In order to obtain tungsten with great surface qualities and high polishing efficiency, a novel method of chemical enhanced shear dilatancy polishing (C-SDP) was proposed. The effects of pH values and H2O2 concentrations on the polishing performance of tungsten C-SDP were studied. In addition, the corrosion behaviors of tungsten in solutions with different pH values and H2O2 concentrations were analyzed by electrochemical experiments, and the valence states of elements on the tungsten surface were analyzed by XPS. The results showed that both pH values and H2O2 concentrations had significant effects on tungsten C-SDP. With the pH values increasing from 7 to 12, the MRR increased from 6.69 µm/h to 13.67 µm/h. The optimal surface quality was obtained at pH = 9, the surface roughness (Ra) reached 2.35 nm, and the corresponding MRR was 9.71 µm/h. The MRR increased from 9.71 µm/h to 34.95 µm/h with the H2O2 concentrations increasing from 0 to 2 vol.%. When the concentration of H2O2 was 1 vol.%, the Ra of tungsten reached the lowest value, which was 1.87 nm, and the MRR was 26.46 µm/h. This reveals that C-SDP technology is a novel ultra-precision machining method that can achieve great surface qualities and polishing efficiency of tungsten.

The strain rate-related creep-fatigue (CF) interactions on the long-term service damage of 9%Cr steel-welded joint were investigated at low-strain amplitude (0.2%). Initially, the average CF life gradually increased from 1,103 to 2,185 cycles as strain rate increased from 0.0001 to 0.002 s À1 , and then it slowly decreased from 2,185 to 1,503 cycles as continuously increase the strain rate from 0.002 to 0.005 s À1 . By increasing strain rates, the microscale observation indicates the CF fracture location could be shifted from the fine-grained heataffected zone (FGHAZ) to the base metal (BM) region. Meanwhile, the local microscale mechanical properties including hardness, elastic modulus, creep resistance, and strain rate sensitivity on the fractured specimens with a series of strain rates were detected by instrumental nanoindentation. With increasing CF strain rates, the nanoindentation hardness and creep resistance evidently dropped. Based on the characteristics of microstructural evolution and the variation in local mechanical properties, strain rate effects of CF interaction on fracture mechanism of the welds were systematically discussed.

To investigate the surface damage of a material by He ions, a dispersion-strengthened W-1wt%TiC alloy was irradiated by 5-keV He ions at 773 K, 973 K, and 1173 K up to an ion dose of 1.8 × 10 21 He m −2 , respectively. No He bubble formation was observed under transmission electron microscopy at any temperature for He doses less than 1.5 × 10 20 He m −2. When this dose was exceeded, He bubbles grew and void swelling increased with increasing irradiation doses. Naturally, the growth of He bubbles and the void swelling became more pronounced with increasing irradiation temperatures. Compared to the published data on commercially available pure W, the formation of He bubbles was suppressed by TiC particles in the W-TiC alloy, especially at low doses.

In this study, in order to improve and restore the performance of the polishing pads and reduce the cost of chemical mechanical polishing, three types of material polishing pads, namely, polyurethane, damping cloth, and non-woven fabric, were selected for the experiment. Accordingly, each polishing pad was set up with diamond conditioner and high-pressure micro-jet (HPMJ) conditioning control experiments. Subsequently, the fluctuation ranges of the material removal rate on the three polishing pads were 2.73–3.75 μm/h, 1.38–1.99 μm/h, and 2.36–4.32 μm/h, respectively under the HPMJ conditioning method, while the fluctuation ranges of the material removal rate on the three polishing pads were 1.80–4.14 μm/h, 1.02–2.09 μm/h, and 1.78–5.88 μm/h under the diamond conditioning method. Comparing the polishing pad morphologies under SEM, we observed that the surface of the polishing pad after HPMJ conditioning was relatively clean, and the hole structure was not blocked. Contrastingly, there remained numerous abrasive particles on the surface after the conventional diamond conditioning and the hole structure was blocked. Thus, the HPMJ conditioning technology is better than the traditional diamond conditioning technology. Subsequently, the polishing pad after HPMJ conditioning has a longer service life and a more stable material removal rate than that after traditional diamond conditioning.