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During gear shifting, the contact between teeth composes a tribological system of considerable importance regarding energy dissipation in road vehicles. Improvement of tribological system efficiency leads to costs and pollutant emission reductions. Powder metallurgy (PM) is a near-net-shape technique that allows the production of parts with complex geometry - such as gears, lower costs and larger range of material utilization compared to other manufacturing processes. Furthermore, the presence of pores in sintered material could be a beneficial factor for friction reduction and wear resistance, due to oil reservoir and debris trapping effects, and film thickness variation that could enhance lubricant load support capacity. This work aims to evaluate the lubricant effect on support capacity due to surface pores in sintered steel with different levels of porosity. Results were compared with standard gear material based on friction coefficient results.

Carbon-based coatings are used in several industrial applications, usually to promote improved wear and friction behaviors. In this work, two carbons based coatings are analyzed: a non-doped amorphous Diamond Like Carbon (DLC), produced by a Plasma-Enhanced Chemical Vapor Deposition (PECVD) process, and a Tungsten doped DLC (W-DLC), produced by a Physical Vapor Deposition (PVD) process. Mechanical properties (hardness and modulus of elasticity) are measured by nanoindentation technique using the Hysitron TI950 triboindenter, while the tribological aspects of the coatings (wear behavior and coefficient of friction) are evaluated by reciprocating motion tests on an Optimol SRV v4 tribometer. The DLC presented higher indentation hardness and modulus of elasticity when compared to the W-DLC. Results also indicate that the DLC shows lower coefficient of friction and higher critical loads to present coating delamination when compared with W-DLC.