Tribological evaluation of sulfurnitrided gears without liquid lubricant

• Published in: Kikai Gakkai ronbunshū = Transactions of the Japan Society of Mechanical Engineers Vol. 87; no. 895; p. 20-00267
• Main Authors: HORIE, Kazuya, NANKO, Makoto, NISHIWAKI, Satoru
• Format: Journal Article
• Language: Japanese; English
• Published: The Japan Society of Mechanical Engineers 2021
• Subjects: Dry lubrication; Solid lubrication; Sulfurrnitriding; Surface treatment; Wear test
• ISSN: 2187-9761; 2187-9761
• DOI: 10.1299/transjsme.20-00267

Sulfurnitriding, one of various surface treatments for mechanical components made of steels realizes solid lubrication for decreasing friction force of each contact point and keeping lubricating condition on the surface. Any tribological data on sulfurnitrided steel gears have not been published. In this study, friction performance of sulfurnitrided gears made of low-carbon steels (JIS-S45C) was investigated. Wear tests of the gears were conducted at room temperature without any lubrication. The gears with different treatments such as non-treated, as-nitrided, as-carbonized, as-quenched and as-induction-hardened ones were applied to the same low-carbon steel for comparison. The amount of wear of the gears was decreased by applying the all surface treatments. The gears with the sulfurnitridation show smaller wear than others while the surface hardness of the gears was comparable or lower than the others. In particular, the surface treatment combining of sulfurnitridation and nitridation showed the lowest value of the amount of wear. The FeS layer formed by the sulfurnitriding is approximately 1 μm in thickness which is much lower than the amount of wear after 4 h in test time. Lubrication effects on the FeS layer remains after removing the layer. As well, nitridation after sulfurnitriding is effective to improve a solid lubrication performance for low-carbon gears at room temperature in air.