Microstructure and Impact Toughness of F12 Steel Welded Joint after Service at High Temperature for a Long Term
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摘要: 利用光学显微镜、扫描电子显微镜、能谱仪、X射线衍射仪和冲击试验机等研究了F12钢焊接接头高温运行16.5万h后的显微组织和冲击韧性。结果表明：高温运行16.5万h后，F12钢焊接接头中的马氏体发生分解，接头中的析出相主要为M23C6型碳化物，其在晶界析出并聚集长大，呈孤立的颗粒状或链状分布;F12钢焊接接头出现显著的时效脆化现象，这与组织中M23C6相的析出、聚集长大有关;母材冲击断口为沿晶断裂，焊缝金属的为解理断裂。Abstract: Microstructure and impact toughness of F12 steel welded joint after service at high temperature for 165 000 h was studied by optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, X-ray scattering technique and impact testing. Results show that after service at high temperature for 165 000 h, martensite in the welded joint of F12 steel decomposed, and precipitation phases in the welded joint mainly were M23C6 carbide, and they precipitated at the grain boundaries, and then gathered and grew with isolated granule or chain-like distribution. The welded joint exhibited obvious aging brittleness, this attribured to gathering and growing of M23C6 phase. The base metal in the joint was intergranular fracture morphology, and the weld metal was cleavage fracture morphology.
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