Drills with a curved cutting edge and radius on the periphery were shown to have superior performance when drilling Inconel 718 compared to drills with either a straight or concave cutting edge and sharp periphery (up to three times the number holes drilled). The hole integrity obtained when drilling Inconel 718 was not sufficient to meet the standards required by the aerospace industry. Drilled holes contained significant workpiece smearing which appeared as a white layer in the microstructure. Smearing is not acceptable in the aerospace industry because it can cover up potentially catastrophic surface defects such as cracks. The use of reaming and mill boring produced holes with lower surface roughness, minimal microstructural deformation and the white layer produced by the drilling operation had been removed. In particular the mill bore technique gave very low surface roughness values down to 0.046 micrometer Ra compared to approximately 0.178 micrometer Ra for reaming. The milling tools used were standard commercially available solid carbide end mills and with the use of circular interploitation the same milling tool can be used for many different hole sizes and shapes giving further cost savings and productivity increases compared to reaming (reduced tool changes, less tooling inventory). Future work will focus on improving the stability in mill boring as the tool enters cut and achieving the same dimensional tolerance that can be obtained with reaming.
Tool life and surface integrity aspects when drilling and hole making in Inconel 718
Journal of Materials Processing Technology ; 200 , 1-3 ; 424-432
2008
9 Seiten, 11 Bilder, 1 Tabelle, 28 Quellen
Article (Journal)
English
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