₄ was reduced by two orders of magnitude by the addition of TiN as TiO_2-x forming substrate. The addition of TiB₂ to SiC was only beneficial at 400°C and above 0.5 m·s⁻¹ compared to SiC by decreasing the wear coefficient.