This paper presents a tribological investigation of austenitic steel 21-4N exhaust valve material, dry sliding against ductile cast iron GGG-40 seat material, at a temperature of 500°C, to study the effect of increasing loads on tribofilm formation and retention at the contact interface. The effect of these tribofilms, on the friction and wear behaviour of the tribo-pair, is highlighted. High temperature reciprocating pin-on-disc tests were performed on a tribometer at loads of 20 N to 50 N with a constant stroke of 2 mm and an oscillating frequency of 20 Hz. A distinct running-in behaviour is observed at loads up to 40 N with the coefficient of friction attaining a very low and stable level with increase in sliding time. The average Coefficient of Friction ranges between 0.12 and 0.15. Optical/Scanning Electron Microscope micrographs and Energy Dispersive Spectroscopy analysis indicate the creation of compact and durable tribofilms at loads up to 40 N. At the highest load of 50 N, the Coefficient of Friction behaviour is slightly different. With a low value at the beginning, it shows an increasing trend and reaches a peak around the 10-min mark and reduces thereafter. At this load, despite indications of higher abrasive wear, the Coefficient of Friction behaviour, Optical/Scanning Electron Microscope micrographs and Energy Dispersive Spectroscopy analysis indicate evidence of early deterioration and subsequent reformation of the tribofilms with increase in sliding time. The seat material exhibited comparatively more wear than the valve material; however, the wear coefficients lie in the mild wear regime for the tribo-pair. The results of this investigation indicate the compatibility of the tribo-pair and suggest its use in the exhaust valve/seat application.

中文翻译：

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增加载荷的干滑动条件下摩擦膜形成和保持的摩擦学研究

本文介绍了奥氏体钢 21-4N 排气阀材料的摩擦学研究，在 500°C 的温度下干滑动球墨铸铁 GGG-40 阀座材料，以研究增加载荷对摩擦膜形成和保留的影响。联系界面。强调了这些摩擦膜对摩擦副的摩擦和磨损行为的影响。在摩擦计上以 20 N 至 50 N 的载荷、2 mm 的恒定行程和 20 Hz 的振荡频率在摩擦计上进行高温往复销钉盘试验。在高达 40 N 的负载下观察到明显的磨合行为，随着滑动时间的增加，摩擦系数达到非常低且稳定的水平。平均摩擦系数介于 0.12 和 0.15 之间。光学/扫描电子显微镜显微照片和能量色散光谱分析表明，在高达 40 N 的负载下会产生紧凑耐用的摩擦膜。在 50 N 的最高负载下，摩擦系数行为略有不同。开始时值较低，呈上升趋势，并在 10 分钟附近达到峰值，此后下降。在此负载下，尽管有较高的磨料磨损迹象，但摩擦系数行为、光学/扫描电子显微镜显微照片和能量色散光谱分析表明，随着滑动时间的增加，摩擦膜早期退化和随后重新形成的证据。阀座材料比阀门材料表现出更多的磨损；然而，磨损系数位于摩擦副的轻度磨损状态。