Impact-sliding behavior of Ni-based coating prepared on tunnel boring machine disc cutter material produced using a plasma transferred arc welding process

Abstract

The working condition of the disc cutter of the tunnel boring machine (TBM) is extremely harsh and is severely worn during the rock-cutting and tunneling process. Reducing the wear rate of the cutter and extending the service life of the cutter are essential to improving the economic costs and safety of the TBM. This article explores the feasibility and effectiveness of using surface coatings to improve the wear resistance of the cutter ring. NiCrBSi/WC coatings with different current intensities were prepared on the disc surface using plasma surfacing technology. The wear performance of the coating was evaluated using a bespoke impact-sliding device that fits the actual working conditions, and the wear mechanism was studied in detail. According to the “tadpole-like” wear scar characteristics of the coating after the impact-sliding wear experiment, the wear scar zone can be divided into two regions: the impact region and the sliding region, which are consistent with the actual wear characteristics of the cutter ring. In addition, the wear behavior of the coating noticeably changed under each experiment parameter, and the evolution process of the impact-sliding wear of the gage cutter at each position can be well reproduced. When the impact angle was 45°, the wear depth and wear volume of the coating were significantly smaller than those of the uncoated samples. This is mainly due to the metallurgical bond between the Ni-based alloy zone (binder phase) and the spherical WC particles (hard phase) on the surface of each specimen. When impacted by the tribo-ball, the WC particles can undergo plastic deformation and relaxation through the Ni-based alloy zone under the applied force, thereby obtaining excellent impact and sliding resistance. When the impact angle was 60°, the impact dominates, causing the impact force to increase. Furthermore, compared with the uncoated specimens, the wear depth and wear volume of the coated specimens significantly increased, indicating that the anti-impact ability was seriously degraded in such situation. In summary, the powder composition and preparation process parameters should be reasonably selected according to the impact angle, and the impact-sliding wear experiment can effectively evaluate the impact and sliding wear performance of different coatings. This approach has an important directive function in the promotion and application of cutter ring coatings.