Si对625合金激光熔覆层高温氧化特性的影响

利用循环氧化法，研究了不同Si含量（0%，1%，3%，质量分数）的625合金熔覆层在700、800、900 ℃下氧化144 h后的高温氧化行为。用XRD分析了氧化物相。通过SEM/EDS研究了氧化物表面和截面的形貌、元素组成和氧化膜的厚度。结果表明，不同温度下试样的氧化动力学都保持抛物线规律，随着温度的升高，氧化增重逐渐增加。通过观察，在900 ℃时，0% Si含量的625合金熔覆层出现了氧化膜大面积剥落的情况，3% Si含量的合金熔覆层氧化膜保持完整。在700 ℃时，随着Si含量增加，氧化膜表面的氧化颗粒尺寸减小且更加致密，同时促进了Cr₂O₃氧化物的生成。在700 ℃下，0 % Si含量的试样出现了大片的内氧化区域；1% Si含量的试样基体部分出现了2处条状的含Ni，Cr，Mo的氧化物相区；而3% Si含量的试样氧化后由于生成了富Si的内氧化层，这阻止了内氧化的发生。外层Cr₂O₃氧化膜和内层SiO₂的联合作用既阻止了O阴离子的渗入也抑制了Fe等金属离子的扩散，提高了合金熔覆层的抗氧化性。

Effect of Si on High Temperature Oxidation Characteristics of Laser Cladding 625 Alloy

The high temperature oxidation behavior of 625 alloy cladding layer with different Si contents was studied by cyclic oxidation method after 144 h oxidation at 700, 800 and 900 °C. The oxide phase was analyzed by XRD. The surface and cross section morphology, elemental composition and oxide film thickness were studied by SEM/EDS. The results show that the oxidation kinetics of the samples at different temperatures keep a parabolic law, and the oxidation mass gain increases gradually with the increase of temperature. The oxidation film of 0wt% Si 625 alloy cladding sample peels off in a large area at 900 °C, while the oxidation film of 3wt% Si alloy cladding sample remains intact. With the increase of Si content at 700 °C, the oxidation particles on the surface of the oxide film decrease in size and become denser, which promotes the formation of Cr₂O₃. At 700 °C, a large area of internal oxidation appears in 0wt% Si sample, there are two strip oxides containing Ni, Cr and Mo in the substrate of 1wt% Si sample, while the inner oxidation of 3wt% Si samples is prevented due to the formation of Si-rich inner oxidation layer. The combined effect of the outer layer of Cr₂O₃ oxide film and the inner layer of SiO₂ not only prevents the infiltration of O anions but also inhibits the diffusion of Fe and other metal ions, thus improving the oxidation resistance of the alloy cladding.