WC对铜基和镍基喷焊覆层材料耐气蚀性能的影响

在 Cu Ni Si B、 Ni Cr Si B自熔合金粉末中添加 WC陶瓷颗粒 ,利用氧乙炔焰粉末喷焊工艺制备覆层材料。用超声波振动气蚀仪对覆层材料进行耐气蚀性能研究 ,用扫描电子显微镜对覆层材料表面气蚀破坏形貌进行观察。结果表明 :复合覆层材料的耐气蚀能力比基体强 ;提高 Cu Ni Si B覆层材料耐气蚀能力的途径是强化晶界。

Effect of sintering atmosphere on corrosion resistance of Ni/(NiFe_2O_4-10NiO) cermet inert anode for aluminum electrolysis

A comparative study on the corrosion resistance of 17Ni/（NiFe2O4-10NiO） cermet inert anode prepared in differentsintering atmospheres was conducted in Na3AlF6-Al2O3 melt. The results indicate that the corrosion rates of NiFe2O4-based cermetanodes prepared in the vacuum and the atmosphere with oxygen content of 2×10^-3 （volume fraction） are 6.46 and 2.71 cm/a,respectively. Though there is a transition layer with lots of holes or pores, a densified layer is formed on the surface of anode due tosome reactions producing aluminates. For the anode prepared in the atmosphere with oxygen content of 2×10^-3, the thickness of thedensification layer （about 50 μm） is thicker than that （about 30 μm） formed on the surface of anode prepared in the vacuum. Thecontents of NiO and Fe（II） in NiFe2xO4-y-z increase with the decrease of oxygen content in sintering atmosphere, which reduces thecorrosion resistance of the material.

High Temperature Corrosion of Water Wall Materials T23 and T24 in Simulated Furnace Atmospheres

Candidate materials for water wall of supercritical and ultra-supercritical utility boilers,T23 and T24,were chosen as the experimental samples and exposed to oxidizing atmosphere,reducing atmosphere and oxidizing/reducing alternating atmosphere separately.The corrosion temperature was 450-550?C.The effects of oxygen con-tent and temperature on the corrosion in reducing atmosphere and alternating atmosphere were investigated.The scanning electron microscope(SEM) and energy dispersive spectrometer(EDS) were used to examine the corroded samples.The results show that the corrosion kinetics of T23 and T24 can be described by the double logarithmic equation and parabolic equation respectively.To describe the corrosion of materials accurately it is not sufficient to analyze the macro-mass gain and the macro-thickness of the corroded layer only,but the EDS should be applied to examine the migration depth of corrosive elements O and S.It is revealed that the corrosion becomes more severe when H2S is present in the corrosive gas.S is more active than O,and Cr can reduce the migration of oxygen but not S.The combination corrosion of S and O and pure [S] has a stronger corrodibility than pure H2S.T24 suffers the most severe corrosion at oxygen content of 0.8%.Corrosion is aggravated when the corrosion temperature is above 450 ℃ in the alternating atmosphere.T23 has better corrosion resistance than T24 and W contributes a lot to the corrosion resistance of T23.

Electrochemical evaluation of zinc and magnesium alloy coatings deposited on electrogalvanized steel by PVD

Zinc alloy coating attracted much attention due to its high anti-corrosive properties.Particularly,zinc alloy coatings containing magnesium was considered a promising metallic alloy due to a remarkable improvement of corrosion resistance.The proper magnesium content for Zn-Mg alloy coatings was studied.The samples were prepared using thermal evaporation method.The influence of Zn-Mg alloy coating on corrosion resistance was evaluated using immersion test,potentiodynamic test,and galvanic test in 3% NaCl solution at room temperature.The results show that the corrosion resistance of Zn-Mg alloy coatings is strongly dependent on magnesium content.Corrosion potential decreases with increasing magnesium content,whereas current density increases up to 15% magnesium content,and passivity region was found only in Zn-Mg coatings.

Corrosion Resistance of Valve Steels in Combustion Gases from Gasoline and Propane-Butane

The corrosion resistances of widely used X33CrNiMnN23-8, X50CrMnNiNbN21-9, X53CrMnNiN20-8 and X55CrMnNiN20-8 high-alloyed austenite valves steels in combustion engines have been compared. The comparison was performed on the basis of results of kinetic corrosion of the test steels in combustion gases from gasoline with 5% ethanol additive （v/v） and the combustion gases from propane-butane. The corrosion test was performed gravimetrically under thermal shock conditions by heating samples of the test steels from room temperature up to 1,173 K in exhaust gases from a combustion engine, and holding them at this temperature for 2 h and then cooling at room temperature for about 25 min. Then the same thermal shock was repeated and after every 10 to 20 such cycles the mass of the specimens was measured. This experiment simulated the working conditions of a highly thermal loaded exhaust valve in a spark ignited engine. The analysis performed shows that the corrosion resistances of X33CrNiMnN23-8 and X50CrMnNiNbN21-9 valve steels in an environment of combustion gases from propane-butane and in gases from gasoline with 5% ethanol additive （v/v） are comparable, whereas the corrosion resistance of X53CrMnNiN20-8 and X55CrMnNiN20-8 valve steels in an environment of combustion gases from propane-butane is slightly worse than in gases from gasoline with 5% ethanol additive （v/v）.