SwRI will be exhibiting at the ASNT Annual Conference, Booth No. 659.
Join us for the following presentation:
"X-ray Computed Tomography and Destructive Examination of Titanium and Stainless Steel Joined with Inertial Welding," Keith Bartels
SwRI is building a mass spectrometer (MASPEX™) for use on the NASA/JPL mission to Europa currently scheduled for launch in 2024. One component of MASPEX utilizes inertial welding to join 12.7-mm-diameter cylinders of Titanium 6AL-4V (Ti) and 316L stainless steel (SS). For quality control, the welded pieces were imaged using cone-beam X-ray computed tomography (CT). The parts were imaged with a tube voltage of 200 kV and three-dimensional images with a resolution of 24 μm were obtained. A total of 24 weld samples were imaged. Examination of the Ti-SS interface showed intrusions of SS into the Ti side of that part as well as intrusions of Ti into the SS side of the part. These intrusions were observed to a varying degree in all 24 of the welds examined. Representative welded parts were destructively analyzed by metallographic examination and scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS). A longitudinal examination of the weld interface revealed the intrusions to exhibit intermixing between the Ti and SS alloying elements. Elemental mapping by EDS demonstrated preferential segregation of the chromium (Cr) from the SS within the intermixed zones. EDS line scan measurements across a discrete intrusion demonstrated a gradual decrease in Ti, aluminum (Al), and vanadium (V), and an increase in iron (Fe), Cr, and nickel (Ni). Discrete intrusions exhibited dimensions on the order of 50 to 400 μm. Intrusions on the order of 350 μm or greater could be correlated between SEM and CT analyses.