PNNL

Abstract

The HFIR JP26 irradiation experiment contained a series of transmission electron microscopy (TEM) disks intended to study helium effects in ferritic/martensitic steels [1,2]. Table 1 lists specimens from that experiment chosen for examination. The Eurofer-97 disks were prepared with thin NiAl coatings so that irradiation would produce He by transmutation of the Ni and deposit that He uniformly in a thin layer ~6 to 8 µm thick adjacent to the coating. Yamamoto et al [3] give details of the specimen design and preparation. Following irradiation, samples were prepared for TEM using a cross-section technique to show He effects in the implanted layer near the NiAl coating. The procedure involved mounting the TEM disk between two half cylinders of Cu wire with thermal setting epoxy and slicing the composite wire using a slow speed saw equipped with a diamond-impregnated blade to produce 3 mm disks, with the TEM slice supported between the half-cylinders of Cu. Each composite disk was then dimple ground to a central thickness of ~100 µm, and ion milled using a Gatan Precision Ion Polishing System. Ion milling was performed with 5 KV Ar ions to perforation so that the hole grew into the area of interest, followed by ion polishing at 2 KV for up to 1800 s to minimize Ar ion damage near the surface. Microstructural examinations were performed on a JEOL 2010F operating at 200 KeV in transmission with images recorded digitally.