Beitrag zur Zerspanung intermetallischer γ-Titanaluminide durch Bohren, Gewindebohren und Fräsen

Bergmann, S.

The intermetallic compound γ-Titanium-Aluminide possesses excellent material characteristics which make it suitable for use in aviation turbines, internal combustion engines and other industrial applications. However, machining of this material is very challenging owing to a combination of high brittleness, low thermal conductivity and high hot strength. Rapid tool wear results due to thermal softening of the cutting material and adhesion wear. This thesis contains the findings of experimental investigations on drilling, tapping and milling of γ-Titanium-Aluminide. The aim is to machine a connecting rod for a high-speed internal combustion engine. Hitherto, only very little scientific research on these machining processes has been carried out.

Starting with an introduction on titanium aluminide alloys, this thesis has been divided into three main parts: drilling, tapping and milling. To determine suitable tool concepts the cutting material, rake angle and tool coating was varied. A domain of suitable machining parameters has been identified by analyzing cutting speed, depth of cut, feed and lubrication concept. The feasibility of these different processes is characterized mainly by tool wear, process forces and workpiece surface integrity. The surface integrity is of special importance regarding micro cracks owing to the material brittleness. They can be easily generated and may lead to early component failure.

The results reveal that coated fine-grained cemented carbide tools, with neutral or negative rake angles, are suitable. High feed rates or cutting depths lead to excessive mechanical loads and tool life decreases accordingly. The use of oil as cutting fluid reduces adhesion wear and thereby contributes to an economical machining process via increased tool life. The results achieved within this research work can be successfully applied in selecting appropriate cutting tools and parameters for an optimal process design.

Published as

Dissertation Technische Universität Dortmund, Vulkan Verlag, Essen, 2009, ISBN 978-3-8027-8746-1