Phase constitution,microstructure and mechanical properties of a Ni-based superalloy specially designed for additive manufacturing

In this study, a kind of Ni-based superalloy specially designed for additive manufacturing (AM) was investigated. Thermo-Calc simulation and differential scanning calorimetry (DSC) analysis were used to determine phases and their transformation temperature. Experimental specimens were prepared by laser metal deposition (LMD) and traditional casting method. Microstructure, phase constitution and mechanical properties of the alloy were characterized by scanning electron microscopy (SEM), transmission scanning electron microscopy (TEM), X-ray diffraction (XRD) and tensile tests. The results show that this alloy contains two basic phases, γ/γ', in addition to these phases, at least two secondary phases may be present, such as MC carbides and Laves phases. Furthermore, the as-deposited alloy has finer dendrite, its mean primary dendrite arm space (PDAS) is about 30-45 μm, and the average size of γ' particles is 100-150 nm. However, the dendrite size of the as-cast alloy is much larger and its PDAS is 300-500 μm with secondary and even third dendrite arms. Correspondingly, the alloy displays different tensile behavior with different processing methods, and the as-deposited specimen shows better ultimate tensile stress (1,085.7±51.7 MPa), yield stress (697±19.5 MPa) and elongation (25.8%±2.2%) than that of the as-cast specimen. The differences in mechanical properties of the alloy are due to the different morphology and size of dendrites, γ', and Laves phase, and the segregation of elements, etc. Such important information would be helpful for alloy application as well as new alloy development.     

单晶凝固组织的样品尺寸效应

通过对不同直径的单晶样品的凝固实验，研究了样品尺寸对单晶凝固组织的影响规律，研究发现，随样品尺寸减小，单晶凝固组织被细化，尤其一次枝晶间距λ1和枝晶间γ′相尺寸对样品尺寸的依赖性更为明显；样品尺寸影响的要质在于此表面积的变化，进而对凝固过程温度梯度产生影响，最终作用于凝固组织和力学性能，一次枝晶间距λ1和枝晶间γ′尺寸与样品的比表面积近拟呈线性关系，样品尺寸变化，明显改变了单晶生长过程的温度梯度和合金的高温持久寿命。     

GJB712A-2001航天用GH4169高温合金锻制圆饼规范介绍

介绍了GH 4 16 9高温合金锻制圆饼规范的修订内容 ,对其主要技术指标作了简要说明 ,并与国外同类标准进行了比较。     

Microstructure and Its Influence on Mechanical Behaviour of Directionally Solidified DZ38G Superalloy

The features of microstructure and theirinfluence on mechanical properties onstress-rupture as well as thermal fatigue ofdirectionally solidified DZ38G nickel-base su-peralloy have been investigated.It has beenfound that the contents of carbides on grainboundaries are increased and morphology of γ'-precipitates has been changed after testing.Particularly γ'-precipitates coalesced intoraft-like in morphology perpendicular to theapplied stress-axis have been observed thathas no detrimental effect on the stress-rupturebehaviour.The tendency of σ-formation hasalso been discussed.The σ-phase can be avoidedwhen the process parameters are chosenappropriately during solidification.     

Ca,Mg对镍基高温合金力学性能和热塑性的影响

本文研究了单加或同时添加微量Ca和Mg对变形及铸态镍基高温合金力学性能和热塑性的影响。试验表明,适量的Mg或Ca、Mg对提高合金的持久断裂寿命、高温拉伸塑性以及改善热塑性都取得良好效果。     

Thermal—Mechanical Fatigue Behavior and Life Analysis of Cast Ni—base Superalloy K417

In-phase(IP) and out-of-phase(OP)thermal-mechanical fatigue(TMF) behavior of cast Ni-base superalloy K417 was studied.All experiments were carried out under total strain control with temperature cycling between 400-850℃.Both in-phase and out-of-phase TMF specimens exhibited cyclic hardening followed by cyclic softening at the minimum temperature.Besides,they cyclically hardened in the early stage of life followed by cyclic softening at the minimum temperature.Besides,they cyclically hardened in the early stage of life followed by cyclic softening at the maximum temperature.OP TMF life was longer than of IP TMF.Various damage mechanisms operating in different controlled strain ranges and phasing were discussed.A few life prediction methods for isothermal fatigue were used to handle TMF fatigue and their applicability to superalloy K417 was evaluated.The SEM analysis of the fracture surface showed that transgranular fracture was the principal cracking mode for both IP and OP TMF.Oxidation was the main damage mechanism in causing shorter fatigue life for IP TMF compared with OP TMF.     

镍基耐海水腐蚀材料的研究概况

综述了镍基耐海水腐蚀材料的研究概况,阐述了Ni-Cu,Ni-Cr,Ni-Mo和Ni-Cr-Mo合金的耐腐蚀性能及其影响因素,展望了该材料研究未来的发展方向。     

铸造镍基K3合金的激光熔覆开裂及工艺研究

研究了铸造镍基Ｋ３合金的激光熔覆过程，分析了原始组织及激光熔覆工艺参数对熔覆裂纹形成的及作用；探讨了使用激光熔覆技术对损伤的Ｋ３合金叶片进行修复的可能性。研究结果表明，Ｋ３合金中沿界分布的低熔点共晶及碳化物是引起激光熔覆开裂的主要因素，采用较高的功率密度和较快的扫描速度进行激光熔覆，可减少热影响区范围，明显地抑制熔覆裂纹的产生。     

DZ125合金HY3涂层防护性能研究

研究了ＤＺ１２５合金ＮｉＣｒＡｌＹＳｉ防护涂层抗氧化抗腐蚀性能。试验表明，在１１００℃循环氧化加速试验条件下及１０５０℃循环氧化长寿试验中，涂层对合金起到了很好的防护作用，在９００℃燃气热腐蚀条件下，ＮｉＣｒＡｌＹＳｉ     

高温合金材料在铝电解工业中的应用探讨

对高温合金在铝电解工业用作惰性金属阳极材料的选择进行阐述，并就实际应用过程中的抗氧化耐腐蚀性进行探讨；阐述适用于铝电解工业的惰性阳极合金所应具备的必要条件和必须解决的问题，并介绍目前有关的研究动态和研究方向。