Super Low Friction Property of DLC Lubricated With Ester-Containing Oil: Part 1 — Friction Properties Evaluated in Rig Tests

This paper presents a material combination that reduces the friction coefficient markedly to a super low friction regime (below 0.01) under boundary lubrication. Friction tests were conducted with a test rig consisting of three pins pressed against a rotating disc, as shown in Fig. 1. The pins were made of bearing steel AISI52100 and the disc was made of carburized steel SCM415, which was coated with a diamond-like-carbon (DLC) film. The test conditions were as follows. Pins: Fixed, not rotating; DLC: CVD a-C:H, PVD ta-C; Lubricant: 5W-30 API SG Engine oil; Ester-containing oil (PAOES1): Poly alpha-Olefin containing 1 mass% of glycerol mono-oleate; Pressure: 0.7 Gpa; Sliding speed: 0.03–1m/s; Oil temperature: 353K (80 deg. Celsius).