电热爆炸法原位合成Fe-Al系金属间化合物涂层的研究

利用电热爆炸喷涂装置将纯铝喷涂到Q235钢基体上原位合成FeAl和Fe3Al金属间化合物涂层,通过X射线衍射仪、扫描电镜、能谱仪和显微硬度计对涂层的物相进行了分析.结果表明,采用电热爆炸法在合适的喷涂距离下可合成具有亚微米晶的Fe3Al金属间化合物涂层,该涂层的硬度达630 HV0.05.涂层与Q235钢基体实现了冶金结合.     

WC/FeAl金属间化合物基金属陶瓷涂层的冷喷涂制备

采用WC/Fe/Al混合粉末,通过机械合金化制备40v0l％ WC/Fe(Al)固溶体复合粉末,利用冷喷涂沉积涂层并结合热处理原位反应制备了WC/FeAl金属间化合物基金属陶瓷涂层.研究了球磨时间对复合粉末相结构、晶粒尺寸及组织结构的影响,并分析了冷喷涂WC/FeAl金属间化合物基金属陶瓷涂层的组织和显微硬度.结果表明,机械合金化可获得WC陶瓷颗粒呈微/纳米多尺度分布的WC/Fe(Al)金属陶瓷复合粉末,球磨36 h的复合粉末基体相平均晶粒尺寸约为90 nm,冷喷复合涂层组织致密、多尺度WC颗粒在基体中均匀弥散分布,涂层显微硬度约为1060 HV0.3,涂层在650℃热处理后发生Fe(Al)固溶体向FeAl金属间化合物的原位转变,制备出了WC/FeAl金属间化合物基金属陶瓷涂层.     

高速电弧喷涂铁铝涂层的组织和性能

采用粉芯丝材和高速电弧喷涂技术（HVAS）原位合成了铁铝金属化合物涂层，并研究了涂层的显微组织和性能。结果表明，铁铝涂层的成分（原子分数，%）为Fe-20.0Al-14.1O，主要相是Fe3Al、FeAl和a-Fe相，还有少量Al2O3。涂层中的Fe3Al和FeAl具有较高的有序度。涂层具有相对较高的结合强度和显微硬度，以及较低的密度和孔隙率。     

高速火焰喷涂Fe-Al／SiC复合涂层组织与性能

利用高速火焰喷涂技术制备出Fe-Al/SiC复合涂层,采用扫描电镜、透射电镜、金相显微镜、能谱和X射线衍射仪对涂层的组织成分和相组成进行观察分析.研究表明,Fe-Al/SiC复合涂层基体为Fe-Al相(Fe3Al、FeAl),SiC硬质相分布于涂层之中,过渡相FeSi的存在使SiC硬质相与基体结合良好.整个涂层组织致密,呈现典型层状特征,涂层与基体结合良好,具有较高的结合强度和显微硬度,孔隙率低,抗热震性能优异.     

激光熔覆MoSi2粉末涂层的组织结构和性能

用XRD、SEM、EDAX和显微硬度仪研究了 4 5钢基体激光熔覆MoSi2 粉末涂层的组织结构和硬度。结果表明 ,由于基体的稀释作用 ,涂层的相组成为FeMoSi、Fe2 Si和少量的Mo5Si3 。涂层组织呈现典型的细小枝晶组织特征 ,枝晶为FeMoSi领先相 ,枝晶间为FeMoSi和Fe2 Si两相共晶 ,组织中无孔隙和裂纹等缺陷。Mo、Si、Fe线扫描成分分析表明 ,这些元素都分布在涂层 基体界面处 ,且缓慢过渡 ,基体与涂层发生互扩散 ,为冶金结合。涂层硬度可达 84 5HV0 5 ,基体硬度为 180HV0 5 ,涂层硬度比基体高 3 7倍。从涂层到基体硬度逐渐降低 ,过渡区比较缓和。     

高速电弧喷涂Fe-Al/Cr3C2复合涂层的组织与性能

采用Fe-Al/Cr3C2粉芯丝材和高速电弧喷涂技术(HVAS)原位合成了铁铝金属间化合物涂层,并研究了涂层的显微组织与性能.结果表明,高速电弧喷涂Fe-Al/Cr3C2涂层中生成了多种物相,主要是Fe3Al和FeAl相,同时还包括Fe3C硬质点相及FeO*Al2O3和Cr2O3氧化物相等.涂层具有很高的热震结合强度及相对基体较高的显微硬度,密度和孔隙率较低.     

火焰喷涂热障陶瓷梯度涂层的制备工艺及性能

在优化热障梯度涂层和过渡层的成分设计及氧乙炔火焰法制备工艺的基础上，获得了组织致密，有良好冶金结合的Al2O3／Fe热障梯度涂层。结果表明，涂层中的Al2O3分布基本均匀，且在整个涂层中，从钢基体到涂层表面的化学成分呈梯度分布，涂层与钢基体及各涂层之间存在明显的冶金结合；所获得的Al2O3热障梯度涂层与普通纯Al2O3热障涂层和带底层（Ni）和过渡层（Cu）的热障涂层相比，与基体间的结合力显著提高，弯曲强度、耐热冲击性能大为增强，涂层热障效果随涂层的数量和Al2O3含量的增加也获得明显提高。     

激光熔覆原位合成α-Fe(Al)/Fe3Al涂层的研究

通过寻求工艺参数与Fe-28％(at)Al粉末的最佳匹配，利用激光熔覆和复合材料原位合成技术，制备了熔覆质量好的α—Fe(Al)／Fe，Al涂层。该熔覆层为α—Fe(A1)固溶体胞状组织基体上分布着黑色DO3结构Fe3Al质点，多数质点分布在晶界上，颗粒尺寸为(100～300)nm。EDAX线扫描结果表明，Al、Fe在整个涂层中分布比较均匀，无宏观偏析；Al、Fe成分在近界面及界面处缓慢过渡，涂层和基体发生互扩散，为冶金结合。熔覆层的显微硬度为639HV0．2，比基体高2倍，多道搭接处理对熔覆层的硬度影响不大。     

低碳钢喷铝扩散法渗铝的组织分析

研究了20钢表面火焰喷涂铝后扩散处理工艺.通过SEM和EPMA分析了喷铝扩散渗层的组织结构及成分变化情况,并进行了显微硬度测试.结果表明：喷铝扩散涂层由表及里依次为ζ相（FeAl2）,β2相（FeAl）,β1相（Fe3Al）相及α相,其中β2相为主要相,各相间平衡过渡.渗层具有较高的硬度.     

反应等离子喷涂制备FeAl2O4-Al2O3-Fe复合涂层的研究

以铝粉和氧化铁粉为原料,制备出适于等离子喷涂的复合团聚粉体;并采用反应等离子喷涂技术制备出FeAl2O4-Al2O3-Fe复合涂层,用SEM和XRD分析了复合涂层的组织结构.结果表明反应等离子喷涂得到了以层状基体相FeAl2O4与硬质相Al2O3为骨架,球状Fe相弥散分布于基体上的复合涂层.     

Interface microstructure and formation mechanism of diffusion-bonded joints of TiAl to steel 40Cr

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H13钢表面电火花沉积钼涂层的摩擦磨损特性研究

在H13钢表面电火花沉积钼合金涂层,研究了其组织结构及摩擦磨损特性。结果表明,钼合金涂层由白亮层、扩散层和热影响区组成;钼元素与基体元素相互扩散形成冶金结合;合金层的显微硬度(约为1482HK0.025)较H13钢(280HK0.025)提高5倍左右;电火花沉积Mo合金层后摩擦系数明显降低,磨损质量损失仅为基材的1/7,抗磨性能显著提高。     

TiAlN涂层的热残余应力分析

采用有限元方法分析氮铝钛涂层的残余热应力,研究不同的基体及过渡层对残余热应力分布的影响。结果表明：当基体为硬质合金时,涂层内以拉应力为主,而基体为不锈钢时,涂层内以压应力为主;增加过渡层可以使涂层内的残余应力减少40%以上;硬质合金基体中涂层的拉应力随基体钴含量和涂层厚度的增加而减少;无过渡层时,不锈钢基体存在明显的塑性约束区,有过渡层时,随着界面应力的减少,塑性约束区明显减小或消失。因此,通过不同的涂层和基体搭配可以改善应力场,同时增加过渡层可以缓和界面应力和增强界面结合力。     

激光熔覆MoB/CoCr金属陶瓷涂层的微观组织

采用5 kW CO2激光器在45钢表面激光熔覆制备MoB/CoCr金属陶瓷涂层,对涂层的微观组织、成分分布和显微硬度进行研究。结果表明,MoB/CoCr金属陶瓷涂层组织致密,与基体呈冶金结合。激光熔覆的熔覆区中的主要元素是Mo、Cr和Co,合金化区由于元素互扩散,Fe元素含量明显增加。激光熔覆后MoB/CoCr金属陶瓷涂层的硬度远远大于基体的硬度,起到了表面强化的作用。     

温度对热浸铝及后续扩散中镀层的影响

采用热浸镀铝法在不锈钢表面制备铁铝镀层并分析了镀层的组织结构及其影响因素。结果表明：热浸镀纯铝后,镀层由表面铝层和合金层组成,层间结合紧密,镀层较厚。随浸铝温度的升高,外层铝层减薄,而内层合金层明显增厚,镀层总厚度并没有太大差异,在800℃时镀层质量最为优异。在热扩散实验时,900℃时形成的扩散层质量最佳,为韧性相FeAl固溶体和a-Fe（Al）固溶体,镀层中没有孔洞及裂纹生成,为理想的过渡层材料。     

Cu的添加对X80钢热浸法渗铝层组织的影响

通过在热浸镀铝熔池中添加Cu元素,改善X80钢热浸法渗铝层的组织。在不同的温度下进行扩散退火试验,利用扫描电镜和X射线衍射仪研究退火温度和铜元素对渗层组织的作用机理。采用Smile View软件对渗层厚度进行测量。结果表明,在热浸法渗铝时,Cu的添加可以使合金层/X80钢基体界面间的舌齿状形态缩小,使得界面间反应更均匀。当Cu的添加量为1%(质量分数)时,脆性的Fe₂Al₅合金层的厚度最小。随着扩散退火温度的升高,Cu添加量为1%的试样渗层的界面均匀性增加;扩散退火温度≥600℃时,渗层中开始出现极薄的FeAl相层;扩散退火温度≥650℃时,自由层消失,渗层中出现均匀的FeAl层且渗层外侧出现孔洞;扩散退火温度为700℃时,FeAl层中部出现孔洞带,且渗层外侧出现大孔洞。在热浸镀铝熔池中加入1%Cu元素可以使扩散退火过程中Al原子和Fe原子间的迁移速率差值减小,进而降低Al原子和Fe原子间的浓度梯度。原子间浓度梯度的降低,使得界面间反应更均匀,从而避免渗层中孔洞的出现。     

Microstructure Evolution of Hot-Dip Al-10% Si Coating During the Austenitization of 22MnB5 Hot Stamping SteelEI北大核心CSCD

Hot stamping is an alternative technology to produce ultra-high strength steel (UHSS) with a tensile strength above 1 GPa for automotive bodies. At present, the hot-dip Al-10% Si (mass fraction) coating is used as a shield coating for the hot stamping steels, which protects the steels from surface oxidation and decarburization, and enhances their corrosion resistance. However, the microstructure evolution and compounds of hot-dip Al-10% Si coating during austenitization of 22MnB5 hot stamping steel are not clear yet. In this work, the thermo-mechanically induced microstructure evolution of hot-dip Al-10% Si coating is observed using SEM after austenitization of 22MnB5 hot stamping steel at 900 degrees C for different times, and the elemental depth profiles are analyzed in hot-dip Al-10% Si coating by EDS and GD-OES. The results show that before austenitization, the hot-dip Al-10% Si coating consisted of an aluminum matrix, pure silicon, and the intermetallic compound Fe2SiAl7, which was formed by eutectic reaction, there was a thin layer, which was composed of Fe2Al5 and FeAl3 between the intermetallic compound Fe2SiAl7 and the steel substrate. When 22MnB5 hot stamping steel was austenitized at 900 degrees C, the ternary eutectic phase Al+ Si+ tau(6) was transformed into an Al-Fe-Si ternary intermetallic compound or Fe-Al binary intermetallic compound gradually in the hot-dip Al-10% Si coating. When the austenitizing time was 2 min, the Al-10% Si coating was composed of the intermetallic compound Fe2SiAl7, Fe2Al5 and FeAl2 phases; when the austenitizing time was 5 min, the Al-10% Si coating was composed of FeAl2, Fe2SiAl2 and Fe5SiAl4 phases; when the austenitizing time was 8 min, the Al-10% Si coating was composed of FeAl2 and Fe5SiAl4 phases. Because the diffusion rate of Al atoms was much larger than that of Fe atoms in the diffusion layer of intermetallic compound Fe2SiAl2 and coating/steel substrate, the amount of Al atoms which diffused and reacted from the coating to the grain boundaries or grain of steel substrate was much larger than that of the Fe atoms which diffused from the steel substrate to the Al10% Si coating, also the number of vacancies which diffused from the steel substrate to the Al-10% Si coating was much larger than the other way round. Due to this imbalance, the Kirkendall void was formed in the interface between the diffusion reaction layer and the Al-10% Si the coating. The hot-dip Al-10% Si coating can be used as the protective layer, since it has a stable Al2O3 film formed on its surface, and its thermal oxidation was very limited, during the 22MnB5 hot stamping steel austenitizing. But the protective performances of Al-10% Si coating could be poor, because the high temperature ductility of brittle intermetallic compound was low, which induced a lot of micro cracks that were perpendicular to the interface of coating/steel substrate, and penetrated the whole coating during the diffusion process of hot-dip Al-10% Si coating.     

热浸铝钢等离子体电解氧化陶瓷层的微观力学特性

采用纳米压入方法表征了热浸镀铝钢表面由Al2O3层、Al层和FeAl层组成的复合涂层的纳米硬度、弹性模量及断裂韧性等微观力学性能,采用扫描电镜(SEM)观察了纳米压痕形貌,并分析了孔洞对陶瓷层的纳米压入行为和压痕裂纹扩展的影响.结果表明:等离子体电解氧化(PEO)陶瓷层中包含许多微米和亚微米尺度的细小孔洞,陶瓷层弹性模量约为226.4 Gpa,纳米硬度约为19.6 Gpa.当纳米压入深度为250 nm时,所测得陶瓷层的力学参数分散性较大.与FeAl层比较,PEO陶瓷层具有较高的裂纹扩展阻力. FeAl层纳米压痕顶端产生了沿直线扩展的径向裂纹;而陶瓷层纳米压痕中除径向裂纹外出现了侧边裂纹.     

Formation and structure of composite coating of HDA and micro-plasma oxidation on A3 steel

Composite coatings were obtained on A3 steel by hot dipping aluminum(HDA) at 720 ℃ for 6 min and micro-plasma oxidation(MPO) in alkali electrolyte. The surface morphology, element distribution and interface structure of composite coatings were studied by means of XRD, SEM and EDS. The results show that the composite coatings obtained through HDA/MPO on A3 steel consist of four layers. From the surface to the substrate, the layer is loose Al2O3 ceramic, compact Al2O3 ceramic, Al and FeAl intermetallic compound layer in turn. The adhesions among all the layers are strengthened because the ceramic layer formed at the Al surface originally, FeAl intermetallic compound layer and substrate are combined in metallurgical form through mutual diffusion during HDA process.Initial experiment results disclose that the anti-corrosion performance and wear resistance of composite coating are obviously improved through HDA/MPO treatment.     

球铁浸镀微弧氧化陶瓷层的制备与组织分析

通过热浸镀铝及微弧氧化的方法在球墨铸铁表面上获得了陶瓷层,并对该涂层进行了XRD、SEM分析.研究结果表明:浸镀温度越高,镀层越厚,直到达到一峰值;浸镀时间越长,镀层越厚.球墨铸铁浸镀微弧氧化获得的涂层由涂层表面至基体依次为陶瓷层、纯铝层、扩散层、基体.陶瓷层主要为Al2O3相,扩散层由FeAl3、Fe2Al5相组成.