Wear study of additively manufactured 316L stainless steel gears

Laser powder bed fusion (LPBF), also as known as selective laser melting (SLM), is considered one of the most representative techniques in laser additive manufacturing (AM) because of its high manufacturing accuracy and flexibility in manufacturing geometrically complex components. However, despite the well-established use of LPBF technology for 316L stainless steel (SS), there is limited research on the tribological behaviour of finished products in real-world applications. This study aims to understand the degradation process and wear mechanism of LPBF-made 316L SS gears in comparison to gears made using a conventional manufacturing technique. The gear samples used in this study were printed using 316L SS powder and LPBF technique. These gears were tested in a lubricated condition on a single-stage gearbox rig. Oil samples and gear moulds were collected during the experiments. A laser scanning microscope was used to image the gear moulds so that the surface features of the gears could be studied, allowing for an understanding of the degradation process and quantitative analysis of the surface evolution. The wear depths of the tested gears were measured using a real-time technique, namely absolute transmission error (TE), and were confirmed by analysing changes in the tooth profile using the mould images. Wear debris was collected at different operating times to examine the wear mechanisms involved in the tests. The results of the LPBF SS gears reveal that the gears underwent a smoothening phase due to the initial rough surface finish, followed by surface pitting. The data collected from the tests on the LPBF SS gears were compared with those of traditional S45C steel gears tested under the same operating conditions. The wear mechanisms of both the conventional and the LPBF-made SS gears are very similar; both experienced an initial running-in stage where the manufactured gear surfaces were smoothened before a surface pitting process began. Additionally, it was found that the SS gears manufactured using the LPBF method without surface treatment had a higher wear rate than the conventional steel gears. This study provides valuable evidence of the surface degradation process of LPBF-made SS gears. Understanding this process is important for developing potential strategies to improve product performance and lifespan when using LPBF technology to manufacture mechanical parts.