The application of temper-etch inspection to micromilled AISI 4340 steel specimen

Micromachining has seen application growth in a variety of industries requiring a miniaturization of the machining process. Machining at the micro level generates different cutter/workpiece interactions, generating more localized temperature spikes in the part/sample, as suggested by multiple studies. Temper-etch inspection is a non-destructive test used to identify `grind burns' or localized over-heating in steel components. This research investigated the application of temper-etch inspection to micromachined steel. The tests were performed on AISI 4340 steel samples. Finding, indications of localized over-heating was the primary focus of the experiment. In addition, change in condition between the original and post-machining hardness in the machined slot bottom was investigated. The results revealed that, under the conditions of the experiment, no indications of localized over-heating were present. However, there was a change in hardness at the bottom of the machined slot compared to the rest of the sample. Further research is needed to test the applicability of temper-etch inspection to micromilled steel and to identify the source of the change in hardness.