Ecological lubrication in cold forming of sintered powder metallurgical components

Abstract

In this contribution a new lubrication approach for cold bulk metal forming is presented. By exploiting the process-related porosity of pm components as a lubricant storage, the resulting pressure of a forming process forces the stored oil to leak out lubricating the process. As a result advantages like a decrease of process time because of the lubrication step omission, and an increased deformability due to compensation of lubricating film break are expected. In addition, conversion coating, which have a negative environmental impact but are commonly used in cold bulk metal forming, can be avoided. Besides that, the porosity of the pm component is reduced leading to improved mechanical properties. Experimental investigations with cylindrical aluminium pm components were carried out by compression tests in de-pendence of initial porosity, impregnation time and lubricant. The oil saturation of all samples could be reached after 4400 min impregnation time. The relative density has an inversely proportional effect on the absolute and the relative impregnated oil quantity. The compression tests showed an increasing maximum load with decreasing oil quantity and rising relative density. Moreover, the loads determined in the reference tests tend to be greater in comparison to the novel lubrication method.