Experimental Investigation of Endogenous Lubrication during Cold Upsetting of Sintered Powder Metallurgical Components

Abstract

Lubrication is essential in metal forming processes. As an example, it has a significant effect on the extent of homogeneity of forming and the resulting component surface. Thus, an adequate lubrication technique is required for a consistent part quality. In this contribution a new lubrication approach for cold bulk metal forming is presented. By exploiting the process-related porosity of powder metallurgical (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 omission of the additional lubrication step, and an increased deformability due to compensation of lubricating film break are expected. Besides that, the porosity of the PM component is reduced leading to improved mechanical properties. Experimental investigations with cylindrical PM components were carried out by compression tests in dependence of initial porosity, impregnation time and lubricant. It was found that the required maximum load is reduced by up to 39 % by applying the new lubrication method. In addition, relative densities up to 99 % are reached after deformation.

Influence of Dwell Time and Pressure on SPS Process with Titanium Aluminides

“…In order to quantify the influence of dwell time and holding pressure on the compaction and the resulting microstructure, the relative density was first determined. For this, the actual density of the sintered part was calculated by measuring weight and volume (or rather diameter and height) and was then divided by the full density, according to the manufacturer, which is 3.97 g/cm 3 for GE48 and 4.15 g/cm 3 for TNM [14]. Afterwards, the evaluation was carried out based on Vickers hardness measurements and microstructural analyses in the positions shown in Figures 1 and A1 Right.…”

Investigations on the consolidation of TNM powder by admixing different elemental powders

“…The density of the compact was calculated by measuring weight as well as diameter and height. Then, the density was divided by the referential full density, which is 4.15 g/cm³ for TNM according to the manufacturer [15].In order, to characterise the overall bond quality between the powder particles, the tensile splitting strength was determined in accordance with DIN EN 12390-6:2010-09 [16]. The sample was placed on a flat metal plate and loaded radially with a test specimen in the form of a cylindrical pin until failure.…”