激光熔覆FeCrNiMnMoxB0.5高熵合金涂层组织与耐蚀性能

为了获得性能优异的涂层材料,采用激光熔覆的方法在Q235钢基体上制备了不同Mo含量的FeCrNiMnMoB0.5系高熵合金涂层,着重探究Mo对高熵合金组织与性能的影响。通过金相、X射线衍射、扫描电镜、硬度计、电化学工作站分别研究了高熵合金涂层的显微组织、相结构、显微硬度及耐蚀性能。结果表明：FeCrNiMnMoB0.5系高熵合金组织为树枝晶,主要由fcc相和少量金属间化合物构成。当添加少量Mo时,涂层的硬度较低,为290 HV,随着Mo的增加,晶格畸变加剧,出现少量金属化合物,涂层硬度最大增加到658 HV。在模拟饱和盐水泥浆溶液中FeCrNiMnMo0.4B0.5表现出较好的耐腐蚀性。     

Si,Al对激光熔覆MoFeCrTiW高熵合金涂层组织性能的影响

为了提高材料表面的耐磨性和高温抗氧化性,利用激光熔覆技术在Q235钢表面制备了MoFeCrTiW高熵合金涂层,并采用X射线衍射仪(XRD)、扫描电镜(SEM)和磨损试验机等研究了Si,Al添加对高熵合金涂层组织、相结构、耐磨性和高温抗氧化性能的影响。结果表明:激光熔覆MoFeCrTiW高熵合金涂层组织为等轴晶,单独添加等物质的量的Si或Al时,涂层分别为共晶组织或树枝晶,同时添加等物质的量的Si和Al时,涂层组织为细小的等轴晶。各高熵合金涂层的主体相均为BCC相,随着Si,Al的添加,BCC相的晶格常数减小。添加等物质的量的Al有助于抑制涂层中金属间化合物的形成,使涂层耐磨性降低;添加等物质的量的Si则会形成含Si的金属间化合物和一些未知相,提高涂层耐磨性。激光熔覆MoFeCrTiW高熵合金涂层在800℃的抗氧化性较高,Si、Al的添加可使涂层的高温抗氧化性进一步提高。     

碳化钨对激光熔覆高熵合金的影响

为了获得高性能的涂层材料,采用激光熔覆的方法,在Q235钢基体上制备了FeSiCrCoMo高熵合金涂层, 并研究了WC对高熵合金涂层的组织和性能的影响。通过金相、X射线衍射、扫描电镜、硬度计、磨损试验机分别研究了添加WC前后涂层的微观形貌、相结构、硬度及磨损性能。结果表明：高熵合金FeSiCrCoMo涂层组织为粗大枝状晶,主要由BCC相和金属间化合物构成,添加WC后,涂层中形成了致密细小的胞状晶,同时BCC相增多,金属间化合物明显减少;添加WC后涂层的硬度明显增强,平均硬度提升了23%,涂层表面平均硬度达到了687 HV0.2;WC的添加使得涂层的摩擦系数减小,磨损率减小,耐磨性能提高。     

激光熔覆铜锰合金选择性脱合金制备纳米多孔涂层的研究

本文通过激光加工结合电化学腐蚀脱合金法, 成功实现了纳米多孔涂层的制备. 采用激光熔覆首先在45钢表面制备了成形良好、稀释率低的铜锰合金熔覆层, 并通过快速重熔工艺实现了初始材料组织细化. 研究表明, 在不同的电解液下,铜锰合金的临界腐蚀电位出现了明显的偏移; 在不同的腐蚀电流下,铜锰合金腐蚀后的形貌迥异. 最终,通过选择性腐蚀成功实现了纳米多孔铜和纳米多孔锰涂层的制备, 并利用电位-pH图对脱合金的选择性腐蚀进行了详细的理论解释.     

金属陶瓷复合涂层的激光熔覆与无裂纹的实现

鉴于传统的激光熔覆金属陶瓷复合涂层技术主要存在2方面不足：其一,熔覆效率低,导致大面积熔覆时成本昂贵;其二,由于激光熔覆本身的特点,即快速加热与快速凝固,在激光熔覆过程中,热应力极易诱导熔覆层开裂。基于此,综述了国内外激光熔覆金属陶瓷复合涂层的研究进展,指出其存在的主要问题,并提出了激光感应复合快速熔覆的新方法,即感应预热基材的同时快速激光熔覆。该方法不仅可使熔覆效率大大提高而且获得了无裂纹的金属陶瓷复合涂层。     

稀土CeO_2对镍基纳米Al_2O_3激光熔覆复合涂层组织和性能的影响

采用激光熔覆技术在45钢基体上制备了不同CeO2含量的镍基纳米Al2O3复合涂层,对熔覆层进行了微观组织分析和显微硬度测试。结果表明,随着CeO2含量的增加,熔覆层组织由亚共晶向共晶组织转变;加入1.0%CeO2对镍基纳米Al2O3熔覆层的组织起到明显的细化和净化作用,枝晶生长的方向性减弱,组织趋向均匀,熔覆涂层的显微硬度值比未加稀土的涂层提高了60-95HV0.2。     

斜齿轮激光熔覆Fe基合金组织与性能研究

采用激光熔覆技术在斜齿轮钢表面制备Fe基熔覆层.通过光学显微镜、显微硬度计对熔覆层进行金相组织与显微硬度分析,采用磨损机对熔覆层和基材进行摩擦实验.结果表明:当激光功率为750W,送粉速率为20g/min,扫描速度10mm/s,离焦量为16.4mm时,铁基熔覆层与基体结合界面有明显的白亮带,激光熔覆效果较好,熔覆层的显...     

磁场辅助激光熔覆制备Ni60CuMoW复合涂层

采用磁场辅助激光熔覆技术,在Q235钢表面制备了Ni60CuMoW复合涂层,借助SEM,EDS 和XRD 等表征手段对涂层进行了微观组织和物相分析,利用维氏硬度计测试了复合涂层截面的显微硬度分布,通过摩擦磨损实验和电化学测试系统研究了复合涂层的磨损性能和耐腐蚀性能。研究结果表明：涂层主要由-Ni,Cu）固溶体、硅化物和硼化物组成,Cr3Si晶粒细化且均匀致密;磁场辅助作用下,激光熔覆涂层平均显微硬度达到913HV0.5,为无磁场辅助涂层的1.5 倍,磨损失重仅为无磁场涂层的36%,自腐蚀电位上升了100 mV,腐蚀电流密度降低了70%,耐磨耐蚀性能得到了显著改善。     

激光熔覆TiC陶瓷涂层的组织和摩擦磨损性能研究

采用激光熔覆技术在TC4合金表面上制备了TiC陶瓷涂层,分析了熔覆层的微观组织,测试了熔覆层的硬度和摩擦磨损性能。结果表明:TiC激光熔覆层分为熔覆区和稀释区两个区域,熔覆区未受到基底的稀释,由TiC颗粒和TiC树枝晶组成;稀释区受到了基底的稀释,由TiC树枝晶和钛合金组成;TiC激光熔覆层的显微硬度在HV700~1500之间,明显地改善了TC4合金表面的摩擦和磨损性能。     

钛合金表面激光熔覆TiC_p/Ni基合金复合耐磨涂层

采用激光熔覆技术在TC4合金表面制备TiC颗粒增强的Ni基合金复合材料涂层,测试了熔覆层的硬度和滑动摩擦磨损性能,分析了熔覆层的强化机制。结果表明,熔覆层中存在颗粒强化、固溶强化和细晶强化等多种强化作用,熔覆层的显微硬度达HV900～1100,耐磨性能比TC4合金显著提高。     

Microstructure and properties of 6FeNiCoSiCrAlTi high-entropy alloy coating prepared by laser cladding

The content of each constituent element in the newly developed high-entropy alloys (HEAs) is always restricted in equimolar or near-equimolar ratio in order to avoid the formation of complex brittle phases during the solidification process. In this study, a 6FeNiCoSiCrAlTi high-entropy alloy coating with simple BCC solid solution phase has been prepared by laser cladding on a low carbon steel substrate. The microstructure, hardness and magnetic properties have been investigated. The experimental results show that the tendency of component segregation in the conventional solidification microstructure of multi-component alloy is effectively relieved. The microstructure of the coating is mainly composed of equiaxed polygonal grains, discontinuous interdendritic segregation and nano-precipitates. EBSD observation confirms that the polygonal grains and interdendritic segregation have similar BCC structure with lots of low angle grain boundaries at the interface. The microhardness of the coating reaches 780 HV_0.5, which is much higher than most of the HEAs prepared by other methods. In addition, the coating shows excellent soft magnetic properties.     

Characteristics of cobalt-based alloy coating on tool steel prepared by powder feeding laser cladding

Co-based alloy coating was deposited on tool steel by powder feeding laser cladding. Sections of such coatings were examined to reveal their microstructures and phases using scanning electron microscope (SEM) and X-ray diffractometer (XRD). The results showed that the prime phase (γ-Co dendrite) and other phases, including Cr₂₃C₆, Co₇W₆, and CrNi existed in the coatings. Some different solidification morphologies, such as planar (at the interface), cellular and dendrite formed, varying from the interface to the surface. Fine microstructures of γ-Co dendrite and lamellar eutectic in dendritical regions strengthened the coatings. Besides, the effects of aged treatment on the microstructure and microhardness of the surface coating were studied. Aged treatment led to the precipitations of some carbide particles (Cr₇C₃ and Co₃C) and boride particles (Co₄B) from the cladded coating, causing an increase in microhardness in the laser-cladded coating.     

Exceptionally high cavitation erosion and corrosion resistance of a high entropy alloy

Cavitation erosion and corrosion of structural materials are serious concerns for marine and offshore industries. Durability and performance of marine components are severely impaired due to degradation from erosion and corrosion. Utilization of advanced structural materials can play a vital role in limiting such degradation. High entropy alloys (HEAs) are a relatively new class of advanced structural materials with exceptional properties. In the present work, we report on the cavitation erosion behavior of Al_0.1CoCrFeNi HEA in two different media: distilled water with and without 3.5 wt% NaCl. For comparison, conventionally used stainless steel SS316L was also evaluated in identical test conditions. Despite lower hardness and yield strength, the HEA showed significantly longer incubation period and lower erosion-corrosion rate (nearly 1/4th) compared to SS316L steel. Enhanced erosion resistance of HEA was attributed to its high work-hardening behavior and stable passivation film on the surface. The Al_0.1CoCrFeNi HEA showed lower corrosion current density, high pitting resistance and protection potential compared to SS316L steel. Further, HEA showed no evidence of intergranular corrosion likely due to the absence of secondary precipitates. Although, the degradation mechanisms (formation of pits and fatigue cracks) were similar for both the materials, the damage severity was found to be much higher for SS316L steel compared to HEA.     

H13钢激光熔覆Co基涂层组织及热疲劳性能

针对热作模具用H13钢工况下易产生热疲劳失效的问题,采用Nd:YAG激光器在H13钢表面制备Co基合金涂层。利用光学显微镜、扫描电镜、能谱仪和X射线衍射仪,对涂层组织、合金元素分布及物相组成进行检测。利用显微硬度计和热震实验法,测试热疲劳对Co基合金涂层和淬火回火态H13钢硬度影响。结果表明,Co基合金涂层从底部到表层,依次为平面晶、胞状晶、树枝晶和等轴晶。Co基合金涂层物相主要由-Co和M23C6相组成,热疲劳后涂层表面形成M2O3和M3O4(M=Fe,Co,Cr)氧化物。Co基合金涂层硬度最高可达706HV0.2且呈梯度降低;热循环1000次后,Co基合金涂层表面硬度降低24.4%,H13钢表面硬度降低37.7%,Co基合金涂层硬度下降幅度低于H13钢。热循环1000次后,Co基合金涂层表面未发现明显热裂纹,H13钢表面形成大量网状热裂纹。Co基合金涂层中,Cr元素形成致密Cr2O3氧化膜使其热疲劳性能优于H13钢。     

H13钢激光熔覆Co基涂层组织及热疲劳性能

针对热作模具用H13钢工况下易产生热疲劳失效的问题,采用Nd:YAG激光器在H13钢表面制备Co基合金涂层。利用光学显微镜、扫描电镜、能谱仪和X射线衍射仪,对涂层组织、合金元素分布及物相组成进行检测。利用显微硬度计和热震实验法,测试热疲劳对Co基合金涂层和淬火回火态H13钢硬度影响。结果表明,Co基合金涂层从底部到表层,依次为平面晶、胞状晶、树枝晶和等轴晶。Co基合金涂层物相主要由-Co和M23C6相组成,热疲劳后涂层表面形成M2O3和M3O4(M=Fe,Co,Cr)氧化物。Co基合金涂层硬度最高可达706HV0.2且呈梯度降低;热循环1000次后,Co基合金涂层表面硬度降低24.4%,H13钢表面硬度降低37.7%,Co基合金涂层硬度下降幅度低于H13钢。热循环1000次后,Co基合金涂层表面未发现明显热裂纹,H13钢表面形成大量网状热裂纹。Co基合金涂层中,Cr元素形成致密Cr2O3氧化膜使其热疲劳性能优于H13钢。     

铁基合金激光熔覆层高温润滑磨损性能

为提高40Cr合金钢的表面耐磨性,采用预置激光熔覆法在40Cr基体表面制备铁基合金涂层, 利用扫描电镜观察分析熔覆层显微组织形貌,用显微硬度仪测试熔覆层截面显微硬度,用摩擦磨损试验机测定在润滑条件下基体、熔覆层的摩擦系数随温度变化的规律。研究结果表明:熔覆层与基体实现良好冶金结合,熔覆层横截面微观组织呈现平面晶、树枝晶和胞状晶分布;熔覆层硬度值介于617.5~926.6 HV0.2之间,基体硬度介于205.2~278.2 HV0.2之间;在200 ℃以下,熔覆层摩擦系数在磨程中趋于平稳,在0.1附近轻微波动,小于基体平均摩擦系数;当温度超过200 ℃,油膜分解,引发润滑失效,磨损方式向干摩擦转化,磨损机理从微切削磨损主导向粘着磨损、磨粒磨损和氧化磨损复合磨损方式转化。     

Effect of scanning speeds on electrochemical corrosion resistance of laser cladding TC4 alloy

In order to study the effect of scanning speed on the electrochemical corrosion resistance of laser cladding TC4 alloy in artificial seawater, the x-ray diffraction analysis, microstructure of cross-section, microhardness variation, and impedance spectrum have been studied in comparison with the TC4 titanium alloy. The results show that the main phase of cladding coating is α-Ti, and the change of scanning speed has no obvious effect on it; therefore, the supersaturated α-Ti solid solution is formed, and the acicular α martensite is obtained. As the scanning speed increases, the microstructure of cladding coating is orthogonal basket-weave, the crystal surface spacing decreases, and the average microhardness of laser cladding TC4 alloy slightly increases. When the scanning speed increases to 10 mm/s, the microhardness is about 14.71%higher than that of the substrate, and the electrochemical corrosion resistance of laser cladding TC4 alloy is also improved,which is about 2.48 times more than the substrate. Grain refinement has a great effect on enhancing the anti-electrochemical corrosion.     

In-situ synthesis of Fe-Mn-Si-Cr-Ni shape memory alloy functional coating by laser cladding

Fe-Mn-Si-Cr-Ni composite powders are utilized to form a functional shape memory alloy cladding layer(SMACL)using a laser cladding method.The microstructure,microhardness,and phase composition of the SMACL are measured,and the extent of deformation of the laser cladding samples is determined.The SMACL is composed of planar,cellular,and dendritic crystals,equiaxed grains,and oxides with increasing distance from the substrate surface.The SMACL is further composed ofε-martensite andγ-austenite phases,while the tempered SMACL consists mainly ofγ-austenite.Extensive deformation occurs in AISI304 stainless steel laser cladding samples.By contrast,limited deformation is observed in the SMACL samples.