Diamond grits reinforced coating on 35CrMnSi coal shearer cutting teeth: Microstructure, wear resistance and service performance in coal extraction

Abstract

Coal shearer cutting teeth is a key components in coal mining, its service life is very important for the productivity and cost in coal mining. In order to improve the wear resistance and service life of 35CrMnSi coal shearer cutting teeth in coal mining, diamond grits reinforced coating was vacuum cladded on 35CrMnSi steel by using Ni–Cr based alloy as a binder. Furthermore, post-heat treatment was performed to eliminate the negative influence of high cladding temperature on the properties of 35CrMnSi steel. The microstructure, phase composition, mechanical properties, reciprocating sliding wear properties, and coal mining application of the coated cutting teeth were investigated. The results show that the coating of about 360 μm thickness is primarily composed of randomly distributed diamond grits that are partially fastened by the Ni–Cr based cladded alloy and metallurgically bonded to the 35CrMnSi steel. Besides, some Cr–C precipitates (Cr3C2, Cr7C3, Cr23C6) and CrB precipitates are formed, which can enhance the coating together with the diamond grits. The hardness of 35CrMnSi steel(3.15Gpa) decreases by 10% after cladding(2.18Gpa) but increases by twofold after the post-heat treatment(6.36Gpa). The wear weight losses of the original 35CrMnSi steel, the coating after cladding, and the coating after post-heat treatment are 9.24 mg, 0.49 mg, and 0.12 mg, respectively. The wear rate calculation indicates that the wear resistance of diamond grits reinforced coating before and after post-heat treatment is about 90 times higher than that of uncoated 35CrMnSi steel. The wear mechanism of the coating is mainly abrasive wear, breaking of diamond grits, and plowing of the grits to the Al2O3 ball. The industrial tests demonstrate that the service life of 35CrMnSi cutting teeth with diamond grits reinforced coating can be increased by 1.6 times. Moreover, the coating can effectively eliminate sparks generated by high-speed friction. Therefore, diamond grits reinforced coating can significantly improve the service life and production efficiency of the coal shearer cutting teeth.