Bin Han,Shigen Zhu,Weiwei Dong,Yunfeng Bai,Hao Ding,Yilan Luo,Ping Di
In this study, 85-xWC-xTiC-15wt%Al 2 O 3 (x = 0, 5, 10 and 20 wt%) composites were fabricated via hot pressing sintering technology. The influences of TiC additives on the mechanical performance and electrochemical behavior of WC-Al 2 O 3 composite in NaCl solution were investigated. The mean size of WC grain showed a downward trend with the increase of TiC content. The relative density, hardness and fracture toughness of WC-based composites were improved by TiC additives. The maximum values of mechanical performance were obtained when TiC content was 10 wt%. Moreover, the research results indicated that TiC additives significantly increase the corrosion potential and decrease the corrosion current density in NaCl solution. When TiC content increased, the charge-change resistance (R ct ) value presented an uptrend, and then decreased obviously when the TiC content reached 20 wt%. The XPS spectrum and SEM images proved that TiO 2 passivation film was formed on the surface of WA15-10TiC composite. Therefore, it could be concluded that TiO 2 passive film could inhibit further corrosion of the composite.
Bin Han,Shigen Zhu,Weiwei Dong,Yunfeng Bai,Hao Ding,Yilan Luo,Ping Di
(85-x)WC–15 wt%Al 2 O 3 –xTiC (x = 0, 1.5, 2.5, 5, 10, and 20 wt%) composites were prepared by vacuum hot-press sintering. The influence of TiC addition on the corrosion behaviour of WC–Al 2 O 3 composites in 0.1 M NaOH solution was revealed. The results suggest that all the samples containing added TiC had the TiC phase and (W, Ti) C solid-solution phase, while the base composite had neither phase. With increasing added TiC content, the average grain size of WC decreased, and the relative density first increased and then decreased. Furthermore, the results suggest that the addition of TiC could noticeably increase the free corrosion potential and impedance and reduce the corrosion current density. However, the composite containing 20 wt% added TiC showed the opposite trend. Therefore, it can be concluded that the corrosion performance of the composites in an alkaline medium can be improved by adding an appropriate amount of TiC. The change in corrosion properties was caused by changes in the solid-solution phase, relative density, and TiO 2 oxide film .
Hu Weiqiang,Gong Fengming,Liu Shaocun,Tan Jing,Chen Songhua,Wang Hui,Ma Zongqing
The oxide dispersion strengthened Mo alloys (ODS-Mo) prepared by traditional ball milling and subsequent sintering technique generally possess comparatively coarse Mo grains and large oxide particles at Mo grain boundaries (GBs), which obviously suppress the corresponding strengthening effect of oxide addition. In this work, the Y 2 O 3 and TiC particles were simultaneously doped into Mo alloys using ball-milling and subsequent low temperature sintering. Accompanied by TiC addition, the Mo−Y 2 O 3 grains are sharply refined from 3.12 to 1.36 µm. In particular, Y 2 O 3 and TiC can form smaller Y−Ti−O−C quaternary phase particles (∼230 nm) at Mo GBs compared to single Y 2 O 3 particles (∼120 nm), so as to these new formed Y−Ti−O−C particles can more effectively pin and hinder GBs movement. In addition to Y−Ti−O−C particles at GBs, Y 2 O 3 , TiO x , and TiC x nanoparticles (<100 nm) also exist within Mo grains, which is significantly different from traditional ODS-Mo. The appearance of TiO x phase indicates that some active Ti within TiC can adsorb oxygen impurities of Mo matrix to form a new strengthening phase, thus strengthening and purifying Mo matrix. Furthermore, the pure Mo, Mo−Y 2 O 3 , and Mo−Y 2 O 3 −TiC alloys have similar relative densities (97.4%–98.0%). More importantly, the Mo−Y 2 O 3 −TiC alloys exhibit higher hardness (HV 0.2 (425 ± 25)) compared to Mo−Y 2 O 3 alloys (HV 0.2 (370 ± 25)). This work could provide a relevant strategy for the preparation of ultrafine Mo alloys by facile ball-milling.
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