纯Ni母材及焊缝在熔融Na2SO4-K2SO4中热腐蚀研究  

Hot Corrosion of Pure Nickel and Its Weld Joints in Molten Na_2SO_4-K_2SO_4 Salts

作　　者：王希靖[1] 王博士[1] 杨超[1] 杨艳[2] 沈斌 WANG Xijing; WANG Boshi; YANG Chao; YANG Yan; SHEN Bin(State Key Laboratory of Gansu Advanced Nonferrous Metal Materials, Lanzhou University of Technology, Lanzhou 730050, China State Key Laboratory of Nickel and Cobalt Resources Comprehensive Utilization, Jinchuan Group Cooperation Ltd., Jinchang 737104, China)

机构地区：[1]兰州理工大学有色金属先进加工与再利用省部共建国家重点试验室,兰州730050 [2]金川集团股份有限公司镍钻资源综合利用国家重点实验室,金昌737104 [3]金川镍都实业有限公司,金昌737104

出　　处：《中国腐蚀与防护学报》2018年第5期495-501,共7页Journal of Chinese Society For Corrosion and Protection

基　　金：镍钴资源综合利用国家重点实验室项目(301170501)

摘　　要：通过对纯Ni在PAW和PAW+TIG两种不同焊接工艺下得到的焊缝及母材进行恒温的熔融硫酸盐热腐蚀实验,对腐蚀产物横断面进行形貌观察及微区成分分析,研究不同焊缝工艺下得到的焊缝组织和母材在恒温热腐蚀期间的腐蚀产物分布特征、腐蚀行为和腐蚀机理。结果表明,采用PAW和PAW+TIG两种焊接工艺方法所得焊缝的晶粒尺寸相差不大,在熔融Na_2SO_4-K_2SO_4中焊缝的抗热腐蚀性能相近,但明显低于母材的抗热腐蚀性能。在热腐蚀期间,热腐蚀形态往往包括一个位于表面氧化膜内侧、向基体内部延伸的内氧化物与内硫化物分布区的硫化-氧化循环过程,S在热腐蚀过程中起着重要的作用。针对纯Ni的PAW+TIG焊接方法比较符合工业实际生产及应用要求。Hot corrosion behavior of pure nickel and its joints, which were prepared by plasma arc welding（PAW） and plasma arc welding ＋ tungsten inert gas（PAW ＋ TIG） respectively, in molten Na_2SO_4-K_2SO_4 salts at 900 ℃ are investigated by means of weight loss measurements, X-ray diffractometer（XRD）, scanning electron microscopy（SEM）, and energy dispersive X-ray spectroscopy（EDS）. Experimental results show that the grain size and hot corrosion resistance of the welds obtained by the two welding methods have little difference, while the corrosion resistance of the joints is inferior to that of the base metal. The hot corrosion kinetics of the specimens follow linear power laws, and the corrosion products on the base metal and joints are mainly composed of NiO and Ni3S2. Cross-sectional morphologies and corresponding elemental maps indicate that corrosion product composed of an outer dense scale,beneath which there existed an internal zone of oxides and sulfides. According to these results, a mechanism of synergistic oxidation and sulfidation for hot corrosion of pure nickel is confirmed. That is, the distribution of internal oxides and sulfides, located beneath the outer oxide scale, extends to the substrate. In other words, the sulfidation-oxidation cycle process and sulfur play an important role in the process of hot corrosion. So,for pure nickel welding, PAW＋TIG welding method meets the requirements of the actual industrial production and application.

关 键 词：纯NI PAW+TIG焊接 熔盐 热腐蚀机理 硫化-氧化循环 

分 类 号：TG174.4[金属学及工艺—金属表面处理]