The degradation of pump components by corrosion and complex, simultaneous damage mechanisms, e.g., erosion–corrosion and cavitation–corrosion leads to high costs through replacement and maintenance of parts. To increase the lifetime of cost-efficient components with superior casting properties, surface welding of duplex stainless steel on gray cast iron parts was performed using inert shielding gas metal arc surface welding (GMA-SW) and plasma transferred arc surface welding (PTA-SW). The thermal conductivity of the used shielding gas and the preheating temperature influenced the dilution of the surface layers, which had a major impact on the corrosion resistance and the microstructure. Lower cooling rates enhanced diffusion and lead to precipitation of carbides. High heat input and prolonged cooling times during surface welding resulted in high dilution and a carbide network. The corrosion resistance in artificial seawater of those surface layers was substantially reduced compared to surface layers with lower heat input and higher cooling rates. The corrosion of the surface layers in the potentiodynamic polarization test was driven by selective corrosion of the phase boundary between Cr–carbides and Cr–depleted austenite. Passive behavior was observed for surface layers with low dilution, which had homogeneous chromium distribution and no carbide networks. In conclusion, the corrosion behavior of gray cast iron was improved by surface welding with duplex stainless steel. The corrosion resistance of the surface layers produced with PTA-SW with no preheating exceeded that of the surface layers produced with GMA-SW and came close to those of a commercially available duplex stainless steel used as reference material.

中文翻译：

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灰口铸铁上焊接双相不锈钢表面层的耐腐蚀性和显微组织

泵部件因腐蚀和复杂的同时损坏机制（例如侵蚀-腐蚀和气蚀-腐蚀）而退化，导致部件更换和维护成本高昂。为了延长具有卓越铸造性能的经济高效部件的使用寿命，使用惰性气体保护金属弧面焊 (GMA-SW) 和等离子转移弧面焊 (PTA-SW) 在灰铸铁零件上进行双相不锈钢表面焊接）。所用保护气体的导热系数和预热温度影响了表面层的稀释，这对耐腐蚀性和微观结构有重大影响。较低的冷却速率会增强扩散并导致碳化物沉淀。表面焊接期间的高热输入和延长的冷却时间导致高度稀释和碳化物网络。与具有较低热输入和较高冷却速率的表层相比，这些表层在人工海水中的抗腐蚀性能显着降低。动电位极化试验中表面层的腐蚀是由铬碳化物和贫铬奥氏体之间相界的选择性腐蚀驱动的。对于具有均匀铬分布且无碳化物网络的低稀释表面层，观察到钝化行​​为。总之，采用双相不锈钢进行表面焊接改善了灰口铸铁的腐蚀行为。