Si对Ni-Cr-Mo合金熔覆层高温耐腐蚀性能的影响

Effect of Si on High-Temperature Corrosion Resistance of Ni-Cr-Mo Alloy Cladding Layer

摘要:

为研究Si含量对Ni-Cr-Mo系合金熔覆层耐高温腐蚀性能的影响，利用激光熔覆技术制备了4种不同Si含量的熔覆层。采用失重法测试了4种熔覆层在模拟垃圾发电腐蚀环境中多种温度下的耐腐蚀性能。通过对4种熔覆层在600及650 ℃下腐蚀产物的特性分析，发现Si的加入有助于腐蚀产物中富Cr氧化皮的稳定性。还可以通过“钉扎”作用提升富Cr氧化皮与基体的粘结性，从而有效提高熔覆层的耐腐蚀性能。但Si含量并非越多越好。当温度提升到600 ℃以上，含3%（质量分数，下同）Si的合金展现了最佳的耐腐蚀性能。这是由于含3% Si的合金腐蚀层中形成了一层保护性的SiO₂，有助于耐腐蚀性能的提升。而含1% Si的合金由于Si含量较低，含5% Si的合金由于Si的偏析严重，均未能形成有效的SiO₂保护层。

Abstract:

To investigate the effect of Si content on the high-temperature corrosion resistance of Ni-Cr-Mo alloy cladding layers, four cladding layers with different Si contents were prepared by laser melting technique. The corrosion resistance of the four cladding layers was tested by the mass loss method in a simulated waste-to-energy corrosive environment at different temperatures. Through the analysis about the characteristics of corrosion products of four cladding layers generated at 600 and 650 °C, it is found that the Si addition is beneficial to the stability of the Cr-rich oxide in the corrosion products. The adhesion of Cr-rich oxide to the substrate can also be enhanced through the pinning effect, thus effectively improving the corrosion resistance of cladding layer. However, excess Si addition has the negative effect. When the temperature is above 600 °C, the cladding layer with 3wt% Si shows the optimal corrosion resistance. This phenomenon is attributed to the formation of SiO₂ protective layer in the corrosion layer, which improves the corrosion resistance of cladding layer with 3wt% Si. Because of the small Si addition amount and the severe Si segregation, the effective SiO₂ protective layer cannot be formed in the cladding layers with 1wt% and 5wt% Si, respectively.