激光重熔对NiCrBSi等离子喷涂层显微结构和性能的影响

1Crl8Ni9Ti不锈钢表面的NiCrBSi等离子喷涂层存在孔洞及与基体结合差等缺陷,为此进行了激光重熔处理.采用扫描电镜和显微硬度压痕仪分别对涂层的显微结构和力学性能进行了对比研究,采用SRV试验机评价了涂层激光重熔前后的滑动摩擦磨损性能,研究了激光重熔对NiCrBSi等离子喷涂层结构和性能的影响.结果表明:经过激...     

线圈扫描速度对感应熔覆Ni CrBSi涂层组织与性能的影响

以自熔性合金粉末Ni60为原料采用预置涂层结合高频感应熔覆技术在45钢基体表面制备了NiCrBSi涂层别用场发射扫描电镜、X射线衍射仪、显微硬度计和CETR摩擦磨损试验机等设备研究了感应线圈扫描速度对涂层微观组织、显微硬度和摩擦学性能的影响。结果表明,感应熔覆NiCrBSi涂层组织致密、内部无孔隙和裂纹等缺陷,涂层由γ-Ni/Fe基质相和弥散分布的Cr_7C_3、Cr_(23)C_6、CrB等硬质析出相构成。熔覆层最高硬度为980HV_(0.2),涂层内部残余应力呈压应力状态。随着线圈扫描速度的增大,涂层热输入量降低,熔池冷却凝固速度加快,一方面导致界面区域元素扩散减弱,涂层稀释率降低界面过渡区宽度减小;另一方面造成涂层晶粒和析出相尺寸细化,涂层显微硬度升高,涂层磨损形式由以粘着磨损为主向以磨粒磨损为主转变同时残余压应力增大,使得涂层耐磨性提高。     

喷涂工艺参数对NICrBSi涂层显微组织和性能的影响

采用微束等离子喷涂系统制备了NiCrBSi涂层。研究了电弧功率、喷涂距离和等离子气体流量对涂层显微组织和性能的影响。试验结果表明,NiCrBSi涂层的致密程度与显微硬度随电弧功率和气体流量的增加而增加。当喷涂距离超过40mm时,喷涂距离对涂层显微硬度没有显著影响。采用微束等离子喷涂工艺制备的NiCrBSi涂层显微硬度可达HV0．2700。     

合金成分对镍基合金激光熔覆涂层组织与性能的影响

为了研究激光熔覆镍基合金涂层显微组织与性能之间的关系,本文选用Ni25、Ni45、Ni60镍基自熔性合金粉末作为熔覆材料,在同一工艺参数下在45#钢基体上制得Ni25、Ni45、Ni60合金激光熔覆涂层。利用扫描电子显微镜(SEM)、能谱仪(EDS)、X射线衍射仪(XRD)、显微硬度计等方法对涂层的显微组织、物相组成、显微硬度等进行了研究。结果表明从Ni25到Ni60合金涂层,随着合金元素含量的提高,涂层微观组织逐渐由亚共晶转变为过共晶,γ-Ni奥氏体枝晶所占体积分数减少,尺寸细化,枝晶间的共晶组织和硬质相所占的体积分数增大,涂层和基体之间结合带的宽度越来越窄,熔覆层的显微硬度越来越高。Ni25、Ni45合金涂层的平均显微硬度分别为250HV和550HV左右,而Ni60合金涂层的平均硬度却高达750HV左右,为Ni25合金涂层的3倍。     

稀土含量对活性激光熔覆Fe-Cr-W-Ni-C涂层的组织和磨损性能的影响

采用活性激光熔覆技术,在45钢基体上制备添加质量分数为0.1%～0.4%稀土CeO2的Fe-Cr-W-Ni-C涂层,并研究其物相组成、显微组织、显微硬度、耐磨性能。结果表明:所得高熵合金涂层表面无气孔、裂纹等缺陷,高铝粉煤灰活性剂的加入增大了基体对涂层的稀释作用,使涂层与基体呈良好的冶金结合,高铝粉煤灰可有效增大熔池深宽比,有利于涂层更好地成形;合金涂层主要由α-Fe、γ-Fe组织以及碳化物构成。当RE添加质量分数为0.1%时晶粒细小而弥散,明显起到细晶强化的作用,提高了涂层的硬度和耐磨粒磨损性能,涂层硬度最高可达759 HV,磨损率最低为9.0%。     

镍基喷焊涂层与钛合金基体界面特征的研究

考察了三种工艺制备的镍基喷焊涂层与钛合金基体结合界面的组织形貌、涂层横切面上合金元素的扩散和显微硬度的变化,分析了它们的界面特征及影响因素.结果表明:镍基喷焊涂层与基体钛合金的结合是基于合金元素扩散的冶金结合,合金元素的扩散对涂层与基体能否形成冶金结合具有决定性的影响,钛合金表面的活化处理、涂层合金重熔时液态停留时间以及喷焊后进行时效处理是影响合金元素扩散的主要因素.     

冷喷涂Zn-Al合金涂层组织结构和力学性能研究

以Q235钢为基体制备高压冷喷涂Zn-Al合金涂层,研究了基体粗糙度对冷喷涂Zn-Al合金涂层组织结构、显微硬度和结合强度的影响。研究表明,冷喷涂Zn-Al合金涂层具有致密的组织结构,涂层孔隙率在0.5%以下,并且在喷涂过程中没有产生粉末相变和氧化,随着基体粗糙度增加,涂层-基体界面的机械咬合得到明显改善。基体粗糙度对涂层显微硬度的影响主要集中在涂层-基体界面附近,随着基体粗糙度增加,该界面附近涂层的显微硬度随之增加,而远离该界面的涂层显微硬度受基体粗糙度的影响不大。基体粗糙度对涂层结合强度有显著影响,当基体粗糙度由1.6增加到10.2μm时,涂层结合强度由7.5增加到46.4 MPa,拉伸断裂失效模式由粘着断裂转变为粘着断裂、粘聚断裂的复合失效模式。     

铝合金表面Ti-Al双丝超音速电弧喷涂涂层的组织与性能研究

利用SAS－1型超音速电弧喷涂设备和钛、铝丝在适当的工艺条件下，在LY12铝合金表面制成了钛铝合金复合涂层。并利用金相显微镜、X射线衍射仪、扫描电镜、X射线能谱仪、电子探针等，对涂层的成分、相结构、显微结构、孔隙率及其结合强度、显微硬度和耐磨性进行了研究。结果表明，利用超音速电弧喷涂设备，可以在铝基表面形成低孔隙率小于2.8%，结合强度为29MPa，显微硬度HV0.2为631和干滑动磨损体积仅为LY12基体1／7的TiAl合金涂层。显微组织观察发现，涂层与基体间有冶金结合的迹象，组织结构分析表明，涂层由TiN（TiO)，Al,Ti,TiAl,Ti3Al等相组成。涂层的磨损机制可能以化合物等硬质相的剥落引起的磨粒磨损和氧化磨损为主。     

316L不锈钢表面激光熔覆Stellite6合金组织及其耐液态铅铋腐蚀性能

为提高316L不锈钢耐高温液态铅铋的腐蚀能力,通过使用同轴送粉的激光熔覆方式,在316L不锈钢表面制备一层Stellite6合金涂层,将其放入400℃的高温液态铅铋中进行500 h高速流腐蚀试验,其中相对流速设置为2.56 m/s.分析涂层的微观组织、物相组成、元素分布、显微硬度值等的变化规律,以及该涂层耐液态铅铋的腐蚀性能.涂层组织由等轴晶、树枝晶、胞状晶及平面晶组成,搭接区晶粒沿不同方向长大;涂层主要有γ-Co、CoCx、(Cr,Fe)7 C3及M23 C6等物相;各组分元素在涂层表面均匀分布,Co、Cr与Fe等元素在基体316L与涂层之间发生明显扩散;Stellite6涂层的硬度平均值为基体材料316L的2.3倍,且最高达到556.8HV.在进行高温液态铅铋高速流腐蚀后,316L不锈钢表面生成了大面积且连续的氧化物,存在大量微型腐蚀坑,Stellite6涂层表面仅存在少量氧化物,未发现明显的腐蚀坑,较好地维持了原貌;Stellite6涂层表面粗糙度值为1.0μm,而316L经腐蚀后的表面粗糙度为2.4μm.Stellite6合金涂层能够有效地提高316L不锈钢基体在高温液态铅铋合金中的耐腐蚀性能.     

镍基合金粉末光束堆焊层的微观组织及强化机理

采用X射线衍射，SEM，EDAX及显微硬度和洛氏硬度等分析手段研究了含碳量为1．0％的NiCrBSi系自熔合金粉末光束堆焊层的微观组织及强化机理，结果表明，采用光束镍基合金粉末堆焊可在铁碳合金表面获得与基体冶金结合良好，无裂纹，轻度稀释的强化层，堆焊热输入对堆焊层稀释率及合金元素烧损的影响程度决定了堆焊层微观组织及物相组成，小热输入堆焊时，堆焊金属经度稀释（η=3.5%），其显微组织由少量初生的γ－Ni和大量的γ－Ni Bi3B Ni3Si三相共晶组成的亚共晶基底，以及在基底上分布着大量的Cr23C6,(Cr,Fe)7C3高硬度相组成，采用大热输入堆焊，堆焊金属稀释率达12％，堆焊层由大量的γ－（Fe,Ni0枝晶和少量γ－(Fe,Ni) M7C3共晶组成，在堆焊层中未发现一次碳化物的析出，在光束粉末堆焊层中大量高硬度M23C6,M7C3共晶组成，在堆焊层中未发现一次碳化物的析出，在光束粉末堆焊层中大量高硬度M23C6，M7C3型碳化物和Ni3B,Ni3Si共晶相的析出以及合金元素在γ相中的过饱和固溶是其是以强化的主要原因，与TIG堆焊相比，采用相近热输入所获得的光束粉末堆焊层的耐磨性能提高了3倍以上。     

Microstructure of Laser Remelted Ni-base Alloy Coating on Stainless Steel

A 5 kW CW CO2 gas laser was used to produce NiCrBSi superalloy coatings. Powders were preplaced by plasma-spraying. The microstructure and chemical composition of the coating have been studied by SEM, XRD and HREM. The results show the coating microstructure is fine dendrites, composed of γ matrix, γ' and boride (NiB) eutectic, the lattice parameter of the γ matrix is 0.3572 nm and there is a metallurgical bonding in interface.     

Mo含量对CoCrFeNiMo高熵合金组织及耐蚀性能的影响

高熵合金由于具有优异的机械性能及耐蚀性能在涂层工业领域备受关注。采用同步送粉激光熔覆技术在Q235钢表面制备了CoCrFeNiMo_x高熵合金涂层,研究了涂层的组织结构和耐蚀性能,并结合第一性原理计算分析了涂层耐蚀机理。研究结果表明：CoCrFeNiMo_0.1、CoCrFeNiMo_0.2高熵合金涂层是由fcc相组成,而CoCrFeNiMo_0.3高熵合金涂层则由fcc相和σ相组成。合金的晶粒主要呈树枝晶,枝晶间富集Cr、Mo元素,枝晶内富集Co、Fe元素。在3.5%(质量分数)NaCl溶液中,CoCrFeNiMo_x高熵合金涂层具有优良的综合耐蚀性能;并且随着Mo元素含量的增加,涂层的腐蚀电位正移,腐蚀电流密度减少,钝化区间变长,阻抗弧半径增大,电极反应阻力增强。通过第一性原理计算证明,涂层较高的耐蚀性能与表面致密的钝化膜形成密切相关。     

铝合金表面激光熔覆铜镍合金涂层的组织、硬度与耐蚀特性研究

为提升铝合金材料的耐蚀性能,探究铝合金与合金熔覆层间的结合机理,本文利用激光熔覆技术在5083铝合金表面制备了不同Ni含量的铜镍合金熔覆层,并利用扫描电子显微镜、X射线衍射分析、硬度测试与电化学性能测试技术,分析了不同Ni含量的铜镍合金熔覆层相组成与组织形貌、铜镍合金熔覆层与铝合金基体的界面组织形貌,绘制了铝元素扩散曲线,分析了海水腐蚀过程中铜镍合金熔覆层的极化曲线。实验结果表明：所制备的铜镍合金熔覆层形貌良好无缺陷,熔覆层由网络状枝晶组成。对合金熔覆层进行XRD分析发现熔覆层主要由AlNi₃与CuNi两相组成。结合SEM、EDS分析,发现合金熔覆层的网络状枝晶为富铝相,即AlNi₃,晶间相为CuNi相。在硬度测试中,由于AlNi₃硬质相的生成,熔覆层硬度得到了提升且随着铝的向上扩散呈现一定的规律,电化学检测结果表明,铜镍合金熔覆层具有比5083铝合金更高的自腐蚀电位和较小的自腐蚀电流密度,可以有效提升5083铝合金在海水环境中的耐蚀性。     

Fabrication of Co-Based Coatings on Titanium Alloy by Laser Cladding with CeO2 Addition

In this study, Co-based laser cladding coatings reinforced by multiple phases were fabricated on titanium alloy. Co42 Co-based self-fluxing alloy, B₄C, and CeO₂ mixed powders were used as the precursor materials. The coatings were mainly composed of γ-Co/Ni, CoTi₂, CoTi, NiTi, TiC, Cr₇C₃, TiB₂, and TiB phases. A typical TiB₂/Cr₇C₃/TiC composite structure was chosen. It was found that CeO₂ did not influence the phase types of the coating significantly, but was effective in refining the microstructure and enhancing the microhardness and dry sliding wear resistance. Compared with the Ti-6Al-4V titanium alloy, the microhardness and wear resistance of the composite coatings were enhanced by 3.44–4.21 times and 14.26–16.87 times, respectively.     

Microstructural characterisation of nanocomposite nc-MeC/a-C coatings on oxygen hardened Ti-6Al-4V alloy

Nanocomposite coatings are novel, important systems composed of two or more nanocrystalline, or nanocrystalline and amorphous, phases. Such coatings offer a possibility of tailoring the coating microstructure and achieving new improved properties of coated materials. In this work a duplex surface treatment, consisting of an oxygen diffusion treatment and deposition of low friction nanocomposite nc-MeC/a-C (Me = transition metal, Ti, W or Cr) coatings, was applied for improvement of the Ti-6Al-4V alloy properties. The coatings composed of nanocrystallites of transition metal carbides (TiC or Cr_xC_y or WC) embedded in hydrogen-free amorphous carbon (a-C) matrix were deposited onto the surface of an oxygen hardened Ti-6Al-4 V alloy substrate by means of a simple DC magnetron sputtering. A nano/microstructure of the substrate material and coatings has been examined by scanning- and transmission electron microscopy complemented with the results of X-ray diffraction analyses.It was found that the nanocomposite coatings are composed of different carbide nanocrystals (with sizes of a few nanometres) embedded in an amorphous carbon matrix. The results of qualitative and quantitative analyses of the nanocrystalline phase in the coatings with use of high-resolution transmission electron microscopy combined with image analysis are given in the paper.An effect of the nano/microstructure parameters of the coated alloy onto its micro-mechanical (nanohardness and Young's modulus) and tribological properties (wear resistance and friction coefficient) is discussed in the paper.     

Effect of high dilution on the in situ synthesis of Ni–Zr/Zr–Si(B,C) reinforced composite coating on zirconium alloy substrate by laser cladding

High dilution of transition metals was employed as a new idea for in situ synthesis of Ni–Zr/Zr–Si(B, C) reinforced composite coatings by high power diode laser (HPDL) cladding Ni–Cr–B–Si powders on zirconium substrate. Microstructure, phase composition, the mechanism of in situ synthesis reinforcement and the microhardness of coatings were investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and micro-sclerometer. The results reveal that the morphologies and phase constituents are related to the content of alloying elements in powders. In low alloy coatings, the matrix was mainly composed of intermetallic compounds including NiZr and Ni₁₀Zr₇, while the reinforcements consisted of Zr₅Si₄, β-ZiSi, α-ZrSi and ZrC. At the top of high alloy coatings, the matrix was partially comprised of Zr-based amorphous phase with the reinforcements containing ZrB₂. It is thermodynamically favorable for ZrB₂ ceramic reinforcement to form compared to ZrC phase. The microstructure evolution was dependent on the contribution of the high dilution zirconium alloy substrate to the in situ reinforcement synthesis. The microhardness of the coating showed clear improvement compared with zirconium alloy substrate, although high variability was also found.     

激光铝热还原法制备Al2O3/Ti-Al基复合涂层

利用Al和TiO₂之间的放热化学反应, 采用激光原位合成技术在TC4钛合金基体材料表面制备了Al₂O₃/Ti-Al金属间化合物基复合涂层。对比分析了激光功率、激光束扫描速度和光斑尺寸变化对激光能量密度变化量的影响程度, 借助X射线衍射仪(XRD)、光学显微镜(OM)、能谱仪(EDS)和显微硬度计分别考察了激光束扫描速度对复合涂层表面宏观形貌、截面显微组织结构和显微硬度的影响。结果显示, 扫描速度的变化对激光能量密度变化量的影响程度最大, 光斑尺寸次之, 激光功率的变化影响最弱。随着激光束扫描速度的增大, 复合涂层表面渐趋粗糙, “鱼鳞纹”状形貌特征趋于明显, 复合涂层与基材结合区厚度减小。激光原位复合涂层主要由k-Al₂O₃和α-Al₂O₃增强相与α-Ti和α₂-Ti₃Al基体相组成。随着激光束扫描速度增大, 复合涂层内k-Al₂O₃部分转变为α-Al₂O₃, Al₂O₃增强相有由枝晶状向纤维状转变的趋势; 复合涂层截面显微硬度自基体至涂层表面过度平缓, 且涂层区显微硬度分布均匀, 明显高于基材平均显微硬度。     

Characterization of Gradient Ni-Fe/SiC Composite Coating on Mild Steel by Thermal Spraying in Combination with Laser Cladding

0 IntroductionMetal matrix composites(MMCs)can usuallyprovide a high stiffness to weight ratio and high wearresistance,and a material with a surface MMC hasthe potential to develop these properties on its sur-face[1].And laser cladding has been found to be anefficient technique to prepare MMC coatings on thesubstrates such as Al-based alloy,steel,brass andbronze[2~4].Among various MMC coatings preparedby laser cladding,those reinforced with oxides(mainly Al2O3)and carbides(TiC,SiC,B4C,…     

轮轨试样Co基合金激光熔覆层组织及磨损性能

为提高轮轨材料的耐磨性降低轮轨磨损,利用CO2多模激光器在轮轨试样表面获得Co基合金熔覆层,测试分析了其组织结构性能和显微硬度,利用MMS-2A微机控制摩擦磨损试验机对比研究了激光熔覆处理与未处理轮轨试样的抗磨损性能.结果表明:激光熔覆处理后在轮轨试样表面获得与基体良好结合厚度约1 mm的熔覆层;熔覆层主要由枝晶(γ-Co)和共晶组织(Cr23C6+γ-Co)构成,初生相为γ-Co过饱和固溶体,富含Cr元素,共晶组织中富含Co元素;结合区为粗大柱状晶,从中部到表层出现胞状晶、树枝晶等多种形态.离界面越远组织越细密,组织生长方向紊乱;结合区存在元素扩散,尤其是Fe、Cr和Co含量变化显著;激光熔覆Co基合金后轮轨试样硬度分别提高约52.98%和43.44%,能有效降低对摩副磨损,轮轨抗磨损能力提高约为原来的5倍.     

Structure characterization of a laser-processed Al–Mo alloy

The surface structure of a laser-processed Al–Mo alloy has been characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffractory (XRD). The alloy was prepared by first laser alloying a mixture of Al and Mo powders into an Al substrate and then laser remelting the alloyed surface. Following the first laser alloying process, the needle-like equilibrium phases (Al5Mo(h) and Al5Mo(r)) are formed with a broad size ranges and distribute inhomogeneously in the -Al solid solution matrix. This coarse structure is replaced by a finer, uniform dispersion of dendrites after the subsequent laser remelting. Four basic types of solid states precipitates are observed: (1) irregularly shaped particles constructing the dendrites and having a nearly Al5Mo stoichiometry; (2) needle-like particles which is the Al5Mo (r) phase; (3) Faceted particles having a cubic structure with a stoichiometry close to Al7Mo; (4) tiny, equi-axed particles, with a rather narrow particle size distribution and a cubic structure. © 1998 Chapman & Hall