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The cold spray materials deposition process has been investigated for manufacturing oxide dispersion-strengthened (ODS) steel fuel cladding tubes. Gas-atomized 14YWT ODS steel powder was used as the feedstock material. A parametric investigation of the cold spray process involving substrate materials of various hardnesses, gas preheat temperatures, and carrier gas compositions was performed to achieve the highest quality deposit. The high-velocity impact of the powder on the substrate led to dissolution of discrete oxide nanoparticles, which subsequently reprecipitated during postdeposition annealing at high temperatures. The tubes were manufactured by deposition on an Al-alloy mandrel substrate and subsequent chemical dissolution of the substrate. A 204-mm-long and 1-mm-thick ODS steel cladding tube was successfully manufactured. The grain growth and distribution of oxide nanoparticles in ferritic steel matrix were identified at elevated temperatures. Overall, the cold spray process holds considerable promise for rapid, cost-effective manufacturing of ODS steel cladding tubes.

In this paper, we present a novel approach to the approximate solution of elliptic partial differential equations on compact submanifolds of $\mathbb {R}^{d}$ , particularly compact surfaces and the surface equation ${\Delta }_{\mathbb {M}} u - \lambda u=f$ . In the course of this, we reconsider differential operators on such submanifolds to deduce suitable penalty based functionals. These functionals are based on the residual of the equation in an integral representation, extended by a penalty on the first-order normal derivative. The general framework we develop is accompanied by error analysis and exemplified by numerical examples employing tensor product B-splines.

Energy minimization is one of the properties that make univariate splines so favorable in many problems of approximation and estimation; interpolation in and extrapolation from sparse data sites and smoothing of noisy data in particular. In this paper, we present a novel approach to approximate energy minimization on certain classes of submanifolds that gives rise to new methods for extrapolation and smoothing on submanifolds. To accomplish this, we minimize intrinsic functionals approximately by minimising a suitable extrinsic formulation of the functional augmented by a penalty on the first order normal derivative. The general framework we develop is accompanied by error analysis and exemplified by tensor product B-splines.

Annealing of attrition-milled, electrolytically produced chromium powder has been investigated to improve cold spray coating deposition efficiency of pure chromium on Zr-alloy substrate for light water reactors with the goal of enhancing high-temperature oxidation resistance. The annealing heat treatment at 800 °C for 5 h induced microstructural transitions in the powder such as the development of equiaxed grains and strain relaxation, both associated with a measured decrease in nano-hardness. Deposition efficiency of the annealed powder was about three times more than the as-received electrolytic Cr powder. In addition, the utilization of the annealed powder reduced substrate deformation effects. A qualitative explanation of the effects powder microstructure on the cold spray deposition process in terms of the resulting coating microstructures and deposition efficiencies has been introduced. Finally, high-temperature exposure tests indicated that oxidation resistance of these Cr coatings was comparable to that previously reported for those produced using gas-atomized Cr powder. This study suggests that annealing of electrolytic Cr powder is a practical and economically favorable pathway to produce oxidation-resistant cold spray Cr coatings. More generally, use of the widely available electrolytic and mechanically milled powder vastly opens scope of cold spray deposition process, where atomized powders may not be either available or challenging to produce.

The cold spray coating process has been developed at the University of Wisconsin-Madison for the deposition of oxidation-resistant coatings on zirconium alloy light water reactor fuel cladding with the goal of improving accident tolerance during loss of coolant scenarios. Coatings of metallic (Cr), alloy (FeCrAl), and ceramic (Ti2AlC) materials were successfully deposited on zirconium alloy flats and cladding tube sections by optimizing the powder size, gas preheat temperature, pressure and composition, and other process parameters. The coatings were dense and exhibited excellent adhesion to the substrate. Evaluation of the samples after high-temperature oxidation tests at temperatures up to 1300°C showed that the cold spray coatings significantly mitigate oxidation kinetics because of the formation of thin passive oxide layers on the surface. The results of the study indicate that the cold spray coating process is a viable near-term option for developing accident-tolerant zirconium alloy fuel cladding.