Diffusion bonding is a key manufacturing process for nucleation applications including compact heat exchangers. Accurately predicting the alloy's behavior during the diffusion bonding process presents challenges, primarily due to the intricate interplay of microstructural evolution and physical processes such as compressive loading, temperature history, and component migration. The current study develops a phase-field model designed to simulate the diffusion bonding in 316H stainless steel, a material with exceptional high-temperature strength, corrosion resistance and suitability to high-pressure conditions. Our model incorporates a multi-phase, multi-component framework that aligns the experimental observations with the grain growth and heterogeneous nucleation, where arbitrary external compressive load and temperature history are considered. The simulations focus on grain nucleation, growth, and microstructure evolutions across diffusion bonding line under a variety of temperature profiles, mechanical loads, and surface roughness conditions, mirroring experimental setups. Our model predicts consistent simulation results with experiments in terms of the grain size and distribution near the bonding area, offering a better understanding of the diffusion bonding mechanism and the manufacturing process for building reliable compact heat exchangers.

This study assesses the potential of scandia-stabilized zirconia (ScSZ) produced by very low-pressure plasma spraying (VLPPS) for metal-supported solid oxide fuel cell (MS-SOFC) applications. To investigate the microstructure of ScSZ, coating samples were deposited at spraying distances of 150, 250, 350 mm. The fragile nature of coating cross-sections suggests that the typical lamellar structure of zirconia is replaced by a transgranular structure. Nonetheless, apparent porosity, ionic conductivity, open circuit voltage, and ohmic resistance measurements indicate that VLPPS is a viable method for producing MS-SOFCs.

High manufacturing costs and long-term degradation are the main problems that have become a “bottleneck” and impeded SOFC’s further development. It is well known that a high operating temperature is the major cause that leads to these problems. As such, reducing the operating temperature becomes a hotspot of research. It has been reported that a uniform and dense coating can be prepared by using very low pressure plasma spraying (VLPPS) technology. The current study focuses on VLPPS for application in large-area (~100 × 100 mm) porous metal supported solid oxide fuel cell (MSSOFC), especially for the preparation of the electrolyte. It was found that the densification of the electrolyte was very good, as confirmed by the open-circuit voltage (OCV) of the cell. In the temperature range of 550~750°C, the OCV of the cell stabilized between 1.05 V and 1.1 V. The power density of the cell was also measured.

The fatigue crack propagation thresholds of SAW weld metal of 25Cr2Ni2MoV simulating product of fossil and nuclear power low pressure turbine rotor at different stress ratios are tested. There is a big dispersity of the test results, even at the same stress ratio. The double logarithm curves of the fatigue crack growth rate and stress intensity factor range are researched. The difference of critical points between stable propagation region and near-threshold region in different specimens is found to be an important cause to the dispersity. Their locations in the specimens can be determined by the method of backward inference. After the observation of the microstructures around the critical points, a good correspondence between the size of prior austenite grain and the maximum size of monotonic plastic zone on the crack tip is confirmed. The difference of the critical points at the same stress ratio is caused by the inhomogeneous microstructures. So the inhomogeneous microstructures in the multi-pass and multi-layer weld metal contribute to the dispersity of the experimental threshold values.