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Abstract. In this work, the effect of the quenching media (brine, water, and two types of naphthenic mineral oils) and the tempering temperature (200, 400, 600 ∘C) on the static mechanical properties and the fatigue life has been investigated using 300 fatigue and 36 static tension tests. S–N curves and standard deviations of fatigue life under each heat treatment condition were calculated and shown. The fracture surfaces of the selected 11 specimens were observed by the scanning electron microscope and the reasons of affecting the fatigue life were discussed. To estimate the mean fatigue life under the conditions of any given tempering temperature and cycle stress amplitude based on 300 fatigue tests, the mean fatigue life estimation method based on RBF neural network was presented and verified by 12 other fatigue tests. The test results have shown that (1) the mean fatigue life decreases with the increase of tempering temperature for the same quenching media, (2) the mean fatigue life using brine is more than water which is more than naphthenic mineral oils for the same tempering temperature, and (3) the proposed method based on RBF neural network could accurately estimate the mean fatigue life when the tempering temperature and cyclic stress amplitude are given for each quenching medium.

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Silicon carbide (SiC) is a promising material for fabricating wire compacting dies due to its advantages of light weight and even high wear resistance over the tungsten carbide, which currently is the most popular material used to produce compacting dies. In present study, a layer of CVD diamond film is deposited on the interior-hole surface of compacting dies using the hot filament chemical vapor deposition (HFCVD) method, following by a surface polish process, aiming at further elongating the lifetime of compacting dies and improving the surface quality of produced wires. The characterization of both as-deposited and polished CVD diamond films is employed by scanning electron microscopy (SEM), surface profiler, Raman spectroscopy and X-ray diffraction (XRD) spectroscopy. Furthermore, the performance of as-fabricated CVD diamond coated compacting dies is examined in the real production process. The results exhibit that the as-deposited CVD diamond films are homogeneous and their surface finish is significantly smoothened after the surface polish process. As compared with the conventional compacting dies, the working lifetime of the diamond coated SiC compacting dies can be increased by a factor of above 15 and in the course of processing, copper stranded wires with high surface quality and uniform sectional area can be obtained.