Observation And Analysis To Boundary Layer Behavior In Powder Lubrication Interface Of Sheet Metal Forming

Metal plastic forming technology is widely used, but the contact pressure and temperature on plastic forming interfacial is high. The traditional oil and grease lubrication cannot meet the requirements.Considering the good applicability of powder lubrication to extreme conditions, we use friction test device combined with a variety of analytical techniques to study the mechanism of powder lubrication in sheet metal forming.First, according to test design, a series of sheet metal forming tests were performed based on powder lubrication. Friction coefficient and the three dimensional surface microstructure and surface morphology of boundary layer and metal surface were analyzed by changing the contact pressure, speed, powder layer thickness and the original surface roughness. Experimental results show that, it is favorable for the formation of powder layer to increase the amount of powder, the contact pressure and the velocity appropriately. The increase in the thickness of the powder cannot exceed a certain critical value; the optimum thickness varies with the use conditions. Despite that rough surface is more suitable for storing powder, but it is not conducive to the adhesion of the powder, so it is difficult to form complete powder layer.Secondly, considering about the damage factor of powder boundary layer, the main factors causing vertical scratches crawling phenomenon and the main factors causing lateral scratches transfer film were studied; we also studied the typical form of powder layer destruction. There are some results. In low speed or high load condition, the crawling phenomenon is more evident; To increase the thickness of the powder layer can reduce the crawling phenomenon; The main damage form of boundary layer are scratch, brittle shedding, delamination, adhesion and bulge. The typical damage form of boundary layer varied with working conditions.