高Ni—Cr合金涂层防护锅炉受热面高温腐蚀的性能研究

针对电站锅炉受热面高温腐蚀的影响,采用电孤喷涂工艺,基体为锅炉受热面常用材料,喷涂国产高Ni—Cr合金涂层,对比FeCrAl涂层和T91材质,研究高温条件下的热腐蚀实验和热震实验,结合腐蚀动力学曲线与金相分析得到的孔隙率,说明国产高Ni—Cr合金在腐蚀防护上具有良好的性能,为今后电厂采用高Ni—Cr合金热喷涂涂层的防高温腐蚀应用提供借鉴．     

Ni-Cr alloy electrodepositing technology on Fe substrate and coating performance

The Ni-Cr alloy electrodepositing technology on iron substrate in the chlorid-sulfate solution and the impacts of main processing parameters on coating composition were studied. The optimal Ni-Cr alloy electrodepositing conditions are that the cathode current density is 16 A/dm^2, the plating solution temperature is 30 ℃ and the pH value is 2.5. The bright, compact coating gained under the optimal conditions has good cohesion and 24.1% Cr content. The results show that the coating is composed of crystalline, the average grain size is 82 nm and the higher the Cr content of coating, the larger the rigidity, and the higher the corrosion resistance. The rigidity of coating reaches 78.6（HR30T） and the passivation area broadens to 1.4 V when the Cr content of coating is 24.1%.     

三价铬超声-脉冲电沉积Ni-Cr/SiC纳米复合镀层

利用超声-脉冲复合电沉积法,在三价铬镀液体系中,添加羧酸盐-尿素配合剂和SiC纳米颗粒,制备了Ni-Cr/SiC纳米复合镀层。研究了超声-脉冲工艺参数对SiC纳米粒子复合量、铬含量以及镀层厚度的影响;利用电化学法分析了超声波对基质金属电沉积行为的影响。结果表明,超声-脉冲作用均有利于基质金属铬-镍的电沉积,从而提高镀层厚度及SiC与Cr的含量。利用SEM、XRD、和EDS分别对Ni-Cr/SiC纳米复合镀层的表面形貌、微观结构和相组成等进行表征。结果表明,采用该技术可制备厚度为21.2μm、SiC和Cr含量分别为3.8%和24.68%(质量分数)的Ni-Cr/SiC纳米复合镀层。磨损量和腐蚀曲线测试结果表明,SiC含量高的复合镀层,其耐磨性和耐蚀性更好。     

不同Cr含量的Ni-Cr合金熔覆层的高温氧化和热腐蚀特性

采用激光熔覆技术制备了Cr质量分数为10%、20%和40%的Ni-Cr合金熔覆层,研究了其在900 ℃下的高温氧化特性和600 ℃下Na₂SO₄+25% K₂SO₄混合盐中热腐蚀特性。结果表明,Cr含量对熔覆层的高温特性起着关键作用。提高Cr含量对提升熔覆层抗硫酸盐诱导的热腐蚀能力比提升抗循环高温氧化能力更有效。Cr40涂层抗高温氧化和热腐蚀性能最佳。Cr10的氧化产物以NiO为主,极易脱落,内部氧化严重。虽然Cr40表面可以形成单一的Cr₂O₃层,但热应力和生长应力引起的富Cr氧化物内部开裂,使Cr40的抗循环高温氧化能力仅略好于Cr20。面对热腐蚀时,Cr10表面呈现层状NiO和Ni₃S₂叠层分布的腐蚀产物,内部腐蚀区也生成了Ni的硫化物。Cr20表面Cr₂O₃层被破坏,内部腐蚀严重,生成了CrS。Cr40表面生成了致密的Cr₂O₃保护层,有效地防止了进一步腐蚀。     

718钢电火花沉积Ni-Cr合金涂层的组织特征及性能

利用电火花沉积技术,采用自制Ni-Cr合金电极在718模具钢表面制备了Ni-Cr合金涂层,分析了涂层的显微组织、硬度及耐磨性能.结果表明:涂层靠近基体的组织为细小的枝晶,而涂层中部及外层组织为超细晶粒;能谱分析显示,在涂层与基体界面处,Fe及Ni,Cr元素的含量发生突变;涂层的硬度由表层向基体方向呈梯度分布,最高可达8...     

电火花沉积Ni-Cr合金涂层的组织及性能

利用电火花沉积技术,采用自制电极在P20钢基材表面沉积Ni-Cr合金涂层,研究了沉积层的组织特征、显微硬度分布及耐磨、耐蚀性能.结果表明:通过优化沉积工艺参数可以获得厚度高达430μm的沉积层.电火花沉积层与基体的结合界面属于非均匀混合互熔结晶型界面,沉积层与基体呈现良好的冶金结合;涂层中下部组织为细小的枝晶组织,而上部组织为纳米晶结构.沉积层的硬度呈梯度分布,涂层外层硬度值最高.涂层的耐磨、耐蚀性能比基体有较大提高,涂层上部超细的纳米晶结构是其耐磨性能及耐蚀性能提高的主要因素.     

BN对镍基可磨耗密封材料烧结性能的影响

研究了BN含量对镍基可磨耗密封材料烧结性能的影响，分析了Ni-Cr和Ni-Cr／BN的烧结过程，并建立了烧结过程模型。结果表明：加入BN阻碍了粉末颗粒之间的烧结，引起材料烧结后体积膨胀和密度下降。     

Densities of molten Ni-（Cr,Co, W） superalloys

In order to obtain more accurate density for molten Ni-（Cr, Co, W） binary alloy, the densities of molten pure Ni and Ni-Cr, Ni-Co, Ni-W alloys were measured with a sessile drop method. It is found that the measured densities of molten pure Ni and Ni-Cr, Ni-Co, Ni-W alloys decrease with increasing temperature in the experimental temperature range. The density of alloys increases with increasing W and Co concentrations while it decreases with increasing Cr concentration in the alloy at 1 773-1 873 K. The molar volume of Ni-based alloys increases with increasing W concentration while it decreases with increasing Co concentration. The effect of Cr concentration on the molar volume of the alloy is little in the studied concentration range. The accommodation among atomic species was analyzed. The deviation of molar volume from ideal mixing shows an ideal mixing of Ni-（Cr, Co, W） binary alloys.     

固体润滑剂在Ni-Cr合金／Si3N4摩擦副界面的转移行为与摩擦学研究

考察了Ni-Cr-CaF2，Ni-Cr-PbO合金分别与Si3N4配副下的摩擦学性能，运用扫描电镜分析了固体润滑剂在Ni-Cr合金／Si3N4摩擦副界面的转移行为。结果表明，转移膜中CaF2的存在有利于在Si3N4陶瓷上形成有效的转移膜，但是CaF2未在摩擦界面优先转移，而软金属Pb与Si3N4陶瓷的润湿较差，不能存Si3N4陶瓷上形成软金属Pb的完整转移膜。     

The effect of particle size of alumina dispersions on the oxidation resistance of Ni-Cr alloys

The oxidation behavior of Ni-Cr alloys with various chromium concentrations and particle sizes of a dispersion of 10 vol.% Al₂O₃ was observed in 1 atm of oxygen at 1000°C. This study was intended to determine the critical chromium concentration to form a protective Cr₂O₃ oxide layer for different Al₂O₃ particle sizes. The oxidation rate of Ni-Cr alloys containing 10 vol.% Al₂O₃ followed a parabolic rate law and a Cr₂O₃ protective layer continuously formed when the oxidation rate decreased rapidly. Times to form a continuous and protective Cr₂O₃ layer during the initial oxidation shortened as the size of the dispersion decreased. The critical chromium concentration to form a protective Cr₂O₃ layer in the oxide scale was 69 wt.% and was related strongly to the particle size of the Al₂O₃ dispersion.