Improvements in the machining of aero-engine alloys using self-propelled rotary tooling technique

• Published in: Journal of materials processing technology Vol. 185; no. 1; pp. 60 - 71
• Main Author: Ezugwu, E.O.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.04.2007
• Subjects: Abrasion and attrition wear mechanisms; Chipping and fatigue wear; Higher metal removal rates; Improved surface finish; Low flank wear rate; Machinability; Nickel alloy; Rotary cutting; Round inserts; Titanium alloy; Titanium alloy; Round inserts; Higher metal removal rates; Improved surface finish; Low flank wear rate; Machinability; Abrasion and attrition wear mechanisms; Rotary cutting; Chipping and fatigue wear; Nickel alloy
• ISSN: 0924-0136
• DOI: 10.1016/j.jmatprotec.2006.03.112

Approximately two-thirds of all the superalloys produced are consumed by the aerospace industry for the manufacture of jet engines and associated components, mainly in the hot end of aircraft engines and land-based turbines. The remaining third of superalloy consumption is used by the chemical, medical and structural industries in applications requiring high temperature properties and/or exceptional corrosion resistance. Ability to retain high mechanical and chemical properties at elevated temperatures make superalloys ideal materials for use in both rotating and stationary components in the hot end of jet engines. These materials as well as structural ceramic and hardened steels pose formidable challenges for cutting tool materials during machining, hence they are referred to as difficult-to-cut. The basic difference between rotary cutting and conventional cutting is the movement of the cutting edge in addition to the main cutting and feed motions. Self-propelled rotary tools (SPRT) employs round inserts rotating continuously about its axis as a result of the driving motion impacted by the cutting force, thus minimising the effect of thermal energy along the entire edge and preventing excessive heating of a particular portion of the insert edge. Major benefits provided by SPRT include several hundred-fold increase in tool life, lower cutting temperature, higher metal removal rate, generation of fine surface finishes due to the circular cutting edge and improved machinability of difficult-to-cut materials such as nickel and titanium base alloys. Extremely low rate of flank wear can be obtained when machining aerospace superalloys, particularly titanium alloys, even at higher speed conditions with very negligible or no effect on the machined surfaces. This paper will provide an overview of developments in rotary tools, the principles of rotary cutting, structure and design of SPRT, factors influencing rotary tool life and detail information of practical machining data as well as analysis of tool failure modes and tool wear mechanisms in comparison to conventional (fixed tool) machining technique.