Electrochemical methods to detect susceptibility of Ni-Cr-Mo-W alloy 22 to intergranular corrosion

Alloy 22 (UNS N06022), a Ni-Cr-Mo-W based alloy, is a candidate material for the outer wall of nuclear waste package (NWP) containers. Even though the alloy is highly stable at low temperatures, it could undergo microstructural changes during processing such as welding and stress relieving. Formation of topologically close-packed (TCP) phases such as μ, P, σ, etc. and Cr-rich carbides could make the material susceptible to localized corrosion. Hence, it is important to correlate the microstructural changes with the corrosion resistance of the alloy by nondestructive and rapid electrochemical tests. In this investigation, different electrochemical test solutions were used to quantify the microstructural changes associated with aging and welding of the wrought alloy 22. The results of double-loop (DL) electrochemical potentiodynamic reactivation (EPR) tests in 1 M H₂SO₄+0.5 M NaCl+0.01 M KSCN solution indicated Cr depletion during initial stages of aging of wrought alloy 22. Results of EPR tests in 2 M HCl+0.01 M KSCN solution at 60 °C correlated well with the Mo depletion that occurred near TCP phases formed during aging of both weld and wrought alloy 22 materials. The EPR test results were compared with standard chemical weight loss measurements specified by ASTM standard G-28 methods A and B.     

The great networking correction: frames reaffirmed

The paper considers how frame-based network technologies of local area networks are retaking their role as the primary campus technology, providing connections from desktop through backbone. This development comes at the expense of cell-based ATM, which was widely viewed as the inevitable, and highly desirable, next wave in transport technologies. ATM had been expected to supplant LAN-based transport and allow data, voice, and video to converge on a single, multi-transmission rate network. That ATM will become the dominant campus transport technology, however, seems less and less likely. Technical benefits once unique to ATM have become fewer with recent advances in both Ethernet and token ring technologies. As a result, monetary investment in ATM technology has fallen off sharply. ATM technology will likely become less visible as fewer servers and high-end workstations use it for direct connections. It will, of course, continue to provide robust switch-to-switch connections in some campus backbones. It may thrive in the carrier space, where its scalability, support for multiple traffic types, and circuit-based paradigm can be put to good use