This study focused on the fatigue and corrosion fatigue of maraging steel 18Ni (250). The 18Ni (250) samples were tested for axial fatigue in air and 3.5% NaCl solution. The effects of loading frequency and stress ratio on the fatigue strength of 18Ni (250) were studied. In air, the loading frequency was 10 Hz, and the stress ratio was 0.5. However, three loading methods were used in the 3.5% NaCl solution: (i) the loading frequency of 1 Hz and stress ratio of 0.5; (ii) the loading frequency of 1 Hz and stress ratio 0.1, and (iii) the loading frequency 5 Hz and stress ratio 0.5. The corrosion fatigue strength of samples in the 3.5% NaCl solution was 63.3% lower than that of the samples in air. The fractures in the samples were observed after the test.
A new extraction process suitable for treating refractory CuCo2S4 under atmospheric pressure acidic leaching conditions was investigated. The effect of variables such as oxidant species, liquid-to-solid ratio, leaching time, oxidizing agent and mineral quality ratio, H2SO4 concentration, temperature and sodium chloride concentration on the extraction efficiency of Co, Cu and Fe from CuCo2S4 were investigated. Under optimal conditions including P80-P90 of the sample was d < 0.0074 mm, stirring speed of 400 rpm, leaching time of 8 h with sodium chlorate (NaClO3) and mineral quality ratio of 0.5, 2 mol/L H2SO4, liquid-to-solid ratio of 7, leaching temperature of 90°C and 4 mol/L sodium chloride. The leaching efficiency of Co, Cu, and Fe were nearly 97.08%, 100%, and 92.45%, respectively. Furthermore, the contents of cobalt and copper in leaching residue were all less than 0.4 wt.%, which satisfies the requirements of industrial production.