Finish milling tests on wire-arc additive manufactured components made of a difficult-to-cut NiCrMo alloy (IN725) with subsequent analysis of the occurring cutting forces and resulting surface integrity via residual stress analysis
Source: BAM, division Testing Devices and Equipment
The acquisition as well as the processing of difficult-to-cut materials of highly stressed components is cost-intensive. Cost and resource efficiency efforts lead to more complex structures or contours, so that additive manufacturing steps for component repair and production offer significant economic advantages. At the same time, many applications require a high surface integrity. Subsequent machining of the additively manufactured components is mandatory in order to achieve the desired final contour or shape. On an industrial scale, this is usually done by machining with geometrically determined cutting edge. Surface integrity plays a central role for safety-relevant components. This is a complex interaction of topographic (defects, roughness), metallurgical (microstructural changes) and mechanical (residual stresses) influences. By using modern, hybrid machining processes (e.g., ultrasonic-assisted milling), it is possible to increase the surface integrity of the components. In this present work, finish milling tests were carried out on wire arc additive manufactured components made of a difficult-to-cut NiCrMo alloy (IN725) both with and without cooling lubricant and ultrasonic-assisted milling process was compared to conventional milling regarding the occurring cutting forces as well as the achieved surface integrity. It exhibits that ultrasonic assistance results in a significant reduction of the cutting forces. The superposition of the tool cutting action with the high-frequency oscillation in the rotation axis of the cutter leads to an increased surface integrity, especially when no cooling lubricant can be used during machining. This manifested itself in particular in a lower defect density, roughness and degradation of the surface layer of the finish-milled surfaces as well as in a lower residual stress state of the component
Surface finishing of hard-to-machine cladding alloys for highly stressed components
Dirk Schröpfer, K. Treutler, Andreas Börner, R. Gustus, Thomas Kannengießer, V. Wesling, W. Maus-Friedrichs
published in The International Journal of Advanced Manufacturing Technology, Vol. 114, issue 5-6, pages 1427 - 1442
BAM division Testing Devices and Equipment and division Weld Mechanics