热处理工艺对高锰钢组织和硬度的影响

本文研究了水韧处理和时效处理对高锰钢组织和硬度的影响,采用激光共聚焦显微镜和X射线衍射仪（XRD）对其组织进行分析,采用显微硬度计测试其维氏硬度值。研究结果表明：水韧处理后的组织为奥氏体和少量的碳化物,当保温时间较短时,碳化物固溶不完全,随着保温时间的延长,碳化物完全溶解,奥氏体晶粒发生长大;相较于铸态组织硬度HV 461.6,水韧处理后组织硬度降到HV 229.9。随着时效温度的升高和保温时间的延长,首先会在奥氏体晶界处析出针状碳化物,然后这些针状碳化物会向晶粒内部长大,同时会在晶界处析出点状碳化物;随着时效温度的升高,显微硬度值逐渐增大,且在显微组织发生明显改变时,试样的显微硬度发生突增;当保温时间由1 h增至3 h时,试样的显微硬度值大都有所增加,但当时效温度为300℃和350℃时,试样的显微硬度值相差不大。     

一种高Mo镍基高温合金碳化物析出及退化转变规律研究

试验研究了一种高Mo镍基高温合金在不同温度下晶界碳化物的析出情况。结果表明,在高于1 000℃保温处理1 h,晶界上析出颗粒状碳化物,主要为富Mo、Ti的M_6C型碳化物;当温度低于1 000℃时,晶界析出棉絮状碳化物,主要为富Cr、Mo的M_(23)C_6型碳化物。另外,试验结果表明,在一定温度下保温处理,MC碳化物会退化转变为M_6C,这主要与合金中Mo含量高有关。     

预氮化对Cr-Co-Mo-Ni轴承钢渗碳层组织和性能的影响

化学热处理工艺对轴承钢的服役性能具有重要影响。研究了预氮化工艺对新型Cr-Co-Mo-Ni轴承钢渗碳层组织和性能的影响规律。结果表明,经预氮化处理的渗碳层组织可划分为析出物和针状马氏体区,析出物、针状马氏体和板条马氏体混合区,以及析出物和板条马氏体区,且在原渗氮形成的白亮层位置有数量较多的微小孔洞出现。预氮化全工艺试样表层含铬碳化物析出较少,随渗层深度的增加,次表层析出较多的含铬碳化物且尺寸较大。相较于仅渗碳试样,在表层相同位置,经预氮化处理的试样在回火后,析出物的尺寸更细小。预氮化能够提高渗碳效率,增加渗层硬度,在全工艺试样渗层深度为0.12~0.82 mm,预氮化试样的硬度高于仅渗碳试样,且经渗后热处理的硬度增加程度也显著高于仅渗碳试样。     

Co-Al-W三元合金热处理组织

研究不同Al和W含量对四种Co-Al-W三元合金的初熔温度、热处理组织和硬度的影响.结果表明:四种Co-Al-W三元合金的固、液相点温度均超过镍基单晶高温合金液相点温度;在1300℃/8h固溶处理后,三种合金均仅得到γ(fcc)单相组织,而高W合金在晶界和晶内均有μ相Co₇W₆析出;在800℃/100h和900℃/50h时效处理后,四种合金在基体γ相中均析出Ll₂型γ'相Co₃(Al,W),其γ+γ'两相组织形貌与镍基高温合金相似;高W(12%)和高Al(12%)合金分别促进了μ相Co₇W₆和富Al相析出.综合以上结果并结合时效合金的硬度结果,初步确定了含γ+γ'两相组织的合金成分范围.     

GH220合金中晶界针状碳化物的成因

研究了镍基高温合金在1123K,392MPa下周期持久断裂过程中晶界针状碳化物的析出过程。分析了它的形成原因,实验采用二种热处理工艺,得到二种不同的晶界状态:直晶和弯晶。透射电镜分析结果表明,无论何种晶界状态,晶界碳化物都有一个由颗粒状碳化物向针状碳化物转化的过程。而弯晶处理的合金,首先发生由弯晶向平直晶界的转变,即尺寸较大且不规则状的晶界碳化物逐渐断裂成颗粒状排列的晶界碳化物,该过程所需时间较长,这就解释了弯晶合金比如直晶合金针状碳化物量少的原因。提出了一个由颗粒状碳化物向针状碳化物转化的模型。     

GH1016合金高温状态下晶界的强化与韧化

本文对GH1016合金750℃高温状态下晶;界状态进行了研究,决定该合金750℃高温塑性关键在于晶界碳化物形貌及M6C量多少,并阐述了该合金晶界碳化物转化机理及两种在晶界产生颗粒链状M6C碳化物途径：一是合金本身中控制一定量的微量残Ca、Mg;二是等温热处理工艺。     

时效处理对Cr20Ni32AlTi合金室温冲击性能的影响

 研究了铁镍基耐热耐蚀合金Cr20Ni32AlTi在1150℃、15min固溶处理并经450~850℃、05~5h的时效处理后室温冲击性能的变化规律。结果表明,450℃时效冲击性能最好。随时效温度升高,时效时间延长,冲击性能下降。450~850℃时效时,在合金晶界上有碳化物M23C6析出,且随温度增加和时间延长,析出增加。850℃时冲击功最低,此时碳化物M23C6析出相呈连续颗粒状析出,布满整个晶界。且观察到一些部位碳化物M23C6析出相形成薄膜,冲击时因基体变形而脆断成条块状。     

热处理工艺对GH4169合金组织和性能影响

通过三种不同热处理工艺对GH4169合金进行处理。通过金相观察、扫描电镜、显微硬度和冲击试验,观察和研究了三种不同热处理工艺下GH4169合金的微观组织演变和力学性能。结果表明:三种不同的热处理工艺改变了GH4169合金中δ相的析出以及分布。经过HST处理后,δ相呈短棒状或粒状在晶界上析出;通过ST处理后在晶界和晶内可获得较多的δ相;而通过DA处理的微观组织晶界处较平滑,几乎没有δ相析出。经过HST和ST处理后,GH4169合金的硬度值变化不大,冲击强度明显提高,断裂方式表现为穿晶断裂。通过DA处理后,其硬度降为热轧态的60%,但是冲击强度提高了4.5倍,断裂方式表现为沿晶断裂。     

低温回归再时效对7B04-T651铝合金厚板组织与性能的影响

研究了回归及回归再时效处理对7B04铝合金预拉伸厚板的显微组织、力学性能及电导率的影响.通过透射电子显微镜(TEM)观察了回归再时效合金的微观组织,并对合金进行了力学性能及电导率测试.结果表明:采用合适的回归再时效工艺(180℃/1h,水淬+120℃/22h)可使材料具有接近T6态合金强度的同时,电导率大幅度提升,达21.0MS·m^-1;此时,合金晶内组织与T6状态相似,析出相细小呈弥散分布,而晶界组织与双级T74时效组织特征相似,晶界析出相粗大呈不连续分布,晶界两侧伴之以明显的晶界无析出带.     

GH4710合金的相析出特征及其与热加工塑性损伤的关联性

利用Thermal Calc热力学软件、光学金相显微镜、扫描电镜等手段分析了GH4710合金原始态和不同条件热物理模拟变形后的析出相及加工损伤特征,系统研究了析出相特征与该合金热加工塑性损伤及开裂的关联性.结果表明：GH4710合金的原始组织主要由γ'、MC及M₂₃C₆碳化物、γ+γ共晶组织组成;热加工时微孑洞等损伤在MC碳化物及γ+γ共晶组织处形核后沿晶界扩展,最终相互连接导致合金大面积破坏;γ'相优先在MC碳化物及共晶组织附近析出,并通过其共格应力场的作用增加了损伤形核和扩展阻力,使合金在较低温度下的塑性损伤值明显小于高温条件下.     

Microstructure Evolution of a Simulated Coarse-Grained Heat-Affected Zone of T23 Steel During Aging

In this work, simulated CGHAZ of T23 steel was produced via a thermomechanical simulator, and then the CGHAZ specimens were aged at 650 °C for 0 to 240 hours to simulate the microstructure evolution of as-welded CGHAZ during service. Microstructure change and carbide precipitation were observed by OM, SEM, EBSD and TEM + EDS. Carbide precipitation kinetics in T23 steel at 650 °C was calculated for comparison with the experiment results. The hardness change of CGHAZ during aging was detected, and the effect of microstructure evolution on hardness was analyzed. The results showed that the CGHAZ of T23 steel exhibited a mixed microstructure of martensite and bainite with high hardness in as-welded condition. After aging at 650 °C, the microstructure recovered, recrystallization occurred, the dislocation density decreased, and the lath width increased. Consequently, the hardness dropped, the drop depending on the aging time. In the early stage of aging (before 24 hours), the precipitations inside the grain were mainly M3C, M7C3 and a small number of M23C6 carbides, while the precipitation at the grain boundaries was M23C6. The precipitation of M23C6 caused the hardness to drop rapidly. When aged for 24 to 48 hours, MX precipitated inside grains extensively. The precipitation hardening produced by MX could slow down the decline of hardness. As the aging proceeded, carbide precipitated and transformed as follows: M3C → M3C + M7C3 + M23C6 → M3C + M7C3 + M23C6 + MX → M23C6 + MX + M6C. W-rich carbides precipitated in some grain boundaries of CGHAZ during aging, which may be related to the W segregation at those grain boundaries.     

Grain growth and carbide precipitation in superalloy, UDIMET 520

The results of an experimental study on the grain coarsening behavior, M₂₃C₆ carbide precipitation, and secondary MC carbide precipitation kinetics in UDIMET 520 are presented. Primary MC carbides and M (C, N) carbonitrides strongly influence the grain growth, with their dissolution near 1190 °C and 1250 °C, respectively, resulting in two distinct grain coarsening temperatures (GCTs). M₂₃C₆ carbides precipitate in the alloy over a wide range of temperatures varying between 600 °C and 1050 °C. A discrete M₂₃C₆ grain boundary carbide morphology is observed at aging temperatures below 850 °C. Secondary MC carbides formed at temperatures ranging between 1100 °C and 1177 °C, in specimens in which primary MC dissolution had been obtained at solution treatment temperatures of 1190 °C to 1250 °C. A schematic time-temperature-transformation (TTT) diagram for understanding the microstructure and precipitation inter-relationships in UDIMET 520 alloy is also presented.     

Chromium depletion in the vicinity of carbides in sensitized austenitic stainless steels

The analytical electron microscope (AEM) was used to examine the microstructure of type 316LN stainless steel alloys which had been annealed for 50 to 300 hours in the temperature range 600 to 700 °C. The M₂₃C₆ carbide chemistry and distribution are described as a function of heat treatment.X-ray spectroscopy in the AEM revealed significant chromium depletion at grain boundaries in the vicinity of carbides for samples aged at 50 and 100 hours at 650 °C and 100 and 300 hours at 700 °C, with lower grain boundary chromium values observed at 650 °C than at 700 °C. The width of the chromium depleted zone normal to the grain boundaries increased with increasing annealing time and/or temperature. Measurements of chromium concentration along the grain boundaries away from a carbide were made after aging at 700 °C for 100 hours, and the chromium level rose steadily until the bulk value was reached at a distance of ~3μm from the carbide. The width of the chromium depleted zone normal to the boundaries in the same sample was an order of magnitude less. Some molybdenum depletion was also found at the grain boundaries, and the Mo-depletion profiles were in form and extent similar to the chromium results. Simple thermodynamic models were used to calculate the equilibrium value of chromium at the carbide-matrix interface, and the chromium distribution along and normal to the grain boundaries. The results of these models agreed well with the AEM results, and the agreement can be improved by considering the effect of electron probe configuration on the AEM measurements. The calculated thermodynamic data and the AEM results were related to the corrosion behavior of the alloys. The occurrence of severe asymmetries in some concentration profiles normal to the grain boundaries, which increased with increasing annealing temperature or time, was shown to be due to boundary movement during the discontinuous precipitation of M₂₃C₆ carbides.     

The microstructural response of mill-annealed and solution-annealed INCONEL 600 to heat treatment

Samples of INCONEL* 600 were examined in the mill-annealed and solution-annealed states, and after isothermal annealing at 400 °C and 650 °C. The corrosion behavior of the samples was examined, analytical electron microscopy was used to determine the microstructures present and the chemistry of grain boundaries, and Auger electron spectroscopy was used to measure grain boundary segregation. Samples of different alloys in the mill-annealed state were found to have quite different microstructures, with Cr-rich M₇C₃ carbides occurring either along grain boundaries or in intragranular sheets. The corrosion behavior of the samples correlated well with the occurrence of grain boundary chromium depletion. Solution annealing at 1190 °C caused dissolution of all carbides, whereas at 1100 °C the carbides either dissolved or the grain boundaries moved away from the carbides, depending upon alloy carbon content. Low-temperature annealing at 400 °C had little effect on millannealed or fully solutionized samples, but in samples with intragranular carbides present, the grain boundaries moved until intersecting or adjacent to the carbides. Isothermal annealing at 650 °C caused carbide nucleation and growth at grain boundaries in fully solutionized samples. Chromium depletion at grain boundaries accompanied carbide precipitation, with a minimum chromium level of 6 wt pct achieved after 5 hours. Healing was found to occur after 100 hours. Solution-annealed samples with intragranular carbides present had more rapid corrosion kinetics since the grain boundaries moved back to the existing carbides. Thermodynamic analysis of the chromium-depletion process showed good agreement with experimental measurements. The Auger results found only boron present at grain boundaries in the mill-annealed state. Aged samples had boron, nitrogen, and phosphorus present, with phosphorus and nitrogen segregating to the greatest extent. The kinetics of phosphorus segregation are much slower at 400 °C compared with 650 °C.     

Nimonic 80A合金螺栓的组织织构及高温应力松弛行为

利用SEM与EBSD技术研究Nimonic 80A高温合金螺栓的组织织构特点,并对不同温度下的高温应力松弛行为及组织织构演变进行分析。结果表明,合金中γ相组织未形成显著织构,晶粒取向择尤情况与晶粒尺寸无对应性。合金中第二相主要为γ′相与Cr的碳化物,γ′相在基体中弥散分布,而Cr的碳化物分别在晶界析出和沿螺栓轴向“链状”分布,其分布特征与γ晶粒组织及取向无显著关联性。应力松弛前后,晶粒组织、碳化物分布及织构均无明显变化,但γ′相发生了一定的粗化。载荷一定时,温度对应力松弛行为存在显著影响,即较高温度下样品的应力松弛率较高。较高温度下位错滑移更易开动,与样品中更多晶粒表现出较高晶粒取向散布(GOS)值相对应,但各晶粒GOS值的高低未表现出晶粒取向与晶粒尺寸依赖性。     

Microstructural evolution and mechanical properties of a new Ni-based heat-resistant alloy during aging at 750℃

Microstructural evolution and mechanical properties of a new candidate Ni-based heat-resistant alloy for advanced ultra-supercritical( A-USC) steam turbine rotors were investigated during aging at 750 °C up to 10 000 h. The evolutions of γ' particles inside austenitic grain and M_(23)C_6 carbides along grain boundaries were characterized according to their morphologies,distributions,and growth kinetics. Mean radius of the γ' spherical particles grew from 20. 3 to 90. 0 nm after aging for 10 000 h,and the corresponding coarsening behavior was conformed to the law of Lifschitz-Slyosovd-Wagner( LSW). The weight fraction of γ' particles slightly increased from 10. 0 to 12.0wt. % after aging of long duration at 750 ℃. The Cr-rich M_(23)C_6 carbides discontinuously precipitated along grain boundaries,while other detrimental phases were not formed during the aging treatment,and hence the strength of grain boundary was enhanced by these discontinuously distributed carbides. The critical size of γ' had a direct influence on the maximum hardness of this alloy. Moreover,this alloy presented a good impact toughness for the safety after long time aging at high temperature.     

钼钨钒合金化热作模具钢高温回火组织演变

为适应热冲压技术的发展需求,开发了一种新型高热导率高耐磨性能热冲压用模具钢材料。采用扫描电镜（SEM）、透射电镜（TEM）等检测手段对钼钨钒合金化新型模具钢的高温回火性能与组织特征进行了研究。阐明了新型热冲压模具钢回火过程碳化物析出与演变规律。实验结果表明:实验用钼钨钒合金化模具钢材料具有良好的回火二次硬化性能,在500～600 ℃温度区间回火时,回火组织硬度上升;在600 ℃回火出现二次硬化峰值;当回火温度超过600 ℃后,组织软化程度明显,回火硬度开始下降。实验模具钢在高温回火过程中的硬度变化与其合金碳化物的偏聚、析出和聚集长大密切相关。当在560 ℃以下回火时,实验钢组织中未有合金碳化物析出;当回火温度大于560 ℃时,回火组织中开始析出M₂C型碳化物;当回火温度高于600 ℃后开始析出MC型碳化物;当在620 ℃长时间回火后M₂C型碳化物转化为M₆C型碳化物,此时实验钢硬度开始明显下降;而当回火温度高于660 ℃时,新型实验钢组织中主要为M₆C和MC型合金碳化物。      

固溶处理对GH2036合金组织和硬度的影响

利用光学显微镜、扫描电镜、布氏硬度仪等研究了GH2036合金Φ150 mm棒材在1120~1240 ℃固溶处理的组织演化和硬度变化规律。研究表明,GH2036合金锻后空冷锻材组织中主要存在富Cr和Nb-V两种类型的碳化物,在1220 ℃固溶处理后碳化物大部分回溶,晶粒尺寸基本均匀。合金HB硬度值随热处理温度的升高而降低,但在1160~1200 ℃处理时,硬度随温度的升高,HB硬度值由185升至193,这主要与碳化物大幅度向基体回溶有关。     

长期时效对低碳Ni-Cr-W-Mo耐热合金组织和力学性能的影响

 研究了长期时效对低碳Ni-Cr-W-Mo耐热合金组织和力学性能的影响。结果表明,长期时效后低碳Ni-Cr-W-Mo耐热合金存在3种析出相：M6C型初生碳化物相、二次M23C6型碳化物相和μ相;其中M6C型初生碳化物相存在于供应态和时效态。因为合金含碳量低,所以合金在750℃时效超过200h和在900℃时效超过100h时,就析出μ相。合金在750℃时效至1000h时,随着时效时间的延长,合金硬度值不断增加;而合金在900℃时效至1000h时,随着时效时间的延长,合金硬度值首先增加至最大值,随后合金硬度值随着时效时间的延长而降低;这是因为二次M23C6型碳化物析出形态在时效过程中发生了变化。合金时效前后的室温拉伸性能数据证实微量μ相对合金室温拉伸影响很小。     

C700R-1耐热合金700℃时效组织和性能演变

研究了新型汽轮机转子用C700R-1耐热合金700℃长期时效组织和性能的演变.研究表明：合金的主要析出相为 M23 C6、MC、γ′.C700R-1合金长期时效组织结构稳定,时效5000 h 晶界处 M23 C6碳化物平均宽度从190 nm增加至240 nm,呈不连续状态分布;时效5000 h球形γ′平均直径从22．0 nm粗化至49.8 nm,粗化速率缓慢.合金拉伸强度和硬度随时效时间延长先快速升高,后缓慢降低,并逐渐趋于稳定;理论计算 C700R-1合金中γ′临界尺寸为29.8 nm;长期时效后合金的冲击值在50 J 以上.