Abstract: Lubrication is crucial in hot forming processing to reduce forming force, improving workpiece surface quality and boost material utilization. TZM alloy (Titanium-Zirconium-Molybdenum alloy), with excellent high-temperature mechanical properties, has been explored as a mold material for vacuum isothermal forging. However, research on its lubricating materials is still lacking. Especially compared with the atmospheric environment, the effects of vacuum (non-oxidizing environment) and surface roughness on the high-temperature lubricating properties of glass lubricants remain unknown, which has limited the efficiency and workpiece quality of vacuum isothermal forging. To address this, this work designed and prepared a novel glass lubricant capable of providing effective lubrication at 950 ℃. By investigating the high-temperature interactions between glass and TZM alloy under different atmospheres (air or nitrogen), surface roughness conditions of the pin and dry friction, the lubrication mechanism of the glass lubricant was explored. Results showed that the glass lubricant exhibited superior lubricating performance in a nitrogen atmosphere with a smoother pin (friction coefficient=0.066 at 950 ℃). This was mainly because, in oxygen-containing environments, MoO₃ formed from matrix oxidation could attack the glass, inducing the formation of molybdates and causing the glass lubricant layer to fail. In contrast, in a nitrogen atmosphere, using a rougher pin leaded to the loss of antioxidant function in the lubricant film and sodium deficiency in the friction layer, making the residual glass layer difficult to shear (friction coefficient=0.31). This work offered guidance for using TZM alloy as a mold material in the vacuum isothermal forging process and the design of lubricants for hot metal forming processes.