This study manufactured a SiC coating layer using the vacuum kinetic spray process and investigated its microstructure and wear properties. SiC powder feedstock with a angular shape and average particle size of 37.4 μm was used to manufacture an SiC coating layer at room temperature in two different process conditions (with different degrees of vacuum). The thickness of the manufactured coating layers were approximately 82.4 μm and 129.4 μm, forming a very thick coating layers. The SiC coating layers consisted of α-SiC and β-SiC phases, which are identical to the feedstock. Cross-sectional observation confirmed that the SiC coating layer formed a dense structure. In order to investigate the wear properties, ball crater tests were performed. The wear test results confirmed that the SiC coating layer with the best wear resistance achieved approximately 4.16 times greater wear resistance compared to the Zr alloy. This study observed the wear surface of the vacuum kinetic sprayed SiC coating layer and identified its wear mechanism. In addition, the potential applications of the SiC coating layer manufactured using the new process were also discussed.

Recently, attempts have been made to use porous metal as catalysts in a reactor for the hydrogen manufacturing process using steam methane reforming (SMR). This study manufactured Ni-Cr-Al based powder porous metal, stacked cubic form porous blocks, and investigated high temperature random stack creep property. To establish an environment similar to the actual situation, a random stack jig with a 1-inch diameter and height of 75 mm was used. The porous metal used for this study had an average pore size of ~1161 μm by rolling direction. The relative density of the powder porous metal was measured as 6.72%. A compression test performed at 1073K identified that the powder porous metal had high temperature (800°C) compressive strength of 0.76 MPa. A 800°C random stack creep test at 0.38 MPa measured a steady-state creep rate of 8.58×10–10 s–1, confirming outstanding high temperature creep properties. Compared to a single cubic powder porous metal with an identical stress ratio, this is a 1,000-times lower (better) steady-state creep rate. Based on the findings above, the reason of difference in creep properties between a single creep test and random stack creep test was discussed.

MoO3 thick film was manufactured by using a thermal spray process (Atmospheric Plasma Spray, or APS) and its microstructure, phase composition and properties of the coating layer were investigated. Initial powder feedstock was composed of an orthorhombic α-MoO3 phase, and the average powder particle size was 6.7 μm. As a result of the APS coating process, a MoO3 coating layer with a thickness of about 90 μm was obtained. Phase transformation occurred during the process, and the coating layer consisted of not only α-MoO3 but also β-MoO3, MoO2. Phase transformation could be due to the rapid cooling that occurred during the process. The properties of the coating layer were evaluated using a nano indentation test. Hardness and reduced modulus were obtained as 0.47 GPa and 1.4 GPa, respectively. Based on the above results, the possibility of manufacturing a MoO3 thick coating layer using thermal spray is presented.

Co-Cr-Mo based sheet I-WP lattice was fabricated via laser powder bed fusion. The effect of microstructure and the I-WP shape on compressive mechanical response was investigated. Results of compression test showed that yield strength of the sheet I-WP was 176.3 MPa and that of bulk Co-Cr-Mo (reference material) was 810.4 MPa. By applying Gibson-Ashby analytical model, the yield strength of the lattice was reversely estimated from that of the bulk specimen. The calculated strength of the lattice obtained was 150.7 MPa. The shape of deformed lattice showed collective failure mode, and its microstructure showed that strain-induced martensitic transformation occurred in the overall lattice. The deformation behavior of additively manufactured sheet I-WP lattice was also discussed.

This study investigated the effect of heat treatment on the microstructure and impact toughness property of AISI D2 manufactured with direct energy deposition (DED) and compared the results with conventional wrought material. The fracture crack propagation behavior was examined in connection with microstructures through fracture surface analysis. AISI D2 manufactured with DED had a eutectic structure that turned into a net-type carbide after heat treatment, and Cr-rich needle-type secondary carbide was observed. Impact toughness of DED AISI D2 measured 2.0 J/cm2 in the as-built sample and 1.1 J/cm2 in the heat-treated sample. Compared to a wrought heat-treated AISI D2, DED AISI D2 had relatively low impact toughness. DED AISI D2 and wrought material had different crack propagation mechanisms. In DED AISI D2, the eutectic structure and net-type carbide boundary were identified as the major microstructural factor decreasing impact toughness.

An open-cell Ni-Mo-Cr foam was newly manufactured using electrostatic powder spraying process and its room-temperature compressive properties were investigated in this study. For manufacturing Ni-Mo-Cr foam, Ni-Mo-Cr powders were sprayed on the polyurethane pre-form by electrostatic powder spraying process. And then, Ni-Mo-Cr powder sprayed pre-forms were sintered at 1200℃, 1250℃, and 1300℃, respectively. The relative densities of Ni-Mo-Cr foams were measured at 4 ~ 5%. Room temperature compressive curves of ESP Ni-Mo-Cr foams represented the typical compressive 3-stages (elastic, plateau, densification) of open-cell metallic foam. As a result of observation of deformed specimen, the fracture mode found to be changed from brittle to ductile as sintering temperature increased. Based on these findings, correlations between structural characteristics, microstructure, and compressive deformation behavior were also discussed.