GH718合金氢渗透特性的研究

ＧＨ７１８合金氢渗透特性的研究徐坚，孙秀魁，刘清泉，陈文绣（中国科学院金属研究所，快速凝固非平衡合金国家重点实验室沈阳１１００１５）１前言ＧＨ７１８（ＩＮＣＯＮＥＬ７１８）合金广泛用作为涡轮叶片、氢燃发动机、核反应堆器壁等部件的材料．由于使用环境中氢...     

激光退火对Inconel 718微观组织和硬度的影响

研究激光退火对Inconel718时效合金的显微组织和硬度的影响.一台2.5kW的CO2激光机被用来照射试样的表面.在激光能作用下,试样表面层被加热后空冷.通过控制激光工艺参数,在表面不发生熔化的前提下,能够使一定厚度表面层内的硬度降低到标准退火合金的水平,而不影响试样内部母材的硬度.显微组织观察显示表面层的基体强化相(γ″和γ‘)在激光照射过程中被固溶,而其它二次相没有变化.γ″和γ‘的固溶被确定是表面层硬度下降的原因.在其它试验条件不变时,确立了退火层生成时由激光散焦距离和扫描速度描述的工艺参数范围.     

激光熔覆镍基粉末涂层的研究

分析了激光熔覆表面处理技术对镍基自熔性合金粉末材料性能的要求，研究了合金粉末的化学成分、微观组织及熔覆层的性能，并对涂层的耐磨性进行了分析。     

Study on the preparation and microstructure of a single-crystal hollow turbine blade

This paper studied the structural design of a ceramic core and a blade, ceramic core localization, shell preparation, casting process, core leaching technology, and the heat treatment process of a single-crystal hollow turbine blade. The results show that the single-crystal structure solidification sequence of the blade platform is consistent with the cooling sequence and the pulling-out direction of the blade. The primary dendrites were obviously enlarged with the increase of the blade thickness owing to the change in the local cooling rate. Besides, the γ′ phase had a high uniform size distribution ranging from 0.40 to 0.60?µm after heat treatment, and the cubic degree was more homogeneous in comparison with the as-cast microstructure, which are favorable for the superalloy structure. Moreover, γ′ phase size gradually increased and its quantity gradually reduced owing to the increase of the wall thickness in the growth direction.     

Crystallographic analysis on small fatigue crack propagation behaviour of a nickel-based single crystal superalloy

In situ observations by scanning electron microscopy show that small fatigue cracks in a nickel-based single crystal superalloy are inclined to the loading direction and propagate in dominant crystallographic manners. In order to evaluate the driving forces for inclined crack propagation, three-dimensional anisotropic linear elastic finite-element analysis is conducted. The plastic zone size on the dominant slip plane has been calculated and proposed to correlate the fatigue crack growth. It is shown that this parameter takes into account both material anisotropy and octahedral fracture modes, and it can effectively characterize small crack propagation behaviour.     

吹砂、抛光及其电解腐蚀后处理对单晶高温合金表面组织和再结晶行为的影响

采用吹砂处理、砂带抛光、毡轮抛光3种表面处理使铸态单晶(SX)Ni基高温合金叶片表面形成塑性变形层,对叶片表面变形层进行电解腐蚀实验,然后进行标准热处理,研究了单晶高温合金叶片表面处理的变形层及其电解腐蚀后显微组织。结果表明:3种表面处理的铸态单晶高温合金叶片表面变形层深度分别约为6,3.5μm和2μm,并在吹砂处理和砂带抛光的表面变形层周围存在显微裂纹;表面变形层电解腐蚀过渡区内存在大量γ′变形组织,且3种表面处理的塑性变形残存量依次递减,而变形层完全电解腐蚀区内无塑性变形痕迹;标准热处理后,变形层未电解腐蚀区存在凹陷特征和再结晶晶粒,但无塑性变形痕迹;变形层完全电解腐蚀区无明显凹坑和再结晶晶粒。     

冷拉减面率对C形环用Inconel X-750丝材组织性能的影响

文章通过冷拉拔加工制备减面率为0%、30%、60%的Inconel X-750丝材,分别在650℃、730℃、810℃下时效处理16h,研究冷拉减面率对X-750合金组织性能的影响,特别是减面率对γ′相形状、分布、数量及尺寸的影响。经定量分析,增大冷拉减面率除了有细化晶粒的作用外,还能一定程度地增加γ′相析出的颗粒数量及体积分数,减小γ′相尺寸,进一步加强沉淀强化的作用。时效温度对X-750丝材的晶粒尺寸没有明显影响,对γ′相的数量、尺寸及形状影响较大。采用730℃时效处理16h的标准工艺制备的X-750丝材,经加工为弹簧后制造成金属C形密封环,其回弹量及泄漏率均满足要求,实验条件下密封性能良好。     

Characteristic study of N07718 superalloy surface prepared by cold spray

For better performance in erosive–corrosive, wear and other extreme environmental conditions surface properties of metals and alloys are usually altered by different techniques. Amongst the various surface coating techniques cold spraying is a relatively new and less reported method. Coating formation at energy lower than the melting stage of materials brings novelty to this process. In this study surface of UNS No. - N07718 alloy is altered by cold spraying chromium-carbide (nickel-chromium) layer. The microstructure properties of this cold sprayed surface are observed by various characterization techniques and the results are used to study mechanism of coating layer formation by cold spray process. This newly developed cold sprayed surface is found to be eligible for further testing in wear and erosive-corrosive environmental conditions.     

Oxidation behaviors of Ni-Cr-Al superalloy foams at 1 000 ℃ in air

The oxidation behaviors of Ni-16Cr-xAl （x=4.5%, 9.0%, mass fraction） superalloy foams in air at 1000℃ were investigated. The effects of AI content on the resistance to high temperature oxidation were examined. The oxidation mechanisms of the foams were discussed. The results show that the resistance to the oxidation of the Ni-16Cr-xA1 based alloy at 1 000 ℃ increases with the content of A1 increasing from 4.5% to 9.0%. Complex oxide products are formed on the surface of the superalloy foams after the oxidation. Cr203 and A1203 are the predominant oxides for the scales of the foams with 4.5% A1 and 9% A1, respectively. Excellent high temperature oxidation resistance and superior pore conformation stability for the Ni-16Cr-xA1 based superalloy foam with 9% A1 can be mainly attributed to the formation of relatively continuous and protective A1203 oxides on the surface of the foam.     

A modern and robust methodology for modeling anisotropic creep characteristics of Ni-based DS and SC superalloys

According to more recent work,the Wilshire equations have shown good prediction accuracy in a wide range of materials and stress-temperature conditions,particularly in extrapolation of short term results to long term predictions.In the current paper,this methodology was further developed for modeling anisotropic creep characteristics(i.e.minimum creep strain εmin ,stress rupture life tf and time to a specified strain tε)of four typical Ni-based directionally solidified(DS)and single crystal(SC)superalloys,where a simple orientation factor related to the ultimate tensile strength(UTS)was introduced.The application of these simplistic approaches showed that the anisotropic creep characteristics in a wide range of stress-temperature conditions can be accurately simulated.Meanwhile,during the application of the modified Wilshire equations,break points occurring at the specified stress levels agree well with the transition of creep deformation mechanisms occurring in different stress regions,which provides confidence for using this method.