多种热源熔覆耐硫酸腐蚀合金工艺及组织性能的研究

发布时间：2018-05-18 15:05

本文选题：TIG熔覆 + 激光熔覆　；参考：《兰州理工大学》2017年硕士论文

【摘要】：硫酸生产及化工行业对耐高温浓硫酸阀门有大量需求。传统耐高温浓硫酸阀门大多由耐腐蚀合金铸造而成。由于高温浓硫酸具有较强的腐蚀性,使得符合性能要求的金属材料价格高昂,从而造成耐硫酸阀门的制造成本居高不下。为了得到符合技术要求同时价格低廉的阀门产品,应相关企业要求,本课题组提出分别使用TIG热源、激光热源和激光-电弧复合热源在价格相对较低的金属基体上熔覆一层耐腐蚀合金,在保持其原有性能的同时,降低耐腐蚀阀门的成本。相关企业对耐硫酸腐蚀设备的技术要求为:硬度HRC40,腐蚀速率0.1a/mm,耐腐蚀等级达到5级。首先,建立了热源系统试验平台,根据浙江宣达特种合金流程装备股份公司XDB-6耐腐蚀铸造合金的成分配方,研制出适合进行熔覆的耐腐蚀合金粉末。以304不锈钢为基体材料,分别使用TIG热源、激光热源和激光-电弧复合热源在基体表面熔覆耐腐蚀合金。分析了不同工艺参数对单层单道及单层多道熔覆层熔覆层成形特征的影响;其次,通过扫描电镜、EDS、XRD分析TIG熔覆层、激光熔覆层和激光-电弧复合热源熔覆层的显微组织结构及物相组成。分析不同组织成分及物相组成对熔覆层性能的影响;最后,通过显微硬度仪及洛氏硬度仪对熔覆层的显微硬度和洛氏硬度进行测试分析;通过均匀腐蚀法测量熔覆层在高温浓硫酸中的腐蚀速率;通过扫描电镜、EDS等检测手段对熔覆层腐蚀后的形貌及元素成分进行检测并对其腐蚀机理进行阐述分析;通过电化学工作站对熔覆层的电化学腐蚀性进行检测。试验结果表明:单层单道熔覆时,三种热源熔覆层都与基体都实现了良好的冶金结合。激光熔覆层宏观形貌最好、稀释率最低。其次为激光-电弧复合热源熔覆层。而TIG熔覆层成形较差、稀释率最高。激光-电弧复合热源可以通过更小的激光功率达到与激光熔覆层相近的宏观形貌。熔覆层内的物相主要有Ni2.9Cr0.7Fe0.36、Fe Ni3、Fe0.64Ni0.35、γ-(Fe,Ni)等,与XDB-6铸造合金差异较大。激光熔覆层的组织较细小、TIG熔覆层组织粗大、激光-电弧复合热源熔覆层组织介于两者之间。TIG熔覆层的显微硬度约为HV0.2500~HV0.2700,激光熔覆层的显微硬度约为HV0.2600~HV0.21000,激光-电弧复合热源熔覆层的显微硬度约为HV0.2500~HV0.2900,XDB-6铸造合金的显微硬度为HV0.2550。TIG熔覆层的洛氏硬度约为HRC52,激光熔覆层约为HRC63,激光-电弧复合热源熔覆层约为HRC60,XDB-6合金约为HRC53。在120℃,98%浓硫酸中,TIG熔覆层的腐蚀速率为0.0298 mm/a激光熔覆层的腐蚀速率为0.0205 mm/a、激光-电弧复合热源熔覆层的腐蚀速率为0.0224 mm/a,XDB-6铸造合金的腐蚀速率为0.02mm/a。熔覆层及XDB-6合金的腐蚀等级均为4级。激光熔覆层与激光-电弧复合热源熔覆层的耐腐蚀性与XDB-6相近,同时两者的硬度远高于XDB-6。以上研究表明,熔覆层的显微结构及物相组成均与XDB-6铸造合金有较大差异,但熔覆层的洛氏硬度和耐腐蚀性均符合企业技术要求。所以使用熔覆的方法在廉价基体材料上制备耐高温浓硫酸熔覆层可以代替全铸造耐腐蚀合金阀门,从而达到降低成本的目的。
[Abstract]:The sulphuric acid production and chemical industry have a great deal of demand for high temperature resistant concentrated sulfuric acid valves. The traditional high temperature concentrated sulfuric acid valves are mostly made of corrosion resistant alloys. Because of the strong corrosiveness of high temperature concentrated sulfuric acid, the price of metal materials which meet the requirements of performance is high and the manufacturing cost of the sulphuric acid valve is high. To meet the technical requirements and low price valve products, according to the requirements of relevant enterprises, our team proposed to use TIG heat source, laser heat source and laser arc composite heat source to cover a layer of corrosion resistant alloy on relatively low price metal matrix, and reduce the cost of corrosion resistant valve while maintaining its original property. The technical requirements for the sulfuric acid corrosion resistant equipment are: hardness HRC40, corrosion rate 0.1a/mm and corrosion resistance grade to 5. First, a test platform of heat source system was established. According to the composition of the XDB-6 corrosion resistant cast alloy in Zhejiang special alloy process equipment Co., Ltd., the corrosion resistant alloy powder suitable for cladding was developed. 304 Stainless steel is the matrix material, using TIG heat source, laser heat source and laser arc composite heat source to melt corrosion resistant alloy on the surface of the matrix. The influence of different process parameters on the forming characteristics of single layer and single layer multichannel cladding layer is analyzed. Secondly, the TIG cladding layer, laser cladding layer and laser coating are analyzed by scanning electron microscope, EDS and XRD. The microstructure and phase composition of the cladding layer of the arc compound heat source. The effects of different composition and phase composition on the properties of the cladding layer were analyzed. Finally, the microhardness and Rockwell hardness of the cladding layer were measured and analyzed by the microhardness tester and the Rockwell hardness tester, and the cladding layer was measured in the high temperature concentrated sulfuric acid by homogeneous corrosion method. The corrosion rate was detected by scanning electron microscope (SEM) and EDS. The corrosion mechanism of the cladding layer was examined and the corrosion mechanism was analyzed. The electrochemical corrosion of the cladding layer was detected by electrochemical workstation. The results showed that the three kinds of heat source cladding layers were all solid with the matrix when single channel cladding. The laser cladding layer has the best macroscopic morphology and the lowest dilution rate. The second is the laser arc composite heat source cladding layer, and the TIG cladding layer is poor in forming and the dilution rate is the highest. The laser arc composite heat source can reach the macroscopic morphology near the laser cladding layer through the smaller laser power. The main phase in the cladding layer is the main phase. Ni2.9Cr0.7Fe0.36, Fe Ni3, Fe0.64Ni0.35, gamma (Fe, Ni) are different from that of XDB-6 casting alloy. The microstructure of the laser cladding layer is smaller, the microstructure of the cladding layer of TIG is coarse, and the microstructure of the cladding layer of the laser arc composite heat source is about HV0.2500~HV0.2700, and the microhardness of the laser cladding layer is about HV0.260. 0~HV0.21000, the microhardness of the laser arc composite heat source cladding layer is about HV0.2500~HV0.2900. The microhardness of the XDB-6 casting alloy is about HRC52, the laser cladding layer is about HRC63, the laser arc composite heat source cladding is about HRC60, and XDB-6 alloy is about HRC53. at 120, 98% concentrated sulfuric acid, and TIG cladding. The corrosion rate of the layer is 0.0298 mm/a laser cladding layer and the corrosion rate is 0.0205 mm/a, the corrosion rate of laser arc composite heat source cladding layer is 0.0224 mm/a, the corrosion rate of XDB-6 cast alloy is 4 grade for 0.02mm/a. cladding layer and XDB-6 alloy. The corrosion resistance of laser cladding layer and laser arc composite heat source cladding layer It is similar to XDB-6, and the hardness of the two is much higher than that of more than XDB-6.. The results show that the microstructure and phase composition of the cladding layer are all different from that of the XDB-6 cast alloy, but the Rockwell hardness and corrosion resistance of the cladding layer are all in accordance with the technical requirements of the enterprise. So the high temperature and concentrated sulfuric acid melt is prepared on the cheap matrix material by the method of cladding. The coating can replace the fully cast corrosion-resistant alloy valve, so as to achieve the goal of reducing cost.
【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG174.44

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