Cr_3C_2-NiCr涂层的工程化应用研究

从工程化应用的角度出发,比较了超音速火焰喷涂工艺(HVOF)和等离子喷涂工艺制备的Cr3C2-NiCr涂层性能差别,发现HVOF工艺制备的Cr3C2-NiCr涂层质量明显优于等离子喷工艺,从而采用HVOF工艺作为Cr3C2-NiCr涂层优选的喷涂方法。HVOF工艺制备的Cr3C2-NiCr陶瓷涂层具有硬度高(HV300>9800MPa)、孔隙率低(<0.9%)、与基体结合强度高(>70MPa)等特点,满足柴油机关键部件缸套涂层的使用要求。     

镁合金表面冷喷涂纳米WC-17Co涂层及其性能

采用冷喷涂和超音速火焰喷涂(HVOF)在AZ80镁合金表面制备了纳米WC-17Co涂层。利用SEM分析了原始粉末形貌、喷涂粒子沉积行为及涂层显微结构,并采用球盘式摩擦磨损实验机考察了涂层的摩擦磨损性能。结果表明:采用冷喷涂工艺可在AZ80镁合金基体上制备出高质量的WC-17Co涂层,涂层的显微硬度为(1 380±82)HV,磨损率为9.1×10-7 mm3/Nm,其耐磨性较HVOF制备的WC-17Co涂层提高了1倍,较镁合金基材提高了3个数量级。研究表明,冷喷涂WC-17Co涂层在不对镁合金基体产生热影响的情况下,可以显著提高镁合金的表面性能,是一种新型镁合金表面强化工艺。     

对用于涡轮机械上的优化涂层的HVOF工艺条件的评论

在磨损和腐蚀非常严重的情况下，由超音速火焰喷涂(HVOF)工艺产生的涂层成功地延长了涡轮机械零件的使用寿命。在喷涂过程中，粉末粒子达到极高的冲击速度，从而形成具有高耐磨抗腐蚀能力的坚固耐用的涂层。本文介绍有关HVOF工艺、涂层以及HVOF在涡轮机械上的典型应用。     

热喷涂钴基合金涂层的耐气蚀性能

评价了用于耐蚀涂层的热喷涂钴基合金涂层的抗气蚀性能。钴基合金涂层分别用低压等离子喷涂(LPS)和高速氧燃料气火焰喷涂(HVOF)喷涂在AISI304不锈钢基体上,其中每种涂覆试样的一半试样进行了1073K×1h的后续加热处理。在本试验中,为了进行评价而测量了试样的重量损失。由气蚀试验得到如下结果:1)用LPS喷涂的两种涂层(喷后加热处理的和喷涂态的)比HVOF涂层具有更优越的抗气蚀性能;2)对于LPS喷涂层,喷后加热处理过的涂层与喷涂态的涂层具有相同的重量损失;3)对HVOF涂层喷后热处理非常有效地改善了抗气蚀性能。     

超音速火焰喷涂MCrAlY粘结层对热障涂层热震性能的影响

分别采用超音速火焰喷涂技术(HVOF)和等离子喷涂技术(APS)在高温合金GH99上制备MCrAIY粘结层(BC),对比研究了HVOF和APS喷涂BC对热障涂层(TBC)热震性能的影响.结果表明:APS喷涂BC界面不平整,起伏较大,而HVOF喷涂BC界面较为平整.经200次热循环后,APS喷涂TBC部分陶瓷层(TC)出现剥落,而HVOF喷涂TBC仅出现细小的微裂纹,生成的热生长氧化物(TGO)比较厚.APS喷涂TBC经过350次热循环后,涂层出现大面积剥离现象.而HVOF热障涂层直到热震430次后,才出现涂层剥落现象.拉曼光谱(RFS)残余应力分析表明,HVOF热障涂层残余应力随热循环次数的增加而增大,热震350次后APS热障涂层残余应力为650MPa,而HVOF热障涂层热震400次后其应力值仅为571 MPa.可知,HVOF显著地提高了TBC的热震性能.     

喷涂角度对HVOF WC-Co-Cr涂层分布的影响（英文）

在喷涂复杂形状部件时,高速氧燃气(HVOF)喷涂焰流和基体表面几乎不可能固定一个角度。研究喷涂角度对涂层性质的影响是必要的,并研究了凹面曲率半径对沉积率的影响。实验使用团簇烧结的WC-10Co-4Cr粉末(粒度15~45μm)。实验时喷涂参数不变,喷涂半径为10,15,25 mm的凹面。结果表明,喷涂角度严重影响涂层沉积率。喷涂角度减小导致沉积率减少。当喷涂角度小于30°,涂层性质显著降低。涂层沉积分布和不同凹面半径的关系被推导。     

对用于涡轮机械上的优化涂层的HVOF工艺条件的评论

在磨损和腐蚀非常严重的情况下，由超音速火焰喷涂（HVOF）工艺产生的涂层成功地延长了涡轮机械零件的使用寿命。在喷涂过程中，粉末粒子达到极高的冲击速度，从而形成具有高耐磨抗腐蚀能力的坚固耐用的涂层。本文介绍有关HVOF工艺、涂层以及HVOF在涡轮机械上的典型应用。     

粉末尺寸和喷涂工艺对超音速火焰喷涂WC-10Co-4Cr涂层冲蚀磨损性能的影响

对2种不同粒度的WC-10Co-4Cr粉末,在不同超音速火焰(HVOF)喷涂工艺参数条件下制备涂层。采用正交回归试验方法研究了喷涂工艺对HVOF WC-10Co-4Cr涂层耐冲蚀性能的影响,并探讨了粉末尺寸对涂层耐冲蚀性能的影响。采用扫描电镜观察涂层的冲蚀表面形貌,以分析涂层的冲蚀机理。结果表明:粉末尺寸、丙烷气体流量、氧气流量和喷涂距离对HVOF WC-10Co-4Cr涂层耐冲蚀性能有较大影响。在正交试验的结果基础上,建立了冲蚀磨损率与喷涂工艺参数之间的二次回归方程。在低角度冲蚀时涂层的冲蚀机理主要是犁削磨损,而大角度冲蚀时主要是喷涂粒子的层间剥落。     

HVOF喷涂成形纳米晶FeAl厚涂层的结构和热稳定性

采用超音速火焰喷涂(HVOF)成形工艺喷涂球磨粉末，成功制备了纳米晶FeAl厚涂层(5mm)．分别利用SEM、图像分析、TEM以及Vickers硬度表征了该涂层的微观结构，并与用相同的喷涂参数和原料粉末制备的纳米晶薄涂层(300μm)进行了比较，研究了不同的喷涂条件对涂层的结构及其硬度的影响．同时，探讨了厚涂层的热稳定性．结果表明，由于涂层中较好地保留了未融粒子中的纳米晶，从而在600℃仍能保持原有的高硬度．     

三种超音速热喷涂工艺制备WC-12Co涂层的组织结构分析

用新研制的超音速等离子喷涂(S—APS)和2种进口超音速火焰喷涂(HVOF)设备制备了WC—12Co涂层，分析了3种喷涂工艺对涂层的表面和断面显微形貌、组织结构、孔隙率和氧化、脱碳，以及涂层的显微硬度、结合强度的影响。结果表明，在所试验的条件下，超音速等离子喷涂WC—12Co涂层显示出最致密的组织结构和最高的显微硬度。     

Improving corrosion properties of high-velocity oxy-fuel sprayed inconel 625 by using a high-power continuous wave neodymium-doped yttrium aluminum garnet laser

Thermal spray processes are widely used to protect materials and components against wear, corrosion and oxidation. Despite the use of the latest developments of thermal spraying, such as high-velocity oxy-fuel (HVOF) and plasma spraying, these coatings may in certain service conditions show inadequate performance,e.g., due to insufficient bond strength and/or mechanical properties and corrosion resistance inferior to those of corresponding bulk materials. The main cause for a low bond strength in thermalsprayed coatings is the low process temperature, which results only in mechanical bonding. Mechanical and corrosion properties typically inferior to wrought materials are caused by the chemical and structural inhomogeneity of the thermal-sprayed coating material. To overcome the drawbacks of sprayed structures and to markedly improve the coating properties, laser remelting of sprayed coatings was studied in the present work. The coating material was nickel-based superalloy Inconel 625, which contains chromium and molybdenum as the main alloying agents. The coating was prepared by HVOF spraying onto mild steel substrates. High-power continuous wave Nd:YAG laser equipped with large beam optics was used to remelt the HVOF sprayed coating using different levels of power and scanning speed. The coatings as-sprayed and after laser remelting were characterized by optical microscopy and scanning electron microscopy (SEM). Laser remelting resulted in homogenization of the sprayed structure. This strongly improved the performance of the laser-remelted coatings in adhesion, wet corrosion, and high-temperature oxidation testing. The properties of the laser-remelted coatings were compared directly with the properties of as-sprayed HVOF coatings and with plasma-transferred arc (PTA) overlay coatings and wrought Inconel 625 alloy.     

喷涂距离对超音速火焰喷涂 CoCrAlYTa 涂层组织性能的影响

采用超音速火焰喷涂技术制备CoCrAlYTa涂层,研究了喷涂距离对涂层相组成、孔隙率以及硬度、弯曲强度、高温抗氧化性能的影响。结果表明:喷涂距离在200～300 mm范围内时,随着喷涂距离的减小,涂层的致密度增加,孔隙率下降,显微硬度和弯曲结合强度增加,但相组成基本不变,主要由CoAl,AlCo2Ta和CoTa3相组成;涂层致密度越高,在高温氧化过程中,表面越易尽早形成连续氧化膜并促进涂层中Al元素的选择氧化,因此随着喷涂距离的减小,涂层的高温抗氧化性能逐渐增强。     

Microstructural Evolution of SAPS/HVOF CoNiCrAlY Alloy Coating During Thermal Cycling Test

In this paper, CoNiCrAlY alloy coatings were deposited by high-efficiency supersonic atmospheric plasma spraying (SAPS) and high-velocity oxygen fuel (HVOF) spraying. The microstructural evolution of coatings during thermal cycling test was investigated. The results suggested that the as-sprayed SAPS coating consisted of lamellar structures and unmelted particles. However, the as-sprayed HVOF coating primarily consisted of the unmelted particles. The β-NiAl phase mainly existed in the unmelted particles, and its content increased with the increase of unmelted particles. The thermal cycling life of SAPS coating was 258 cycles, about 117 % higher than that of HVOF coating. During thermal cycling, significant internal oxidation and large cracks formed in the HVOF coating, which was one of the reasons that led to the spallation of HVOF coating.     

高速火焰与等离子喷涂WC／Co涂层的性能比较

分析比较了超音速喷涂与等离子体喷涂的ＷＣ／Ｃｏ涂层的形貌,显微组织结构,孔隙率,硬度及其耐磨性,结果表明超音速火焰喷涂的ＷＣ／Ｃｏ涂层具有与粉末相近的相结构,也说ＷＣ颗粒在超音速火焰喷涂过程中,只有极少部分被分解和氧化,同时涂层具有很高的致密度,硬度和良好的耐磨性,涂层与基体的结合情况也得到很大的改善。     

Corrosion behavior of HVOF-sprayed and Nd-YAG laser-remelted high-chromium,nickel-chromium coatings

Thermal spray processes are widely used to deposit high-chromium, nickel-chromium coatings to improve high temperature oxidation and corrosion behavior. However, despite the efforts made to improve the present spraying techniques, such as high-velocity oxyfuel (HVOF) and plasma spraying, these coatings may still exhibit certain defects, such as unmelted particles, oxide layers at splat boundaries, porosity, and cracks, which are detrimental to corrosion performance in severe operating conditions. Because of the process temperature, only mechanical bonding is obtained between the coating and substrate. Laser remelting of the sprayed coatings was studied in order to overcome the drawbacks of sprayed structures and to markedly improve the coating properties. The coating material was high-chromium, nickel-chromium alloy, which contains small amounts of molybdenum and boron (53.3% Cr, 42.5% Ni, 2.5% Mo, 0.5% B). The coatings were prepared by HVOF spraying onto mild steel substrates. A high-power, fiber-coupled, continuous-wave Nd:YAG laser equipped with large beam optics was used to remelt the HVOF-sprayed coating using different levels of scanning speed and beam width (10 or 20 mm). Coating that was remelted with the highest traverse speed suffered from cracking because of the rapid solidification inherent to laser processing. However, after the appropriate laser parameters were chosen, nonporous, crack-free coatings with minimal dilution between coating and substrate were produced. Laser remelting resulted in the formation of a dense oxide layer on top of the coatings and full homogenization of the sprayed structure. The coatings as sprayed and after laser remelting were characterized by optical and electron microscopy (OM, SEM, respectively). Dilution between coating and substrate was studied with energy dispersive spectrometry (EDS). The properties of the laser-remelted coatings were directly compared with properties of as-sprayed HVOF coatings.     

Coating of High-Alloyed, Ledeburitic Cold Work Tool Steel Applied by HVOF Spraying

This study demonstrates the processing of a cold work tool steel (X220CrVMo13-4) coating using HVOF spraying. The coating formation was analyzed based on microstructure, phase, hardness, porosity, oxidation, and adhesion characteristics. An online diagnostic tool was utilized to find out the in-flight characteristics of powder such as temperature and velocity during the coating process to identify the influencing parameters to achieve dense cold work tool steel coatings with low oxidation. The influence of powder size, process parameters, and in-flight characteristics on the formation of cold work tool steel coatings was demonstrated. The results indicated that thick and dense cold work tool steel coatings with low oxidation can be obtained by the selection of appropriate powder size and process parameters.     

Development of cold work tool steel based-MMC coating using HVOF spraying and its HIP densification behaviour

The aim of the present study is to develop a Fe-based metal matrix composite (MMC) coating using high velocity oxy-fuel spraying (HVOF) process. A ledeburitic high alloyed cold work tool steel (X220CrVMo13-4) and NbC with an average size of 2 µm at different volume fractions have been considered as metal matrix and hard particles respectively. MMC coatings were deposited on austenitic stainless substrates and the coatings were subsequently densified by hot isostatic pressing (HIP) with and without encapsulation. Microstructural analysis of the as-sprayed and HIPed coatings were characterized by SEM and XRD methods. Results showed that the feedstock preparation involving fine NbC was an influencing factor on the coating deposition. A relatively homogeneous dispersion of fine NbC up to 30 vol.% in cold work tool steel matrix was possible using optimized HVOF spraying. Besides, HVOF spraying and its subsequent HIP treatment induced significant microstructural and phase changes in the MMC coatings. The study showed the potential of HVOF spraying for the development of steel based MMC coatings and its subsequent densification can be achieved by HIP process with and without encapsulation.     

粉末结构对超音速火焰喷涂WC系金属陶瓷涂层结合强度的影响

采用４种典型的ＷＣ系硬质合金粉末与Ｗ－Ｎｉ复合粉末,研究了粉末结构、粘结相的成分与含量,以及超音速火焰喷涂（ＨＶＯＦ）条件对涂层结合强度的影响。结果表明：对于具有高熔点的ＷＣ及Ｗ颗粒构成的复合粉末,ＨＶＯＦ涂层的结合强度大于结胶的强度,几乎不受粉末结构和粘结相成分的影响。试验表明：喷涂料子具备液固两个相结构是ＨＶＯＦ涂层获得高结合强度的必要条件,而ＷＣ与Ｗ的高密度是保证ＨＶＯＦ涂层高结合强度的充分     

FeAl and Mo–Si–B intermetallic coatings prepared by thermal spraying

FeAl and Mo–Si–B intermetallic coatings for elevated temperature environmental resistance were prepared using high-velocity oxy-fuel (HVOF) and air plasma spray (APS) techniques. For both coating types, the effect of coating parameters (spray particle velocity and temperature) on the microstructure and physical properties of the coatings was assessed. Fe–24Al (wt%) coatings were prepared using HVOF thermal spraying at spray particle velocities varying from 540 to 700 m/s. Mo–13.4Si–2.6B coatings were prepared using APS at particle velocities of 180 and 350 m/s. Residual stresses in the HVOF FeAl coatings were compressive, while stresses in the APS Mo–Si–B coatings were tensile. In both cases, residual stresses became more compressive with increasing spray particle velocity due to increased peening imparted by the spray particles. The hardness and elastic moduli of FeAl coatings also increased with increasing particle velocity. For Mo–Si–B coatings, plasma spraying at 180 m/s resulted in significant oxidation of the spray particles and conversion of the T1 phase into amorphous silica and -Mo. The T1 phase was retained after spraying at 350 m/s.