Die Wall Lubrication vs. Bulk Lubrication: microstructure, mechanical properties and dimensional and geometrical precision of low alloyed steels

The paper presents the results of a project aiming at investigating the potentiality of Die Wall Lubrication (DWL) in powder compaction. A DWL system was developed and installed on a 200 T hydraulic press and specimens were produced to investigate mechanical properties, dimensional and geometrical precision after sintering at high temperature. DWL increases density, while the effect on pore size and morphology in the sintered parts is negligible. Tensile strength and elongation of the sintered specimens are noticeably increased with reference to specimens produced with Bulk Lubrication (BL), while the positive effect on the bending fatigue resistance is less pronounced. Tooth root fatigue resistance of low pressure carburized gears is 71% of that of wrought 20MnCr5 carburized gears. Dimensional and geometrical precision of the parts produced with DWL is very good, comparable if not better than that typical of the parts produced with BL..