Characteristics of tribo-oxidation surface evolution in molybdenum–tungsten–vanadium hot-work die steel

High-temperature wear tests on molybdenum–tungsten–vanadium steel were conducted using a universal mechanical high-temperature friction and wear testing machine. The experimental results reveal the evolutionary mechanism of high-temperature friction in the oxide layer of the steel. The oxidation wear of the test steel occurred at 700 °C with the evolution of characteristic monolayer tribo-oxidation layers on the frictional surface. The frictional oxide underwent oxide initiation - lateral growth of massive oxide - formation of frictional oxide layer - local intrusion of oxide layer into substrate - local penetration of oxide lateral growth contact. The frictional oxide evolutionary process was accompanied by a shedding of the frictional oxide surface. Carbides in the test steel prevented the tribo-oxidation layer from invading the matrix. The unique evolutionary characteristics of the tribo-oxidation layer are essential factors affecting the mechanism of maintaining slight oxidative wear.