Effect of different working conditions on tribological behaviors of PcBN/440c stainless steel in vacuum environment

Polycrystalline cubic boron nitride (PcBN) is a widely used tool material for cutting hard materials under high-speed and heavy-duty cutting conditions. As the need for in-orbit manufacturing and service in vacuum environment of outer space grows, understanding the tribological behavior of PcBN tools during vacuum operation becomes increasingly important. This study investigates the effect of different working conditions on the tribological behavior of PcBN discs and high‑carbon chromium alloy steel (440c) balls in vacuum. The tribological behavior of tribopair is analyzed. The experimental results reveal that the average of coefficient of the friction (CoF) is generally lower at 100 r/min than at 300 r/min and decrease with increasing load at two different speeds. The CoF of the 300 r/min group exhibits greater ups and downs at different load cases. The wear rate increases and then decreases with increasing load at different speeds. These fluctuations in CoF and wear rate are attributed to the transformation of the wear form and the effect of frictional heat build-up. Based on the SEM and EDX results, the wear mechanism is predominated by abrasive wear, gradually transitioning to adhesive wear with increasing loads. These findings provide insights into the tribological behavior of PcBN composite materials in vacuum. The results aim to inform the development of more efficient and dependable PcBN tools for in-orbit manufacturing and service applications.