Surface Integrity of Machined Structural Components

Book excerpt: A program has been run to evaluate the effects of different metal removal methods and variations of these methods on surface integrity. Three alloys were studied: beta rolled Ti-6Al-4V; AISI 4340, quenched and tempered, 50 Rc; and Inconel 718, solution treated and aged. Various grinding procedures caused the titanium alloy to exhibit a fatigue strength range of 13 to 62 ksi. The fatigue strength of 4340 due to grinding variables ranged from 62 to 102 ksi, while Inconel 718 showed a range of 24 to 60 ksi. Abusive grinding conditions always resulted in fatigue strengths at the minimum of these ranges. Milling variables exhibited a fatigue strength range of 32 to 72 ksi in the beta rolled titanium alloy. EDM and ECM on Inconel 718 yielded 22 and 39 ksi, respectively, compared to 60 ksi for gentle grinding. Guidelines for processing aerospace hardware considering surface integrity requirements are presented in the report.