Authors : Sinan Sefertaş; Mehmet Yusuf Baran

Volume/Issue : Volume 11 - 2026, Issue 7 - July

Google Scholar : https://tinyurl.com/3tvt27wr

Scribd : https://tinyurl.com/ynemwwc5

DOI : https://doi.org/10.38124/ijisrt/26jul967

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Abstract : This study investigates the gas nitriding process applied to C35 medium-carbon steel to improve the surface properties of piston rods used in automotive tailgate and hood gas springs. In gas spring systems, the surface characteristics of the piston rod, including hardness, wear resistance, low-friction behaviour, and corrosion resistance, have a direct influence on system performance. In particular, micro-wear occurring at the rod–seal interface may lead to stick-slip behavior, seal degradation, and reduced service life. In this study, C35 steel specimens were subjected to ferritic nitrocarburizing followed by post-oxidation (FNC + ONC) at a constant treatment temperature with different ammonia diffusion times. The nitriding treatments were performed at 570 °C for 2.45, 4.30, and 6.30 h. After treatment, the specimens were characterized by Vickers microhardness measurements, optical microscopy, and neutral salt spray corrosion tests. Surface hardness and compound (white) layer thickness were comparatively evaluated. The experimental results revealed that the optimum ammonia diffusion time under the investigated processing conditions was 4.30 h at 570 °C, resulting in an average surface hardness of 576 HV, a compound layer thickness of 18.3 μm, and a corrosion resistance of 168 h according to ISO 9227. Furthermore, increasing the ammonia diffusion time led to higher surface hardness and a thicker compound layer. These findings demonstrate that appropriate control of the ammonia diffusion time significantly enhances the surface performance of gas-nitrided C35 steel while maintaining a compound layer suitable for gas spring applications.

Keywords : Gas Nitriding; C35 Steel; Gas Spring; Ferritic Nitrocarburizing; Surface Hardness; Compound Layer;

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