Experimental Investigation on the Wear Characteristics of a Novel TBM Cutter Ring Material with High Hardness and High Toughness under Different Rock Conditions

The wear resistance of TBM cutter ring material not only depends on its own microstructure and mechanical properties, but also closely related to the type of rock and wear load. Under different wear conditions, the wear mechanism of experimental steel with different mechanical properties is quite different, which leads to great changes in the wear resistance. TBM cutter ring material belongs to high alloy martensitic steel, its microstructure is composed of tempered martensite and carbide. The carbide with high hardness can ensure good wear resistance, while the hardness and impact toughness of TBM cutter ring steel can be adjusted effectively by tempered martensite. The tempering temperature and holding time is the main means to adjust the characteristics of tempered martensite. In this paper, five kinds of experimental steels with varying hardness and impact toughness gradient were prepared by different tempering treatment. The variation rules of wear resistance of experimental steels with different properties were studied under different wear loads and different rock types, and the wear morphologies of the wear surface and subsurface were observed and analyzed by scanning electron microscopy. The evolution of wear mechanism of experimental steels with different properties under different wear conditions was revealed. Specifically, the wear behavior of cutter ring steel with different mechanical properties under different types of rocks in real production process was simulated. The results showed that under the wear condition of sandstone, the wear mechanism of test steel with different mechanical properties was microscopic cutting. With the increase of hardness, the mass loss of specimens decreased, and the wear debris changed from strip to sawdust. The greater the wear load, the higher the wear mass loss of the test steel. Under the wear condition of granite, the wear mechanism of each test steel was mainly micro-ploughing and the wear resistance was positively correlated with hardness when the wear load was lower than 3 000 N, and no crack appeared on the worn surface of each test steel. Meanwhile, the wear debris were powdery or block. When the load increased to 5000 N, crack gradually occured on the worn surface of experimental steel with the increase of hardness. For the cutter ring steel with toughness higher than 8 J, the wear mechanism was mainly micro-ploughing. When the toughness of the test steel was lower than 7 J, cracks appeared the worn surface, which resulted in a sharp weakening of the wear resistance of test steel. Therefore, when the load was higher then 3 000 N, the wear resistance of the experimental steel depended on both hardness and toughness, and the experimental steel with good hardness and toughness had better wear resistance. The research on the wear behavior of cutter ring steel with different mechanical properties under different rock types provided a theoretical basis for the selection of cutter ring properties in practical application.