EFFECT OF VACUUM HEAT TREATMENT ON OXIDATION BEHAVIOR OF SPUTTERED NiCrAlY COATING

A bond coat for thermal barrier coating (TBC), NiCrAlY coating, is subjected to vac-uum heat treatment in order to remove internal stress before ceramic top coat is de-posited. The effect of vacuum heat treatment on the oxidation behavior of the sputtered NiCrAlY coating has been investigated. The as-sputtered NiCrAlY coating consists of γ-Ni and b-NiAl phases. After vacuum heat treatment, the sputtered NiCrAlY coating mainly consists of γ'-Ni3Al, β-NiAl, γ-Ni, and trace of α-Al2O3 phases. The isothermal oxidation of sputtered NiCrAlY coating with and without vacuum heat treatment has been performed at 1000℃. It is shown that a-Al2O3 formed during vacuum heat treatment acts as nuclei for the formation of a-Al2O3, and the protective a-Al2O3 scale is formed more rapidly on the vacuum heat treated NiCrAlY coating than that formed on the untreated coating. Also the a-Al2O3 scale has a better adherence to the vacuum heat treated NiCrAlY coating. Therefore the vacuum heat treatment improves the oxidation resistance of sputtered NiCrAlY coating.

Effect of vacuum heat treatment on microstructure and microhardness of cold sprayed Cu-4Cr-2Nb alloy coating

The effect of vacuum heat treatment on the microstructure and microhardness of cold-sprayed Cu-4%Cr-2%Nb alloy coating was investigated. The heat treatment was conducted under the temperatures from 250 ℃ to 950 ℃ with a step of 100 ℃ for 2 h. It was found that a dense thick Cu-4Cr-2Nb coating could be formed by cold spraying. After heat treatment, a Cr2Nb phase was uniformly distributed in the matrix, which was transferred from the gas-atomized feedstock. A little grain growth of Cr2Nb phase was observed accompanying with the healing-up of the incomplete interfaces between the deposited particles at the elevated temperatures. The coating microhardness increases a little with increasing the temperature to 350 ℃, and then decreases with further increasing temperature up to 950 ℃. This fact can be attributed to the microstructure evolution during the heat treatment.

Numerical Simulation of Vacuum Heat Treatment Thermal Hysteresis Time of GH4169 Superalloy Workpiece

A nonlinear finite element model of vacuum heat treatment process was developed. In this model, influence of many factors, such as nonlinear heat radiation, temperature-dependent thermal physical properties of material are considered. The temperature field of GH4169 alloy workpiece during vacuum heat treatment process was calculated using finite element software MSC.Marc, and the thermal hysteresis time of the workpiece was predicted. An experiment of vacuum heat treatment of GH4169 superalloy workpiece was carried out to verify the calculation. The experimental results of temperature profile agree well with the simulated results. This work lays a theoretical foundation for optimizing technical parameter of vacuum heat treatment process.

Flexible Furnace Concepts for Vacuum Heat Treatment Combined with High-pressure Gas Quenching

IN the past five years the process combination of vacuum hardening, respectively vacuum carburizing with high-pressure gas quenching was successfully introduced to the market, especially in the manufacture of gears. In the meantime furnace concepts for various applications are available to the industry. In the following report three plant varieties are introduced, which differ in process flexibility and throughput. This report also explains criteria for the selection of a furnace in view of the existing application requirements. Besides this a short introduction is given into the vacuum carburizing process and the high-pressure gas quenching technology.

Influence of vacuum heat treatment on structure and micro-hardness of electroless Ni-P-SiC composite coating

The electroless Ni-P-SiC composite coatings were prepared and the influence of vacuum heat treatment on its structure and properties was analyzed. The Ni-P-SiC composite coatings were characterized by morphology,structure and micro-hardness. The morphology and structure of the Ni-P-SiC composite coatings were studied by scanning electron microscopy(SEM) and X-ray diffractometry(XRD),respectively. A great deal of particles incorporation and uniform distribution were found in Ni-P-SiC composite coatings. XRD results show a broad peak of nickel and low intensity SiC peaks present on as-deposited condition. Micro-hardness of as-deposited Ni-P-SiC composite coatings is improved greatly,and the best micro-hardness is obtained after heat treatment in a high vacuum at 400 ℃ .

Effect of vacuum heat treatment on microstructure and corrosion behavior of HVOF sprayed AICoCrFeNiCu high entropy alloy

To improve the corrosion resistance of coalbed methane drilling equipment,an AICoCrFeNiCu high entropy alloy coating was prepared on the AISI 4135(35CrMo)steel substrate by high velocity oxygen fuel(HVOF)technology,and the coating was subjected to vacuum heat treatment(VHT)at different temperatures(500,700,900 and 1100℃).The corrosion test of the substrate and the coatings after VHT in coalbed methane drilling fluid was carried out.The results show that the HVOF sprayed AICoCrFeNiCu high entropy alloy(HEA)coating has a good bonding with the substrate,and the porosity of the coating is about 2.4%.There is partial segregation in the coating,and the coating mainly consists of body-centered cubic phase.The coating has good thermal stability,and the phase structure and microstructure of the coatings have changed after VHT at different temperatures.Compared with the substrate,the as-sprayed coating has better uniform corrosion resistance,and the corrosion resistance of the coating after VHT is further improved.After VHT at 500℃,the HVOF-sprayed AICoCrFeNiCu HEA coating has the best corrosion resistance.

Influence of laser re-melting and vacuum heat treatment on plasma-sprayed FeCoCrNiAl alloy coatings

FeCoCrNiAl high entropy alloy coatings were prepared by supersonic air-plasma spraying.The coatings were post-treated by vacuum heat treatment at 600 and 900°C,and laser re-melting with 300 W,respectively,to study the influence of different treatments on the structure and properties of the coatings.The phase constitution,microstructure and microhardness of the coatings after treatments were investigated using X-ray diffraction,scanning electron microscopy and energy dispersive spectrometry.Results showed that the as-sprayed coatings consisted of pure metal and Fe-Cr.The AlNi;phase was obtained after the vacuum heat treatment process.A body-centered cubic structure with less AlNi;could be found in the coating after the laser re-melting process.The average hardness values of the as-sprayed coating and the coatings with two different temperature vacuum heat treatments and with laser re-melting were 177,227,266 and 682 HV,respectively.This suggests that the vacuum heat treatment promoted the alloying process of the coatings,and contributed to the enhancement of the coating wear resistance.The laser re-melted coating showed the best wear resistance.

Synergistic effects of composition and heat treatment on microstructure and properties of vacuum die cast Al-Si-Mg-Mn alloys

The purpose of this study was to prepare high-quality Al-Si-Mg-Mn alloy with a good combination of strength and ductility employing the vacuum-assisted high-pressure die cast process. An orthogonal study of heat treatments was conducted to design an optimized T6 heat treatment process for both Al-10%Si-0.3%Mg-Mn and Al-11%Si-0.6%Mg-Mn alloys. The results demonstrate that no obvious blisters and warpage were observed in these two alloys with solid solution treatment. After the optimal T6 heat treatment of 530°C×3 h + 165°C×6 h, Al-11%Si-0.6%Mg-Mn alloy has better mechanical properties, of which tensile strength, yield strength and elongation reached 377.3 MPa, 307.8 MPa and 9%, respectively. The improvement of mechanical properties can be attributed to the high density of needle-like β″(Mg_5Si_6) precipitation after aging treatment and the fine and spherical eutectic Si particles uniformly distributed in the α-Al matrix.

Studies on Preparation of Onion-like Fullerenes by Vacuum Heat-treatment

Onion-like Fullerenes were produced at high-temperature in vacuum. The morphology of the carbon nano onion-like fullerenes was examined and characterized by high-resolution transmission electron microscopy (HRTEM). It can be seen that the nano-sized, onion-like fullerenes possess high degree of graphization. The results suggested that the catalyst is the main factor affecting the size and yield of the fullerenes. The method is very promising for simple mass production.

The Integration of Vacuum Brazing into Heat Treatment - A Progressive Combined Process

The continuous constructive challenge to improve the functionality and efficiency of components always results in higher demands on production engineering, against the background of the generally increasing cost pressure. In many cases, you will just succeed in producing competitive and innovative products by combining and coupling of different procedures to an independent (hybrid) technology. The use of hybrid procedures for metal joining and heat treatment of metallic materials finds more and more industrial fields of application. Modern vacuum lines with integrated pressurized gas quenching are considered high-performance and flexible means of production for brazing and heat treatment tasks as well in the turbine industry as in the mould making and tool manufacturing industry. In doing so, the heat treatment is coupled with the brazing cycle in a combined process so that the brazing temperatures and soak times are adapted to the necessary temperatures and times for solution heat treatment and austeniting. This user-oriented article describes on the one hand examples of brazing of turbine components, but above all the practical experience from the plastics processing industry, where the requirement for a high-efficient cooling of injection moulding dies gains more and more importance. The combined procedure "Vacuum Brazing and Hardening" offers plenty of possibilities to produce mould inserts with an efficient tempering system in an economic way.

Vacuum Furnace - Integrated“Sub zero” Treatment

The vacuum heat treatment with overpressure gas quenching is more and more accepted due to considerable advantages compared to the traditional oil and salt bath processes. Continuous further developments and new concepts like multi-directional cooling systems, a separate quenching chamber and "sub zero" systems lead towards an oxidation free and low distortion vacuum heat treatment for a broad range of parts and materials. Short and energy saving processes guarantee a high economic efficiency and environmental compatibility. The "sub zero" system which is integrated into the standard vacuum furnace achieves a heat treatment result with a high conversion of retained austenite in fully automatic hardening and tempering processes.

Application of improved vacuum degassing technique to refinement of heat resistant steel P91

An effective vacuum melting technique based on the improved vacuum degassing technique was used to produce thick-walled seamless pipes of 9Cr-1Mo-V-Nb-N martensitic heat resistant steels in order to reduce the contents of harmful impurity such as oxygen, phosphorus. Then the pipe was heat treated by using optimized process technique. Both static and dynamic mechanical properties at room temperature and 566℃ were measured respectively and evaluated by means of comprehensive analysis of standard deviation and statistic test. The results show that the comprehensive mechanical properties of this pipe are much better than those of pipes untreated with the improved vacuum degassing technique and heat-treated by using original heat-treatment process and almost the same as those of imported P91 thick-walled seamless steel pipe.

真空热处理对落叶松木材纤维素形貌及结构的影响

以我国东北主要用材树种落叶松木材为研究对象,采用真空热处理方法对其材质进行改良,探究其纤维素形貌及结构热响应机制。采用湿化学法提取未处理和不同真空热处理条件下(180~220℃温度范围,处理6 h)落叶松木材纤维素,利用扫描电子显微镜观察其形貌,X射线光电子能谱和X射线衍射仪分析其化学结构及结晶度变化。结果表明:未处理木材提取的纤维素呈棒状且表面有序平行结构,热处理后木材纤维素变弯曲且表面呈扭曲结构,并随热处理温度升高,纤维素表面扭曲越显著。由X射线光电子能谱分析,随热处理强度增加,纤维素O/C比值由未处理材65.5%降低至59.5%,并且C1含量增加、C2和C3分别降低,表明热处理木材提取的纤维素碳链缩短,并且其表面存在半纤维素以及热处理过程中木质素与碳水化合物缩聚反应形成的木质素-碳水化合物。随热处理温度提高,纤维素结晶度增加,同时纤维素中Ⅱ型占比提高、Ⅰ型降低,并且二者晶胞结构和分子基团构象存在差异,进而导致热处理前后木材提取的纤维素形貌结构不同。研究结果有助于深入理解木材化学成分热响应特性,为优化真空热处理改性木材工艺提供理论依据。

FV520B钢叶轮的真空热处理

对FV520B钢试样和叶轮在真空炉中进行了1050℃加热随后炉冷至850℃,再在通入氮气的真空炉中冷却至50℃空冷的固溶处理,在真空炉中在850℃加热随后在充入氮气的真空炉中冷却至50℃空冷的调整处理,以及在真空炉中603℃时效处理。热处理后检测了叶轮的力学性能、显微组织和坐标尺寸。结果表明:叶轮的力学性能和坐标尺寸均符合要求,显微组织由回火马氏体、奥氏体和弥散分布的析出相组成,对FV520B钢叶轮进行真空热处理是可行的。

模具真空热处理

热处理是保证模具性能和寿命的关键环节,真空热处理具有无氧化、无脱碳、可脱脂脱气、表面质量好和热处理变形小等优点,广泛应用于模具的热处理。首次修订的标准GB/T 22561—2023真空热处理规定了金属材料在真空状态下热处理设备、工艺过程与工艺规范等要求,有利于指导和规范模具真空热处理生产,提高模具质量,推动我国模具工业高质量发展。

Cu含量和热处理工艺对Al-Si-Mg-Mn-xCu铸造铝合金显微组织和力学性能的影响

采用三维X射线显微镜、光学显微镜、扫描电子显微镜、透射电子显微镜及硬度测试系统研究Cu含量及热处理工艺对真空压铸Al-Si-Mg-Mn-xCu合金显微组织和力学性能的影响。研究发现,虽然Cu含量增加会提高铸锭中气孔的密度和尺寸,但是Cu添加将促进凝固过程中含Cu初生相(Q-Al_(5)Cu_(2)Mg_(8)Si_(6)和θ-Al_(2)Cu)的形成,从而提高合金性能。合金中形成5种不同结构的初生相,包括共晶Si、α-Al(Fe,Mn)Si、β-Mg_(2)Si、Q-Al_(5)Cu_(2)Mg_(8)Si_(6)和θ-Al_(2)Cu相。随着Cu含量增加,θ相的面积分数迅速增加,α-Al(Fe,Mn)Si相面积分数首先降低,随后缓慢增加,而Q相的变化趋势与α-Al(Fe,Mn)Si相相反。这些初生相在热处理过程中会出现不同的演变规律。在随后的时效处理过程中,Q'和θ'相的协同析出能显著提高合金的时效硬化潜力。

基于ANSYS的真空热处理炉的温度场分析

利用ANSYS Workbench软件分析了管式真空热处理炉炉膛内部温度场分布,通过模拟隔热层放置位置/厚度、工件盒厚度/材质、筛网厚度/材质对炉膛内部均温区范围及其平均温度的影响,获得了不同热处理炉隔热层、工件盒与筛网的设计参数;通过优选设计参数,可使均温区长度从240 mm提升至320 mm,提升了33.33%,平均温度从958.25℃提升至962.94℃。最后采用优化后的热处理炉结构参数对负载Nd2Fe14B试样的温度场进行了仿真。结果表明,Nd2Fe14B永磁体的均温区范围及平均温度得到了明显提升,磁体平均温度从959.07℃提高到963.06℃,且磁体的温度起伏明显趋于平稳,从±1.06℃优化至±0.21℃。

飞行保护头盔用TC4护目镜支架的热处理研究

为解决头盔用TC4合金护目镜支架强度低的问题,对其进行真空热处理,用金相显微镜、扫描电子显微镜等研究真空热处理工艺对护目镜支架显微组织及性能的影响。结果表明:在真空度为1×10^(-3)Pa下,1000℃保温20 min后淬火,合金发生相变,平均尺寸为2.6μm的等轴α相转变为宽度约为870 nm的细小片层α相,并弥散分布于β基体中,β晶粒平均尺寸约为260μm。相对原始组织,经真空热处理后,合金屈服强度和抗弯强度分别从1596、1942 MPa提高到1806、2170 MPa,分别提升13%、12%,这是因为纳米片层α相弥散分布的强化效应,显著提升了合金的强度等力学性能。

退火温度对ITO/Cu/AZO透明导电薄膜结构及性能的影响

采用射频与直流磁控交替溅射法在石英玻璃载玻片上制备了氧化铟锡(ITO)/Cu/Al掺杂ZnO(AZO)(45 nm/10 nm/45 nm)组合结构的透明导电薄膜,并在不同退火温度下对薄膜进行真空热处理。利用X射线衍射仪(XRD)、紫外-可见分光光度计、四探针电阻测试仪等表征手段,系统地研究了退火温度对ITO/Cu/AZO复合薄膜晶体结构和光电性能的影响。结果显示,经过不同温度的真空退火处理,薄膜的晶体结构和导电性能得到显著改善和提高,薄膜可见光平均透过率随着退火温度的升高先增加后降低。对比发现,在气压5×10^(-3)Pa、温度150℃下退火制备的ITO/Cu/AZO结构薄膜表现出最佳的综合性能,薄膜具有较强的(222)和(440)晶面衍射峰,在400~800 nm光波范围平均透过率约为80.5%,电导率约为1.76×10^(3) S/cm,综合品质因数达到约2.12×10^(-3)/Ω。

冷喷涂CoNiCrAlY涂层制备工艺及组织性能研究

CoNiCrAlY合金可用于航空发动机热端部件的高温涂层,其使用性能因制备工艺的不同而呈现出差异。传统热喷涂技术在制备涂层过程中会引入高温热源,可导致材料发生相变,且产生一定的热应力。为消除热应力,需在喷涂至一定厚度后对涂层进行热处理,这导致了热喷涂技术制备大厚度涂层时喷涂效率的降低和成本的增加。围绕航空发动机涡轮外环高温封严涂层新一代制备技术需求,采用高压冷喷涂技术,以氮气为载气,国产CoNiCrAlY粉末为原料,开展了低成本冷喷涂CoNiCrAlY涂层的制备工艺及组织性能研究。实验采用φ100.50 mm 304不锈钢管基体,在69°喷涂角度、5 MPa喷涂压力下,分别在800、850和900℃喷涂温度条件下沉积制备了CoNiCrAlY涂层。测量了粉末在不同喷涂温度下的沉积效率,表征了涂层的微观结构、显微硬度和摩擦磨损性能,以1050℃保温5 h随炉冷却方式对涂层进行了真空热处理,研究了热处理后涂层的组织与性能变化。结果显示,涂层孔隙率随喷涂温度的升高而降低(2.07%、0.81%和0.44%),粉末颗粒的沉积效率随喷涂温度的升高而提高(29.7%、32.5%和36.1%),喷涂态涂层的显微硬度与喷涂温度之间无线性关系(585.32、526.21和563.52 HV_(0.3))。经真空热处理后,冷喷涂CoNiCrAlY涂层孔隙率均显著降低,均下降至0.4%左右。显微硬度显著下降,保持在360 HV_(0.3)左右。摩擦磨损测试结果表明,较低喷涂温度制备的CoNiCrAlY涂层,经真空热处理后具有更低的磨损率。