Gerald J. Tennenhouse

The effects of oxygen on the wear of Si3N4 against cast iron and steel

Abstract Oxygen is shown to be a factor in the wear of silicon nitride against cast iron and steel. Pin-on-disk tests show that the wear of silicon nitride against cast iron and steel is reduced when the oxygen concentration of the atmosphere is reduced. A relationship between pin-on-disk and machining tests is shown. Machining data are presented to indicate how the wear of the silicon nitride tool is reduced when the oxygen concentration at the toolworkpiece interface is reduced with a stream of nitrogen.

Method and apparatus for increasing wear life of ceramic tools

An apparatus and method are disclosed for reducing the oxygen concentration at the interface between a cutting tool and a relatively rotating metal workpiece. The apparatus comprises (a) a supporting means for holding the cutting tool in a predetermined position relative to the workpiece, and (b) means effective to direct a plurality of discrete flows of inert gas between the cutting tool and workpiece in a manner to substantially reduce the oxygen concentration in the zone to a predetermined level. The method comprises (a) directing a first stream of inert gas closely adjacent the interface, and (b) directing a second stream of inert gas to at least partially surround the first stream.

CANDIDATE MATERIALS FOR THE POSITIVE CURRENT COLLECTOR IN SODIUM-SULFUR CELLS - I. CERAMIC OXIDES

Abstract Chromium oxides doped with various metal oxides and strontium doped lanthanum chromite perovskites were prepared, physically characterized and tested for their suitability as coating materials for positive current collectors in sodium-sulfur cells. All of the materials studied are corrosion resistant. Perovskites show the highest conductivities, whereas only the chromium oxides doped with lower valence metal cations indicated acceptably low resistivities. However, upon exposure to the melt the resistivity of all materials studied increased in time. This has been shown to be caused by the loss of electron hole carriers during sample equilibration with the low oxygen partial pressure in the melt. The rate of the loss of conductivity is sufficiently slow to make the perovskites and chromium oxides doped with lithia or magnesia usable as coating materials for positive current collectors in sodium-sulfur cells.

The effects of oxygen on the wear of tungsten-carbide-based materials

Abstract Pin-on-disk wear tests have shown that oxygen is a factor in the wear of commercial tungsten-carbide-based tool materials against cast iron and steel under a variety of conditions. Tool posts were constructed that allowed nitrogen jets to be directed at a tool-workpiece interface during machining operations. A relationship was observed between pin-on-disk and machining tests and it was shown that the wear of tungsten-carbide-based tool inserts could be reduced by reducing the oxygen concentration of the atmosphere at the tool-workpiece interface with a flow of nitrogen.

Pin-On-Disk Wear Tests for Evaluating Ceramic Cutting Tool Materials

Pin-on-disk wear tests have shown that oxygen is a significant factor in the wear of both silicon nitride-and tungsten carbide-based tool materials against common iron-based alloys such as cast iron and steel. It was not expected that pin-on-disk wear tests could be related to tool wear in machining processes because the mechanical processes involved were different. However, it was found that if speeds, pressures, and environments were the same, there were surprisingly good correlations between the pin-on-disk tests and machining operations such as turning and boring.