High temperature oxidation behavior of aluminide on a Ni-based single crystal superalloy in different surface orientations

An investigation on oxidation behavior of coated Ni-based single crystal superalloy in different surface orientations has been carried out at1100 ℃. It has been found that the {100} surface shows a better oxidation resistance than the {110} one, which is attributed that the {110}surface had a slightly higher oxidation rate when compared to the {100} surface. The experimental results also indicated that the anisotropic oxidation behavior took place even with a very small difference in the oxidation rates that was found between the two surfaces. The differences of the topologically close packed phase amount and its penetration depth between the two surfaces, including the ratio of α-Al2O3 after 500 h oxidation, were responsible for the oxidation anisotropy.     

应力时效对镍基单晶合金DD11组织及持久性能的影响

研究了1070℃/100MPa应力时效对镍基单晶合金DD11组织和持久性能的影响,通过扫描电镜和透射电镜对应力时效前后的组织进行了观察和分析,并对合金应力时效前后的持久性能进行了测试与分析。实验结果表明:应力时效前50h是形筏阶段,竖直方向的γ相通道逐步变窄或消失,水平方向的γ相通道宽度逐步增加,立方状γ′相在应力的作用下向水平方向扩展并相互连接在一起逐渐形成筏排形貌。应力时效50h后是筏排粗化阶段,随应力时效时间的延长,组织缓慢粗化,但是筏排形貌基本保持稳定。对应力时效后的组织进行1 070℃/140 MPa持久性能测试,结果表明,在形筏阶段持久寿命基本保持稳定,在筏排粗化阶段,持久寿命逐步下降。应力时效500h后,持久寿命由热处理后初始状态的360h左右降低至140h左右。研究结果表明,γ相通道尺寸的粗化和组织的筏排化是持久性能衰退的主要因素。     

镍基高温合金高速铣削加工表面完整性

采用高速铣削加工试验,研究切削速度对2种不同的镍基高温合金FGH95和Inconel718已加工表面完整性的影响规律,并观察高速铣削加工后的切屑形貌。试验结果表明:在较低切削速度范围内(800~2 000 m/min),切削速度对表面粗糙度的影响很小,两者表面粗糙度相差不大,但在较高的切削速度范围内(>2 000 m/min),FGH95的表面粗糙度要大于Inconel718的表面粗糙度。在相同切削条件下,Inconel718的加工硬化率和加工硬化层深度要明显比FGH95的大,并且Inconel718表面白层的厚度大于FGH95表面白层厚度。高速铣削加工FGH95和Inconel718切屑均出现明显的锯齿化现象,并且随着切削速度的提高,锯齿化程度不断加剧以至变为碎屑。     

镍基合金CMSX-4在3.5wt.% NaCl溶液中的腐蚀行为

研究二代镍基合金CMSX-4在质量分数为3.5% NaCl溶液中的腐蚀行为,对该类合金在海洋性环境条件下的应用具有深远意义。通过动电位极化方法研究室温条件下镍基合金CMSX-4在3.5 wt.% NaCl溶液中的电化学行为,利用扫描电子显微镜（SEM）、能谱分析仪（EDS）和X射线光电子能谱仪（XPS）对合金表面阳极腐蚀产物进行微观形貌观察及成分分析。研究表明,CMSX-4合金具有一定的钝化能力,钝化区间比较宽广;在镍基合金CMSX-4表面上形成的腐蚀产物可大致分为两层,表层主要由Ni （OH）₂、Cr （OH）₃、Co （OH）₂和Al （OH）₃等氢氧化物组成,内层主要分布着NiO、Al₂O₃、CoO、Cr₂O₃和CrO₃等氧化物及组成合金基体的各种金属;由Ni （OH）₂和Cr （OH）₃等氢氧化物组成的腐蚀产物膜外层能够在腐蚀介质和金属之间产生较好的屏蔽效果;构成腐蚀产物膜内层的NiO、Al₂O₃、Cr₂O₃和CrO₃等氧化物有利于产物膜内层与外层之间建立一定的空间电荷区,对稳定腐蚀产物内层有很大帮助。研究表明CMSX-4合金在海洋性环境中具有一定的耐蚀性能。     

粉末铁基高温合金的制备工艺研究

采用粉末机械合金化-温压成型-真空烧结等方法制备了氧化物弥散强化铁基高温合金MA956,并对其制备工艺和组织性能进行了研究。结果表明,高能振动球磨4h粉末颗粒细小均匀,已经基本实现了合金化,将其在120℃、500MPa条件下进行温压成型,压坯密度比常温模压工艺提高了0．3g／cm3;烧结温度对烧结体组织和性能有较大的影响,粉末压坯在1350℃烧结其致密度最高,为90．8％,且显微组织致密性好。     

Pore defects in a nickel-based superalloy with high Ti content

Pores are uncommon defects in superalloy bars, which deserve to be investigated. In this work, a type of pore defect within GH4710 nickel-based superalloy was investigated by 3D X-ray imaging method combined with metallographic analysis. 3D X-ray imaging was used for locating and visualizing the defects in the alloy. The 3D X-ray imaging result of the defects showed a good agreement with the defect anatomical morphologies. It was observed that the pore defect was accompanied by MC carbides, micro-crack, and non-metallic inclusions. The origin of pore defect was attributed to the shrinkage pores, inclusion and the complex precipitates. The analysis showed that the pore defects in GH4710 alloy was associated with strong micro-segregation and complex phase precipitation during solidification, induced by the high weight content of Ti and C in the alloy.     

弯曲晶界对GH49合金蠕变过程中位错组态的影响

本文用电子金相观察了GH49合金两种不同的晶界状态,试样在蠕变断裂过程中位错组态的变化,并研究了位错与晶内γ′相及晶界碳化物沉淀间的相互作用。研究表明:平直晶界试样,晶内蠕变主要是位错攀移越过γ′相所引起,晶界运动受控于晶界滑动。而弯曲晶界试样,晶内蠕变是位错攀移越过r′相及位错切割γ′相所引起,晶界运动受控于晶界滑动与弯曲段内的“回复”移动。因而,弯曲晶界提高了晶内蠕变速率而降低了晶界滑动速率。这就有效地阻止了裂纹的连接、扩展,大幅度地提高了蠕变第三阶段的断裂抗力,从而延长了蠕变寿命及蠕变断裂塑性。