دانلود رایگان مقاله انگلیسی خصوصیات اصطکاکی و پوشیده از آلیاژ دیرگداز بر پایه کریستال نیکل در دمای بالا - اشپرینگر 2018

Abstract

The purpose of this study was to investigate the friction and wear behavior of single crystal superalloys at elevated temperatures. Pin-on-plate experiments were conducted using a custom-built high-temperature fretting/wear apparatus. Measurements were performed on two single crystal Ni-based alloys and Waspaloy® (used as a baseline material). The coefcient of friction for the single crystal materials (i.e., during running-in and steady state) was lower compared to the Waspaloy®. In addition, the experiments showed that the friction coefcient of the single crystal is dependent on the crystallographic plane; the friction coefcient was lower for the tests on the {100} plane compared to the {111} plane. The wear behavior was aligned with the friction behavior, where the single crystal Ni-based alloys showed slightly higher wear resistance compared to the Waspaloy®. Ex situ analysis by means of FIB/SEM and XPS analysis revealed the formation of Co-base metal oxide layer on the surface of the single crystal alloy. Similarly, a Co-base oxide layer is observed on the counterface providing a self-mated oxide-on-oxide contact and thus lower friction and wear compared to the Waspaloy.

4  Conclusion

In this study, the friction and wear behavior of single crystal superalloys were investigated at elevated temperatures. Pin-on-plate experiments were performed on conventionally heat-treated single crystal, coarse γ′ single crystal and Waspaloy® plates using a conventionally heat-treated single crystal for all experiments. In addition, ex situ analysis by means of FIB/SEM and XPS analysis was performed in order to capture the underlying mechanisms leading to the friction and wear behavior of the diferent alloys. The coefcient of friction for the single crystal materials (i.e., during running-in and steady state) was lower compared to the Waspaloy®. The experiments showed that the friction coefcient of the single crystal is dependent on the crystallographic plane; the friction coefcient was higher for the tests on the {100} plane compared to the {111} plane. The wear behavior was similar to the friction results, where the conventionally heat-treated single crystal showed higher wear resistance compared to the Waspaloy®. However, the coarse γ′ single crystal showed the highest wear, which is attributed to the lower hardness compared to the other alloys tested in this study. Ex situ analysis by means of FIB/SEM and XPS analysis revealed the formation of Co-based metal oxide layer on the surface of the single crystal. Similarly, a Co-based oxide layer is observed on the counterface providing a self-mated oxide-on-oxide contact and thus lower friction and wear compared to the Waspaloy.