铸铁表面激光熔敷层的抗裂性和耐磨性

采用免预热多道搭接的激光熔敷工艺，在铸铁表面制备出抗裂耐磨的激光熔敷层，研究了激光功率和扫描速度对熔敷层抗裂性的影响。适当的激光功率和扫描速度可以使铁基熔敷层的裂纹率最低．随着Ni含量的增加，熔敷层内奥氏体相体积分数增加；K可促进共晶碳化物团球化，熔敷层抗裂性增强．通过对铸铁表面激光熔敷层裂纹的萌生与扩展的动态观察，揭示了熔敷层开裂的微观机制．裂纹易在粗大渗碳体区或石墨与奥氏体的界面处萌生，奥氏体可明显抑制裂纹的扩展．Ti含量增加使熔敷层中原位自生的TiC的体积分数增大，熔敷层磨损质量损失减少，耐磨性增强．     

铸铁表面激光熔敷镍基合金涂层的耐磨性研究

为了提高铸铁的耐磨性，以35％WC和不含WC的镍基合金粉末为原料对铸铁表面进行激光熔敷处理，利用XRD、SEM、TEM等技术分析了涂层的成分及显微组织结构，并测试了涂层的耐磨性和硬度．结果表明：激光处理后表面迅速熔化和冷却，组织由珠光体 片状石墨组织转化为不同粗细的针状马氏体与残余奥氏体组织；熔敷层的耐磨性和硬度明显提高，且添加35％WC硬质颗粒的熔敷层硬度最高值不在最表层，而在距表面约0．2mm处；合金涂层在磨损机制下表现为犁沟切削、微切削以及硬相质点的剥落，不同基体划痕形式不同。     

工艺因素对激光熔敷层裂纹率的影响

研究了试板体积、熔敷层长度、搭接量、溶敷层搭接道数及压板拘束对熔敷层裂纹率的影响，结果表明随试板体积增大、熔敷层长度增加、搭接量增大和熔敷层搭接道数增多，熔敷层裂纹率升高。压板及冷却水的拘束作用也使熔敷层裂纹率升高。分析并比较了上述工艺因素作为熔敷层抗裂性判据的优劣，其中熔敷层道数对裂纹率影响更加直观、简便和准确，最终获得了评定熔敷层抗裂性优劣的最佳判据和补充判据。     

工艺因素对激光熔敷层裂纹率的影响

研究了试板体积、熔敷层长度、搭接量、熔敷层搭接道数及压板拘束对熔敷层裂纹率的影响 ,结果表明随试板体积增大、熔敷层长度增加、搭接量增大和熔敷层搭接道数增多 ,熔敷层裂纹率升高。压板及冷却水的拘束作用也使熔敷层裂纹率升高。分析并比较了上述工艺因素作为熔敷层抗裂性判据的优劣 ,其中熔敷层道数对裂纹率影响更加直观、简便和准确 ,最终获得了评定熔敷层抗裂性优劣的最佳判据和补充判据。     

激光熔敷Ni基WC合金

为强化工矿用鼓风机叶片性能,在15MnV 钢表面火焰喷涂 Ni 基 WC 合金,而后采用激光熔敷工艺,控制激光辐照条件和熔化深度,获得了细密的敷层组织。用近代测试手段对熔敷层的组织、结构以及敷层的性能进行了分析研究。采用后续热处理使激光熔敷层组织分布趋于合理化,为激光熔敷这一新工艺的实用化奠定了一定的基础,并为提高风机叶片的使用寿命开辟了一条新途径。     

金属雾化喷嘴表面热障涂层结构特征研究

采用5KW连续CO2激光器对经等离子喷涂的NiCoCrAlY结合层和ZrO2陶瓷层进行二次重熔处理，并利用金相显微镜，扫措电镜和电子探针对激光熔敷涂层进行了显微结构和元素分布观察与测试，结果表明：激光熔敷涂层中基体对NiCoAlY合金层产生稀释，形成成分和组织偏析。加入了TiO2-Al-Ti添加剂的ZrO2陶瓷层激光重熔后得到了无裂纹的定向生长柱状晶，并且呈现一次枝晶平均间距为2．3μm的表层和平均间距为3．8μm的次表层结构。     

45~#钢激光熔敷Ni基合金层的性能研究

研究了４５＃钢激光熔敷镍基合金层后表面性能变化。对熔敷层的组织观察、硬度测试、电子探针分析、磨损及冷热疲劳试验结果表明，材料的表面性能，包括硬度、耐磨性、抗冷热疲劳性能等都得到了很大地提高。     

激光熔覆Stellite和WFLC系列钴基粉末研究

用TJ－HL－5000 CO2激光器对4种不同Co基材料进行了激光熔覆研究,对熔覆层抗裂性进行了对比,分析了合金元素对熔覆层抗裂性的影响,指出WFLC－08及WFLC－11两种材料具有较高的抗裂性和耐磨性,是能满足激光熔覆工艺要求的Co基合金粉末材料。     

不同保护Ar气含量下304不锈钢熔敷组织演变及夹杂物特征分析

为了提高304不锈钢熔敷组织的质量,选择Ar气对实心焊丝提供保护,并试验测试分析了不同保护Ar气含量对304不锈钢熔敷组织及夹杂物性能的影响。研究结果表明:当Ar在保护气内的含量降低后,熔敷层硬度减小,冲击韧性随温度升高呈现先上升后下降的趋势,屈强比先减小后增大。当保护气内存在80%的Ar后,获得了具备优异力学特性的熔敷层。熔敷层组织中存在较多的马氏体组织以及部分条状奥氏体组织,条状马氏体中形成了大量的位错结构。当Ar含量达到96%时,熔敷层生成了许多颗粒以及条形的碳化物,每个柱状晶中都形成了几乎呈平行排列状态的板条块结构。当Ar的含量降低后,夹杂物尺寸与数量都上升。当保护气内的Ar含量达到80%时,在熔敷层内形成了更多的有助于促进铁素体形核的杂质。所有熔敷层内形成的夹杂物都是由氧化物以及部分硫化物构成的夹杂物,靠近中心部位的Al与Ti含量更高。     

45钢表面高频感应高铬铸铁熔敷层的组织结构及性能

铁基合金熔敷层可提高钢铁等基体的耐磨、耐蚀等性能0采用高频感应熔敷工艺在45钢基体表面制备了Fe60（高铬铸铁型）铁基熔敷层,通过金相显微镜、扫描电镜（SEM）、能谱仪、显微硬度计、X射线衍射仪（XRD）研究了熔敷层的形貌、成分、相结构、硬度、耐蚀性。结果表明：熔敷层致密,厚1．8mm,与基体呈冶金结合,由马氏体相C0...     

激光熔覆涂层与热喷涂涂层组织性能比较

分别采用激光熔覆与火焰喷涂两种技术在38CrMoAl基体表面制备NiCrBi WC(wt20%)合金涂层,比较其组织结构及其硬度分布,试验表明：激光熔覆涂层无缺陷,成品率高,组织细密均匀,晶粒细小,硬度高,对基体热影响小,与基体结合为成分缓慢过渡的冶金结合。     

A preliminary study of laser cladding of AISI 316 stainless steel using preplaced NiTi wire

NiTi wire of diameter 1 mm was preplaced on AISI 316 stainless steel samples by using a binder. Melting of the NiTi wire to form a clad track on the steel substrate was achieved by means of a high-power CW Nd:YAG laser using different processing parameters. The geometry and microstructure of the clad deposit were studied by optical microscopy and scanning electron microscopy (SEM), respectively. The hardness and compositional profiles along the depth of the deposit were acquired by microhardness testing and energy-dispersive spectroscopy (EDS), respectively. The elastic behavior of the deposit was analyzed using nanoindentation, and compared with that of the NiTi wire. The dilution of the NiTi clad by the substrate material beneath was substantial in single clad tracks, but could be successively reduced in multiple clad layers. A strong fusion bonding with tough interface could be obtained as evidenced by the integrity of Vickers indentations in the interfacial region. In comparison with the NiTi cladding on AISI 316 using the tungsten inert gas (TIG) process, the laser process was capable of producing a much less defective cladding with a more homogeneous microstructure, which is an essential cladding quality with respect to cavitation erosion and corrosion resistance. Thus, the present preliminary study shows that laser cladding using preplaced wire is a feasible method to obtain a thick and homogeneous NiTi-based alloy layer on AISI 316 stainless steel substrate.     

镁合金表面激光熔覆的研究现状

综述了AZ91镁合金表面Al基合金熔覆层、Cu基合金熔覆层、复合材料熔覆层、陶瓷熔覆层、非晶熔覆层等不同激光熔覆层的组织特征和耐磨耐蚀性的研究现状,比较了各类熔覆层的优缺点,并对镁合金激光熔覆今后的研究重点提出了几点建议。     

铁含量对激光熔覆层微结构及性能的影响

为满足不同支承辊再制造表面硬度需求,利用激光熔覆技术,将添加不同含量纯铁粉的铁基合金粉末材料熔覆到Cr5支承辊钢表面。研究了铁含量对熔覆层微结构及性能的影响。结果表明,所有材料设计成分条件下熔覆层的截面组织差异很小,均为鱼骨状枝晶和网状晶间组织。通过改变添加铁粉的量可以控制熔覆层中枝晶含量。随着合金粉末中铁含量增多,激光熔覆层截面硬度和耐磨性显著下降。添加50%(质量分数)纯铁粉的粉末材料可以制备出硬度约为480HV、耐磨性高于传统淬火工作层的激光熔覆层,可以满足Cr5支承辊再制造需求。     

Co800基激光熔覆/重熔增强多物相复合层组织及耐磨性能

目的 增强钛合金表面耐磨损性能。方法 采用激光熔覆与激光重熔技术在TC4钛合金表面制备Co800–Si₃N₄–YPSZ(Y₂O₃部分稳定ZrO₂)与Co800–Si₃N₄–YPSZ–MGOSs(单层氧化石墨烯薄片)复合层,并对熔覆层及重熔层微观组织结构、元素分布及耐磨损性能进行分析。结果 细晶强化作用改善了Co800–Si₃N₄–YPSZ–MGOSs熔覆层的耐磨性。激光重熔后,在熔池快速冷却过程中产生了非晶–纳米晶相,促进了多物相重熔层形成。MGOSs受热分解释放了C,在熔池中原位生成了Ti(CN)。结论 含有Ti₅Si₃、TiN及TiC等多种硬质增强相的Co800–Si₃N₄–YPSZ–MGOSs熔覆层的摩擦因数较TC4的摩擦因数降低,其磨损体积约为TC4磨损体积的1/7。     

Finite-element analysis of selectively SiC fibre-reinforced titanium composites

Finite element analysis has been applied to selectively SiC fibre reinforced titanium matrix composites. The influence of thermal residual stress on the behaviour of clad titanium fibre composites with initial unbridged sharp cracks under external loading has been investigated. Through-thickness stress distributions have been obtained for the composites as a function of loading configuration, fibre volume fraction, cladding thickness and composite thickness. It has enabled a quantitative understanding of the premature delamination of clad titanium fibre composites ahead of mode I crack that has been observed experimentally. Potential solutions to the problem have been suggested based on finite element predictions of the variation of tensile through-thickness stress close to the transition boundary between cladding material and composite as a function of fibre volume fraction and, especially, with thickness of the cladding layers.     

Effect of Copper and Bronze Addition on Corrosion Resistance of Alloyed 316L Stainless Steel Cladded on Plain Carbon Steel by Powder Metallurgy

A sandwich structure with cladding alloyed 316L stainless steel on plain carbon steel was prepared by means of powder metallurgy (PM) processing. Electrolytic Cu and prealloyed bronze (95Cu wt pct, 5Sn wt pct) were added in different contents up to 15% into the surface cladded 316L layers and the effect of alloying concentrations on the corrosion resistance of the 316L cladding layers was studied. The corrosion performances of the cladding samples were studied by immersion tests and potentio-dynamic anodic polarization tests in H_2S0_4 and FeCl_3 solutions. Both 316L and alloyed 316L surface layers with 1.0 mm depth produced by PM cladding had an effect to improve corrosion resistance in H2SO4 and FeCI3 solutions. Small Cu and bronze addition (4%) had a positive effect in H_2SO_4 and FeCl3 solutions. 4% Cu alloyed 316L surface layer produced by PM cladding showed similar anodic polarization behaviour to the 316L cladding layer in H_2SO_4 and FeCl_3 solutions.     

FINITE ELEMENT AND EXPERIMENTAL STUDIES OF CRACK GROWTH IN CLADDED SEN(B) SPECIMENS

Abstract— The transferability of fracture results between homogeneous and cladded specimens was studied in single edge-notched bend specimens. The test material was of A533-B steel with a clad layer deposited by a commercial strip welding process. The fracture resistance properties were developed independently for cladding and base material using homogeneous specimens of each material. The experimental data from tests on cladded specimens were analysed with the finite element method. The 3D J -values were compared with values evaluated using the measured crack extension in the cladded specimen and the J _R-data of the respective material provided from homogeneous specimens. A reasonably good agreement was obtained in this comparison for a limited amount of crack growth.