Ten percent Cr steels are considered to be prospective materials for the production of pipes, tubes, and blades in coal-fired power plants, which are able to operate within ultra-supercritical steam ...parameters. The microstructural evolution of a Re-containing 10% Cr-3Co-3W steel with low N and high B content during creep was investigated at different strains at 923 K and under an applied stress of 120 MPa using TEM and EBSD analyses. The studied steel had been previously normalized at 1323 K and tempered at 1043 K for 3 h. In the initial state, the tempered martensite lath structure with high dislocation density was stabilized by M23C6 carbides, NbX carbonitrides, and M6C carbides. At the end of the primary creep stage, the main microstructural change was found to be the precipitation of the fine Laves phase particles along the boundaries of the prior austenite grains, packets, blocks, and martensitic laths. The remarkable microstructural degradation processes, such as the significant growth of martensitic laths, the reduction in dislocation density within the lath interiors, and the growth of the grain boundary Laves phase particles, occurred during the steady-state and tertiary creep stages. Moreover, during the steady-state creep stage, the precipitation of the V-rich phase was revealed. Softening was in accordance with the dramatic reduction in hardness during the transition from the primary creep stage to the steady-state creep stage. The reasons for the softening were considered to be due to the change in the strengthening mechanisms and the interactions of the grain boundary M23C6 carbides and Laves phase with the low-angle boundaries of the martensitic laths and free dislocations.
Two Josephson voltage standard (JVS) systems operated at the National Institute of Standards and Technology (NIST) and Lockheed Martin Astronautics (LMA) were compared by using four traveling Zener ...standards. A Measurement Assurance Program (MAP) protocol was adopted for the comparison. The Zener data were first corrected based on their pressure coefficients to compensate for the pressure difference due to the lab elevations and local meteorological conditions. The Welch-Satterthwaite formula and effective degrees of freedom (DOF) were then used to calculate the expanded uncertainty. The mean difference between the measurements of the two laboratories was found to be 0.059 /spl mu/V with an expanded uncertainty of /spl plusmn/0.189 /spl mu/V at the 95% confidence level.
