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Directed energy deposition (DED) additive manufacturing process has been attractive to the fabrications of FeCrAl alloys due to the advantage of near net shaping of complex shaped components. In order to improve the strength, TiC particles strengthened FeCrAl alloys have been fabricated by DED using blended FeCrAl powder and TiC nanoparticles. The results show that the TiC particles in the DED alloys have submicron sizes, and polygonal or dendritic shapes. Most TiC particles are distributed along the dendritic/grain boundaries. The additions of TiC particles effectively refine the grain sizes, and at the same time prompt a columnar to equiaxed transition of grains. The grain sizes are reduced from 1377 μm to 47 μm, 21 μm and 22 μm when the TiC particle contents in the DED alloys increase from 0 wt% to 0.7 wt%, 2.4 wt% and 3.5 wt%, respectively. The room temperature strength of the FeCrAl alloys increase with the increase of TiC particle content. With 3.5 wt% TiC particle content, the FeCrAl alloy has good mechanical properties with yield strength of 437 MPa, ultimate tensile strength of 688 MPa, and an elongation of 19 %. The 650 ℃ high temperature strength of the FeCrAl alloys first decrease and then increase with the increase of TiC particle content. With 3.5 wt% TiC particle content, the FeCrAl alloy has excellent mechanical properties with yield strength of 208 MPa, ultimate tensile strength of 223 MPa, and an elongation of 53 %. The present study provides an important basis for fabricating high strength particle-strengthened FeCrAl alloys using the DED process.

The oxide dispersion strengthened ferritic steel with a nominal composition of Fe–14Cr–2W–0.5Ti–0.06Si–0.2V–0.1Mn–0.05Ta–0.03C–0.3Y2O3 (14Cr–ODS) was fabricated by sol–gel method in combination with hydrogen reduction, mechanical alloying (MA) and hot isostatic pressing (HIP) techniques. Pure Fe–1.5Y2O3 precursor was obtained by a sol–gel process and a reduction process at 650 °C for 3 h and pure 14Cr–ODS alloy powders were obtained from this precursor and the alloying metallic powders by mechanical alloying. The microstructure analysis investigated by transmission electron microscopy (TEM) and energy dispersive spectrometry (EDS) reveal that Y–Ti–O complexes and V–Ti–O complexes with a main particle size of 8 nm are formed in the 14Cr–ODS steel matrix. After HIP sintering the weight and the relative density of the compacted ingots are about 0.8 kg and 99.7%. The uniform elongation and ultimate tensile strength of the ODS steel obtained by HIP after annealing at 1100 °C for 5 h are about 13% and 840 MPa, respectively.

Tungsten carbide coatings were fabricated on tungsten substrates with spark plasma sintering method by covering a layer of graphite powders on the substrates. Composition, crystalline structure, hardness, thermal conductivity and corrosion resistance of the coatings were evaluated by scanning electron microscopy, X-ray diffraction, Vickers hardness test, electrochemical impedance spectroscopy and dipping experiment. It was found that the W–C coated samples exhibit three-layer structure containing three different phases, which from the surface to the interior are hexagonal WC, hexagonal W 2 C and body center cubic W(C), respectively. Thickness of the total W–C coatings is about 20 μm, and closely dependent upon the holding time and sintering temperature; average hardness of the coatings was 2125 HV; thermal conductivity of both uncoated and coated samples is similar and decreases from 180 to 130 W m −1 K −1 in the temperature range of 27–500 °C. Furthermore, W–C coated samples have better corrosion resistance than that of uncoated samples in 3.5% NaCl solution or 10% nitric acid solution at room temperature.

Dense W, W–1 wt%La2O3 and W–1 wt%Y2O3 samples with fine microstructure were fabricated by microwave sintering method using nano-scaled powders. The FESEM and TEM analysis, thermal conductivity and Vickers micro-hardness measurements were exploited to characterize these samples. It is found that the addition of Y2O3 and La2O3 nano-particles could significantly hinder the grain growth of tungsten in the consolidation process, decreasing the average grain size from 3.2 μm in pure W down to 0.7 μm in W–1%Y2O3 sample. The thermal conductivity and relative density of these samples are higher than 120 W/m K and in the range of 95–97%, respectively. The Vickers hardness of W–1%Y2O3 sample reaches as high as 6.91 GPa, 30% higher than that of pure W (5.04 GPa).