Influence of Carbon Content and Solidification Condition on Incipient Melting of DS Superalloy MAR-M200+2Hf

Hf lowers the incipient melting temperatureof superalloy. As carbon content in Hf-bearingalloy decreases, the incipient melting temperaturedrops furthey. PD ingots have stronger tendencyto incipient melting than HRS ones. Even thoughin PD ingot, the sensitivities at both endsof the ingot are quite different. The meltingof Ni_5Hf phase may be considered as one of themain factors affecting incipient melting. Themore Ni_5Hf the alloy contains, the more seriousthe incipient melting becomes. The results ofdifferential thermal analysis (DTA) have provedthat the peak of 1135-1160℃ corresponds tothe melting range or Ni_5Hf. By means of apretreatment at 1150℃, 8h, Ni_5Hf phase can beeliminated in two ways: the reactionNi_5Hf+γ(C)→MC_(2)+γ and solid solution, andtherefore the final solid solution treatmentcan be carried out at 1260℃. This brings abouta high homogenized structure and further increasesthe stress rupture properties of the alloy at1040℃, 140 MPa.     

影响含Hf定向凝固合金初熔的某些因素

含Hf的镍基高温合金存在Ni_5Hf相,它是影响合金初熔的主要因素之一。当该相的量大于1.0v-%时,在加热示差热分析(DTA)曲线上的1135-1160℃处出现Ni_5Hf相的熔化峰。P.D法定向铸锭上、下端存在明显的Ni_5Hf偏析,因而对初熔的敏感性明显不同。Ni_5Hf相的初熔促进了共晶γ′和M_3B_2的熔化。低碳与无碳含Hf合金的初熔倾向更大,缓冷组织和固溶处理的升温速度对初熔是敏感的。高于3V-%的初熔量将会降低合金的持久强度,其断裂主要沿Ni_5Hf初熔区和共晶γ′之间的界面扩展。采用1150℃8h预处理能消除全部的Ni_5Hf相,有效地控制含Hf合金的初熔。     

定向工艺和铪含量对一种镍基高温合金的影响

本文采用两种定向凝固工艺即功率下降(P.D)法和快速凝固(H.R.S)法研究了不同Hf含量对一种镍基高温合金组织和性能的影响。实验结果表明,加入合金中的Hf主要偏析在枝晶间和γ/γ′共晶相内;合金加Hf后,显微组织发生明显变化:γ/γ′共晶相大量增多,其形态也发生明显变化;晶界和枝品间状态得到改善;出现了几种新的富Hf微量相。合金760℃持久性能(特别是横向性能)随Hf含量的增加显著提高。但1040℃的持久寿命却随Hf含量的增加而下降。采用H.R.S工艺时合金的中、高温性能均明显优于P.D法工艺。 文中讨论了合金加Hf后组织和性能变化的机理,确定了本合金较合适的含Hf量为1.0～2.0％(重量),并认为应优先采用H.R.S定向工艺。     

FACTORS INFLUENCED INCIPIENT MELTING IN Hf-BEARING DS Ni-BASE SUPERALLOYS

含Hf的镍基高温合金存在Ni_5Hf相,它是影响合金初熔的主要因素之一。当该相的量大于1.0v-％时,在加热示差热分析(DTA)曲线上的1135-1160℃处出现Ni_5Hf相的熔化峰。P.D法定向铸锭上、下端存在明显的Ni_5Hf偏析,因而对初熔的敏感性明显不同。 Ni_5Hf相的初熔促进了共晶γ′和M_3B_2的熔化。低碳与无碳含Hf合金的初熔倾向更大,缓冷组织和固溶处理的升温速度对初熔是敏感的。 高于3V-％的初熔量将会降低合金的持久强度,其断裂主要沿Ni_5Hf初熔区和共晶γ′之间的界面扩展。采用1150℃8h预处理能消除全部的Ni_5Hf相,有效地控制含Hf合金的初熔。     

ISP-2/Ⅲ-DS真空定向凝固炉已正式投入使用

六二一所从西德引进的这台设备,经机动部门和铸造研究室共同努力,在没有外国技术人员参加的情况下,依靠自己的力量,克服了各种困难,已经安装调试完毕(图1),各项性能达到设备规定的指标。不仅为国家节约了几万元外汇,而且培养锻炼了有关技术人员。     

DirectionaHy Solidified High-strength Superalloy DZ22

Alloy DZ22 possesses rather high intermediateand elevated temperature mechanical propertiescomparable with the advanced commercial DS al-loy PWA1422.The alloy composition is based onPWA1422 alloy,only the content ranges of Hf,Cand Zr are changed for systematic study.The pres-ent melting technology for master alloy ingot andDS process parameters for components are suitablefor this alloy.The alloy revert which has     

固溶处理对DZ22合金组织和性能的影响

一、前 言 DZ22合金是定向凝固镍基高温合金,具有较高的中、高温持久性能。但按照现行热处理制度(1205℃/2h,AC+870℃/32h,AC)处理后,合金的高温持久性能与铸态相比,提高的幅度不大,有时甚至与铸态相当。这说明热处理工艺没有充分发挥作用。近年来,国内外的定向凝固和单晶合金的研究者,一致提出采用尽可能高的固溶温度,并用试验数据证实其好处。本文对DZ22合金进行了固溶温度影响的试验,为改进现行热处理制度提供了必要的依据。     

两种定向凝固方法DZ22合金的力学性能和组织

比较了超高梯度定向凝固法（ＺＭＬＭＣ法）和普通定向凝固法（ＨＲＳ法）对ＤＺ２２合金的高温力学性能和组织的影响。结果表明：ＺＭＬＭＣ法大幅度地提高了合金的高温力学性能，９８０℃，２２０ＭＰａ条件下的高温持久寿命由７２ｈ提高到１６８ｈ；一次、二次枝晶臂间距λ１和λ２分别由１５０ｕｍ和５０ｕｍ左右到减小到６８ｕｍ和１６ｕｍ左右；元素的枝晶偏析得到抑制；合金显微组织的组成相ｒ’，（ｒ＋ｒ’）共晶，ＭＣ型碳     

Influence of Solution Temperature on Microstructure and Mechanical Properties of Directionally Solidified Superalloy DZ22

The microstructure changed markedly withincreasing solution temperature, i.e eutecticγ' phases and coarse primary γ' phase areredissolved continuously into matrix, whichwas finished at 1250-1260℃, and more and finerγ' phases are reprecipitated. The grain boundarymorphology changed gradually to "fine line"form. The dendritic segregation of elementsdecreased. With raising solution temperaturethe longitudinal stress-rupture life at highand intermediate temperature were enhanced,but the transversal stress-rupture life atintermediate temperature decreased obviously.The incipient melting temperature of DZ22 alloywas measured to be 1230-1240℃ and may beincreased by homogenization at 1150℃. In thispaper the principle of determining solutiontemperature of DS alloys was discussed. Itwas suggested that the solution temperatureof alloy DZ22 selected at 1200-1210℃ is appropri-ate.