GH4169高温合金的静态再结晶动力学

对GH4169高温合金在Gleeble-3500热模拟实验机进行了双道次和单道次热压缩实验。分析了变形温度、应变速率、间隔保温时间、变形量和初始晶粒尺寸对GH4169高温合金静态再结晶体积分数的影响。实验结果表明:变形温度越高、应变速率越大、道次间隔时间越长,变形量越大,初始晶粒度越小,静态再结晶体积分数越大。根据实验结果,建立了GH4169高温合金的静态再结晶模型,并将所建立的模型的预测结果和实验结果进行了对比分析,二者比较吻合。     

Suppression of notch wear of a whisker reinforced ceramic tool in air-jet-assisted high-speed machining of Inconel 718

This paper describes the notch and flank wear specific to a SiC whisker reinforced alumina tool in air jet assisted (AJA) turning of nickel-base superalloy Inconel 718 at high cutting speeds. An AJA machining experiment has revealed that the air jet applied to the tool tip in addition to coolant dramatically reduces the depth-of-cut notch wear. As a result, the width of flank wear, but not the size of notch wear, determined the life of a ceramic tool in AJA machining of Inconel 718. This is a reason for the large extension and small variation of the tool life when high speed AJA machining is adopted. The maximum tool life length reached 2160 m at a cutting speed of 660 m/min under the given cutting conditions. Finally, the mechanisms of the notch and flank wear of a SiC whisker reinforced alumina tool in AJA machining are discussed from the viewpoints of tribochemical reactions and tool wear anisotropy.     

GH4169合金的高温应力松弛行为及蠕变本构方程

针对涡轮盘用GH4169合金,在不同温度(550,650,750℃)下开展了应力松弛试验,并根据应力松弛曲线建立了蠕变本构方程。结果表明:GH4169合金在不同温度下的应力松弛曲线呈现出相同的特点,整个应力松弛过程可以分为快速松弛和缓慢松弛并趋于稳定两个区段;拟合曲线与试验曲线的符合程度表明二阶指数衰减函数可以很好地用来描述该合金的应力松弛过程;不同温度下应力-蠕变应变速率关系曲线可划分为低应力区、过渡区和高应力区三个区段,在低应力区与高应力区,应力与蠕变应变速率关系基本呈线性相关;通过Origin8.0软件对应力-蠕变应变速率关系曲线进行拟合得到了不同温度下的材料常数,建立了该合金的蠕变本构方程。     

DD32单晶高温合金过渡液相扩散连接

为了提高DD32单晶高温合金过渡液相(TLP)扩散焊接头的力学性能,采用扫描电镜(SEM)和能谱分析仪(EDS)研究接头微观组织,TLP扩散焊过程中基体组织的变化,以及持久过程中基体组织的变化。结果表明,接头由连接区和基体区所组成,未发现明显的扩散区特征。连接区由等温凝固区和残余液相区组成。TLP扩散焊过程对基体组织有重要影响,接头需进行焊后热处理。此外,在持久过程中基体内产生了N型筏。控制TLP扩散焊接头内晶界的形成,可以有效提高接头力学性能。     

Intermetallic phase formation during brazing of a nickel alloy using a Ni–Cr–Si–Fe–B quinary filler alloy

ABSTRACT

Fundamental understanding of the intermetallic phase formation is the key for enhancing the robustness and reliability of the brazed joints. The paper addresses the phase transformations during brazing of the Hastelloy X nickel-base superalloy using the quinary Ni–13Cr–4.5Si–4.2Fe–2.8B (wt-%) braze alloy. The mechanisms of intermetallic formation via solidification and solid-state precipitation are discussed. The athermal solidification zone (ASZ) is featured by the formation of brittle and hard borides and boro-silicides that are formed via eutectic reactions. However, in contrast to other commercial B-bearing Ni-based filler alloys, it was identified that the presence of a high-volume fraction of eutectic gamma solid solution between boride phases within the joint centreline can alleviate the deleterious effect of the intermetallic phases on the joint toughness.     

Evolution of microstructure and properties of internal nitride dispersion strengthened alloy before nitriding

Internal nitride dispersion strengthened superalloy is a new type of high performance superalloy for combustion chamber. The background and development of this alloy were firstly introduced. And then the microstructure and properties of NS163 which is a typical internal nitride dispersion strengthened alloy were investigated. The results show that the microstructure of NS163 is simple in the temperature range of 900??1250??, which is composed of austenite matrix and MC carbide. The recrystallization behavior of the cold- rolled sheet under the test condition was studied systematically. It is found that the solid solution temperature of the finished product should be 1200??, and after solid solution at 1200??, the sheet has 5 grade average grain size, excellent cold workability and low tensile strength at high temperature. The above results can help to optimize the microstructure of NS163 alloy sheet before nitriding and provide a basis for the evaluation of the strengthening effect of the alloy after internal nitriding.     

纯净化DZ125合金返回料研究

在工业化生产型真空感应炉中,对定向高温合金DZ125返回料净化技术进行研究,用电子束纽扣法测定夹杂数量,并对净化后的100%返回料锭和常规工艺生产的100%新料锭在纯净度、化学成分、力学性能和铸造性能方面进行对比.结果表明:净化技术显著降低返回料中的氧化夹杂含量,净化后的100%返回料锭和100%新料锭相比,氧化夹杂数量稍有降低,持久性能略有提高,化学成分、室温拉伸性能和铸造性能均相当.     

Ni基高温合金的真空冶炼脱硫

研究了Ni基高温合金用CaO坩埚真空感应精炼过程中含S量的变化；发现只用CaO坩埚并不进行脱S．通过熔体化学成分变化研究了加Al的脱S作用；结合坩埚壁的XRD分析和成分分析数据讨论了CaO坩埚脱S机理；对CaO坩埚内壁表面发生的化学反应进行了热力学计算和讨论．     

Creep-fatigue crack growth behavior in GH4169 superalloy

This study aims to examine the crack growth behavior of turbine disc GH4169 superalloy under creep-fatigue loading. Crack growth experiments were performed on compact tension specimens using trapezoidal waveform with dwell time at the maximum load at 650 °C. The crack growth rate of GH4169 superalloy significantly increased with dwell time. The grain boundaries oxidize during the dwell process, thereby inducing an intergranular creep-fatigue fracture mode. In addition, testing data under the same dwell time showed scattering at the crack growth rate. Consequently, a modified model based on the Saxena equation was proposed by introducing a distribution factor for the crack growth rate. Microstructural observation confirmed that the small grain size and high volume fraction of the d phase led to a fast creep-fatigue crack growth rate at 650 °C, thus indicating that two factors, namely, fine grain and presence of the d phase at the grain boundary, increased the amount of weakened interface at high temperature, in which intergranular cracks may form and propagate.     

蠕变空洞尺寸对镍基高温合金应力场的影响规律

为研究在热等静压作用下蠕变空洞大小对镍基高温合金的应力场分布的影响,采用有限元方法分别计算了不同尺寸的蠕变空洞附近的应力场分布情况。结果表明,空洞顶点距离γ′相中心越近,镍基高温合金中最大von Mises应力和最高弹性应变能密度越小;当蠕变空洞的顶点到γ′相中心距离相同时,在垂直方向上,基体垂直通道上von Mises应力和弹性应变能密度从上到下递增,基体水平通道上递减。而且随着蠕变空洞半径增大,合金中基体通道上的von Mises应力和弹性应变能密度递增和递减的趋势越明显。