Abstract: The graphite-nickel coatings on the surface of Q345 steel plates were prepared by flame spraying to solve the mud-caking problems of shield tunneling. The friction behaviors of Q345 steel samples with and without graphite-nickel coatings against mudstone compacts were analyzed by friction-wear tests, and the influences of graphite-nickel coatings on the friction coefficient, wear loss, wear scars were systemically studied. The results show that, the dry-friction coefficients of Q345 steel samples with and without graphite-nickel coatings against mudstone compacts are 0.4 and 0.3, respectively, and the wet-friction coefficients are 0.25 and 0.05, respectively. As the load increasing from 50 to 500 g, the wear loss of samples with coating increases slowly under the wet friction condition; while it takes a step-change upward under the dry friction condition. Under the dry friction condition, both width and depth of wear scar increase as increasing the load, and the furrows occur locally. The in-situ testing proves that the flame sprayed graphite-nickel coatings on the end surfaces of disc cutter barrels can effectively inhibit the mud-caking phenomena during shield tunneling in mudstone layers.