ZrMoN films were deposited on a 304 stainless-steel (SS304) substrate with a radio-frequency (RF) reactive magnetron-sputtering system and the properties were changed by adjusting the power of the Mo target. The corrosion behaviors of the ZrMoN films were investigated with potentiodynamic tests and electrochemical impedance spectroscopy (EIS) under the condition of an aerated 0.5M H2SO4 + 1,99 mg/L NaF solution at 70°C. The results revealed that all samples with ZrMoN films have good hydrophobicity. The XRD test showed that the ZrMoN film is the substitutional solid solution of Mo atoms into ZrN films. As an overall evaluation, the power of the Mo target is 30W. A coated sample displays the best corrosion resistance in the cathode of the PEMFC environment when the power of the Mo target is considered, which indicates that with an increase of the power of the Mo target, the solid solubility also increases; but with a continuous increase of the Mo-target power, the solubility increases and a lattice distortion also occurs, leading to an increase in defects. Keywords: ZrMoN, corrosion behavior, bipolar-plate material, physical-vapor-deposition technology (PVD) ZrMoN prevleke so bile nane{ene na substrat 304 nerjavnega jekla (SS 304) z radiofrekven~nim reaktivnim (angl. RF) magnetronskim napr{evalnikom in lastnosti so bile spremenjene s prilagoditvijo mo~i Mo tar~e. Korozijsko obna{anje prevlek ZrMoN smo raziskovali s potenciodinamskimi preizkusi in elektrokemijsko impedan~no spektroskopijo (EIS) v raztopini 0,5 M H2SO4 + 1,99 mg/L NaF pri temperaturi 70°C. Rezultati so pokazali, da imajo vsi vzorci z ZrMoN prevlekami dobro hidrofobnost. XRD-analiza ka`e, da je prevleka ZrMoN nadomestna trdna raztopina atomov Mo v ZrN plasti. Rezultati ka`ejo najbolj{o korozijsko odpornost na katodi v okolju PEMFC pri mo~i Mo tar~e 30 W, kar ka`e, da se s pove~anjem mo~i Mo pove~uje tudi trdna topnost. Vendar pa se s kontinuiranim pove~evanjem mo~i Mo tar~e neprestano pove~uje tudi topnost, zato pride do popa~enja kristalne mre`e, kar povzro~i pove~anje napak. Klju~ne besede: ZrMoN, korozijsko obna{anje, bipolarni material, tehnologija nana{anja iz parne faze (PVD)
Abstract:Bainitic bearing steel of GCr15Si1Mo has been selected as the testing material in this paper. The point rolling contact fatigue experiments are carried out under a well lubricated condition with/without oil lubrication condition. The steel with different volume fractions of carbide are tested. The surface morphology and the distribution of carbides in microstructure of the samples before and after rolling contact fatigue test are observed by scanning electron microscopy. The rolling fatigue properties of these specimens are determined by the Weibull plots. The results show that the rolling fatigue property of the specimen with 1.9 vol.% carbide is superior to the specimen of 5.1 vol.% carbide without lubrication condition. However the order of quality of rolling fatigue property under a well oil lubricated condition of the specimen, from best to the worst is:the specimen without carbide, the specimen with 5.1 vol.% carbide and with 1.9 vol.% carbide. The carbide is easy to be the rolling fatigue crack source as it is a hard phase in matrix of the steel. Then the specimen without carbide shows the best rolling fatigue property. The pits are formed on the surface of the sample after the carbides are fallen off, which increase the adhesive force between the lubricating oil and the surface of specimen. This is beneficial to increasing the oil film thickness during the process of test. Therefore, the rolling contact fatigue life of the specimen is improved.
Abstract:Rolling contact fatigue wear (RCFW) behavior of a new type carbide-free bainitic steel(CFBS) has been investigated by means of RCFW testing, scanning electron microscope, transmission electron microscopy and X-ray diffraction. The results show that the CFBS exists the satisfactory RCFW performance, the failure mode of fatigue wear of CFBS is shallow spalling. The severe plastic deformation layer produced on the specimen surface can effectively block the fatigue crack toward greater depth. The RCFW behavior is more excellent of the sample which is austenized at 920 ℃ for 40 min, and immediately austempered in a molten salt bath at a temperature of 350 ℃ for 30 min than that for 100 min. The RCFW life of the sample of 350 ℃ for 30 min can reach 8.0×10 6 cycles. Retained austenite can effectively improve the hardness of the contact surface and relax the stress concentration at the crack tip, and the RCFW behavior is improved. During the RCFW process, the hardness increase in the specimen surface and redistribution of the alloying elements exhibit a positive effect on the improvement of the RCFW behavior. Key words:carbide-free bainitic steel;rolling contact fatigue wear;retained austenite;alloying element 0 前言 1
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