Laser multi-layer cladding of Zr<Subscript>65</Subscript>Al<Subscript>7.5</Subscript>Ni<Subscript>10</Subscript>Cu<Subscript>17.5</Subscript> amorphous alloy on magnesium substrates

A coating about 3-mm thick of the amorphous alloy, Zr₆₅Al_7.5Ni₁₀Cu_17.5 was fabricated on magnesium substrates using the technique of laser multi-layer cladding protected under an atmosphere of argon gas. The coating exhibited a graded microstructure, which could be generally categorized into three classes: an amorphous phase, an amorphous–nanocrystalline composite, and one which is predominantly crystalline. Formation of the latter two was due to the reheating effect of the laser cladding process. With regard to properties, the microhardness and the wear resistance of the composite material were both higher than that of the monolithic amorphous material; both materials showed excellent corrosion resistance in a 3.5% NaCl solution.     

SiC含量对激光熔覆SiC/Ni60A复合涂层显微组织和耐磨性能的影响

利用LDM2500-60半导体激光器在45#钢板上制备SiC颗粒增强Ni60A合金激光熔覆涂层,系统研究SiC含量对涂层的显微组织、稀释率、耐磨性、摩擦因数和显微硬度的作用规律。结果表明:随着SiC含量增加,熔覆表层的微观组织细化,稀释率、耐磨性、摩擦因数和硬度均先增加后降低;当SiC含量为20%(质量分数,下同)时,熔覆层的耐磨性能最佳,磨损量仅为0.0012g,为基体磨损量的1/36.3;摩擦因数最小为0.464,且磨损过程最为平稳;熔覆层平均硬度值最高,达到1039.9HV0.2,为基体的3.5倍;但当SiC含量达到25%时,熔覆层的显微硬度与耐磨性能反而下降。     

Research on in situ synthesised (Ti,V)C/Fe composite coating by laser cladding

Laser cladding is an effective way to improve the wear resistance of mechanical components. In this study, the composite carbide (Ti,V)C reinforced Fe based coating was successfully synthesised by laser cladding the powder mixtures of ferrotitanium, ferrovanadium and graphite. The samples were analysed to assess the microstructure, microhardness and wear properties. Results indicate that high quality composite coating with metallurgical joint to the steel substrate was obtained. During laser cladding processes, it is found that the (Ti,V)C composite particles were in situ synthesised and distributed evenly in the coating. The microhardness and wear properties of the clad coating were improved significantly in comparison to the steel substrate due to the presence of the hard reinforcement (Ti,V)C.     

Laser cladding composite coatings by Ni–Cr–Ti–B4C with different process parameters

To investigate the effect of laser process parameters on microstructure and properties of composite coating, the composite coatings were manufactured by laser cladding Ni–Cr–Ti–B₄C mixed powder on Q235 mild steel with different process parameters. The coatings are bonded with the substrate by remarkable metallurgical binding without cracks and pores. The composite coatings are consisted of in situ synthesized solid solution Ni–Cr–Fe, intermetallic compound (IMC) Ni₃Ti, Cr₂Ti, and ceramic reinforcements TiB₂, TiC. Results of scanning electron microscopy (SEM) revealed that the ceramic reinforcements became coarser with higher specific energy (E_s). There were independent ceramics TiB₂, TiC, eutectic ceramic TiB₂–TiC in coatings, and eutectic alloy–ceramic was detected. Compared with the substrate, the microhardness of coatings was increased significantly, and the maximum microhardness of coatings was approximately five times as high as the substrate. The wear resistance of coatings was improved dramatically than the substrate. Compared to the coatings with lower E_s, higher E_s led to lower microhardness and worse wear resistance ascribing to more Fe diffused into the coating from the substrate.     

Microstructure and properties of laser clad high-entropy alloy coating on aluminium

An AlCrFeNiCuCo high-entropy alloy (HEA) coating was synthesised on an aluminium substrate by laser cladding. Samples were characterised using an optical microscope, X-ray diffraction, scanning electron microscopy with energy-dispersive spectroscopy, a microhardness tester, and an electrochemical workstation. The results showed that the interface between the cladding layer and matrix was sound, while the HEA coating consisted of BCC and FCC solid solutions and an Al-rich phase resulting from substrate dilution. The microstructure of the clad layer comprised both columnar and equiaxed grains. The average microhardness of the coating was 550 HV_0.2, and it exhibited better corrosion resistance than the aluminium matrix in a 1?mol?L^?1 H₂SO₄ solution. The typical corrosion characteristic of the coating was pitting and localised corrosion.     

基于工业合金激光熔覆制备Fe基非晶涂层

以FeCoCrMoCBY块体合金为熔覆材料,采用激光熔覆在低碳钢表面制备非晶涂层,探讨不同激光功率对涂层成形及组织的影响,通过显微硬度仪、电化学工作站测试涂层显微硬度及耐腐蚀性能。研究结果表明,其他参数不变,激光功率为17.6~20.8 W时,涂层成形良好,与基材呈典型冶金结合。随激光功率增加,涂层稀释率升高,裂纹倾向增大,非晶化程度降低。激光功率为17.6 W时,涂层主要由非晶组成,稀释率低于24.2%,结构致密,包括热影响区、熔合区和熔覆区;涂层平均显微硬度为1 330HV,约高于基材9倍,在3.5%NaCl溶液中的耐腐蚀性能明显优于316L不锈钢。     

Effect of molybdenum on microstructure and wear properties of Fe–Ti–Mo–C laser clad coatings

Abstract

The AISI?1045 steel surface was alloyed with preplaced ferrotitanium (Fe–Ti), ferromolybdenum (Fe–Mo) and graphite powders using a 5 kW CO₂ laser. In situ carbide reinforced Fe based surface composite coating was fabricated. The results showed that (Ti,Mo)C particles with flower-like and cubic shapes were formed during laser cladding process. The growth morphology of the reinforcing (Ti,Mo)C carbide has typically faceted features, indicating that the lateral growth mechanism is still the predominant growth mode under rapid solidification conditions. Increasing the amount of Fe–Mo in the reactants led to a decrease in carbide size and an increase in volume fraction of carbide but increased the crack sensitivity of the coating. The multiple carbides of (Ti,Mo)C created a higher microhardness and excellent wear resistance than TiC alone under dry sliding wear test condition.     

Effect of cobalt content on microstructure and property of electroplated nickel‐cobalt alloy coatings

Nickel‐cobalt alloys were electrodeposited on copper sheets in sulfate bath containing 288.5 g/l NiSO₄·6H₂O, 30 g/l CoSO₄·7H₂O, 40 g/l HBO₃, 15 g/l NaCl and 0.08 g/l lauryl sodium sulfate. The effects of cobalt content on microstructure, microhardness, and wear resistance of electroplating nickel‐cobalt alloys were studied by using SEM and XRD techniques, and microhardness tester and wear tester. The relationship between the microhardness of nickel‐cobalt alloy coatings and heat treatment procedures was also investigated. The experimental results show that cobalt content (W_t) in coating increases with Co²⁺/(Co²⁺ + Ni²⁺)% (X) in plating solution. Fitted regression equation is as following: W_t = –0.7399 + 2.2847X – 0.0133X². The increase of cobalt content leads to that the longitudinal section morphology of coating transforms from the cone into sphericity and at last into the shape of willow leaf, and its structure transforms from face centered cubic (fcc) nickel solid solution into fcc cobalt solid solution and at last into hcp cobalt solid solution. The increase of cobalt content results in the increase of microhardness of nickel‐cobalt alloy coatings, and the hardness reaches a maximum value (363 HV) when cobalt content is 54.9%. After heat treatment at 400°C and 600°C, the microhardness of coatings begins to decrease except the coating containing 79.2% Co. Moreover, the wear resistance of electroplated coatings increases with the increase of cobalt content.     

Effects of TIG surface treating on microstructural characteristics and mechanical properties of Al2O3–TiB2 coating by APS

Abstract

The pulsed DC tungsten inert gas (TIG) method was employed to post-spray treat an electroconductive Al₂O₃–TiB₂ coating by atmosphere plasma spraying (APS) Al₂O₃–30 wt-%TiB₂ powder. The microstructure and mechanical properties of the coatings before and after treatment were comparatively investigated by scanning electron microscopy, laser scanning confocal microscopy, X-ray diffraction, microhardness tester and block on ring wear tester. It was detected that the treated coating presented a two layer structure consisting of the remelted zone and the sintered zone, which was comprised of TiB₂ and single α-Al₂O₃; surface roughness of the treated coating exhibited a remarkable decrease while microhardness and wear resistance showed a significant increase. These experimental results could be ascribed to the effect of high heat input and discharge plasma during the pulsed DC TIG treating.     

Microstructure and properties of laser-clad FeNiCoCrTi0.5Nb0.5 high-entropy alloy coating

ABSTRACT

FeNiCoCrTi_0.5Nb_0.5 high-entropy alloy coating is prepared on AISI 1045 steel by laser cladding. The cross-sectional macroscopic morphology, phase, microstructure, microhardness and wear resistance are studied systematically. The results show that FeNiCoCrTi_0.5Nb_0.5 coating has no porosities, cracks or other defects and is well metallurgically bonded to the substrate. The coating is composed of body-centred cubic (BCC) solid solution, face-centred cubic (FCC) solid solution and hard Laves phase. The solid solution phase and Laves phase distribute uniformly and closely in a lamellar shape to form a fine and dense eutectic structure. The microhardness of FeNiCoCrTi_0.5Nb_0.5 coating is about three times that of the substrate. Compared with the substrate, the coating has superior wear resistance.     

铝青铜表面激光熔覆镍基涂层的组织与磨损性能

为了改善铜合金表面的耐磨性能,利用超音速火焰喷涂和激光重熔技术在铝青铜上制备了镍基涂层。分析了激光熔覆层的微观组织,测试了其显微硬度及磨损性能。结果表明:熔覆层组织致密、无裂纹,与铝青铜形成了良好的冶金结合;从熔覆层表层到基体热影响区,组织呈现出由细小的柱状晶→胞状晶、树枝晶→平面晶过渡;激光熔覆层磨损量约为铝青铜的1/4,熔覆层耐磨能力的增强归因于熔覆层与铝青铜间良好的冶金结合及基体与涂层元素固溶强化和碳化物等析出相的强化作用。     

Evaluation of stellite coatings by µ-PTA powder,laser, and PTA deposition processes

This article presents comparative evaluation of microplasma-transferred arc powder deposition (µ-PTAPD), laser deposition, and plasma-transferred arc deposition (PTAD) processes for sound quality and cost-effective deposition of Stellite 6 on AISI 4130 steel substrate. Dilution, deposition thickness, microstructure, secondary dendritic arm spacing (SDAS), microhardness, and abrasive wear resistance have been used for comparative evaluation. Analysis of morphology of Stellite deposition revealed that µ-PTAPD process and laser deposition processes could produce a coating of less than 1?mm thickness having good deposition quality, smaller dilution, and SDAS as compared with PTAD process. Analysis of X-ray diffraction patterns revealed that the Stellite coatings manufactured by all three processes had a lamellar structure consisting of Co phases, chromium-rich carbides (Cr₂₃C₆ and Cr₇C₃), and tungsten-containing compounds (W₂C). Analysis of microhardness and abrasive wear resistance found that the Stellite coatings manufactured by µ-PTAPD and laser deposition processes exhibited a lower coefficient of friction, wear volume, and higher microhardness as compared with the coating manufactured by PTAD process, this imparting them with higher abrasive wear resistance. This work proves that µ-PTAPD process has a capability to offer an economical and sustainable solution for good-quality thin coating of Stellite on metallic substrates.     

激光熔覆镍基合金层的组织与高温耐磨性能

为了改善304不锈钢工件的高温耐磨性能,利用CO2激光器在其表面熔覆了Ni基高温合金层。研究了熔覆层的物相组成、显微组织、成分分布,测试了其显微硬度、高温耐磨性能等,并与基材进行了对比。结果表明:Ni基合金熔覆层的组织从熔池底部到表层为胞状晶—柱状枝晶—树枝晶;熔覆层的主要组成相是Ni3Cr2,NbC,Mo2C与Cr23C6;Ni基合金粉末中添加难熔元素Cr,Mo,Nb等对熔覆层的组织起到了固溶强化、硬质相强化和弥散强化作用;熔覆层的平均显微硬度达到了405 HV,高温耐磨性能是基体的2倍多。     

钛合金表面激光熔覆Ni基梯度涂层的研究

为了改善Ti6Al4V钛合金表面耐磨性能和抗高温氧化性能,采用CO2激光在Ti6Al4V钛合金表面进行激光熔覆Ni基梯度涂层试验.利用扫描电镜和显微硬度计等手段分析了熔覆层组织,测试了基体和熔覆层的显微硬度.结果表明,采用适当的工艺参数,可以在钛合金表面获得连续、均匀、无裂纹和气孔的熔覆层.熔覆层组织由树枝晶和晶间共晶组织构成,并与基体形成牢固的冶金结合.由基体到表面,显微硬度过渡平稳,呈明显梯度渐变特征.     

Role of preheating and specific energy input on the evolution of microstructure and wear properties of laser clad Fe-Cr-C-W alloys

Synthesis of Fe-Cr-C-W alloy (10 : 4 : 1 : 1, wt(%)) was carried out on AISI 1016 steel substrate using laser cladding technique which lead to the development of a suitable alternate for cobalt bearing wear resistant alloys. This study involved understanding of process variables like preheating temperature and specific energy input on the evolution of microstructures and their effect on wear resistance properties. The microstructure was examined with a scanning electron microscope and various types of complex carbides were identified using both energy dispersive x-ray and auger spectroscopy facilities. A combination of MC, M₇C₃ and M₆C types of carbides of certain proportions (formed at a preheating temperature of 484°C with specific energy input of 9.447 KJ/cm²) has been found to be most attractive for achieving an optimum combination of microhardness and steady state friction coefficient values. A similar advantage may be derived at a lower level of specific energy input of 8.995 KJ/cm² but with a higher preheating temperature of 694°C. However, increasing the specific energy input to 12.376 KJ/cm² can significantly soften the matrix.     

Development of wear resistant composite surface on mild steel by laser surface alloying with silicon and reactive melting

The present study concerns laser surface alloying with silicon of mild steel substrate using a high-power continuous wave CO₂ laser with an objective to improve wear resistance. The effect of surface remelting using nitrogen as shrouding environment (with and without graphite coating) on microhardness and wear resistance has also been evaluated. Laser surface alloying leads to formation of a defect free microstructure consisting of iron silicides in laser surface alloyed mild steel with silicon and a combination of silicides and nitrides when remelted in nitrogen. Carbon deposition prior to remelting leads to presence of a few martensite in the microstructure. A significant improvement in microhardness is achieved by laser surface alloying and remelting to a maximum of 800 VHN when silicon alloyed surface is melted using nitrogen shroud with carbon coating. A detailed wear study (against diamond) showed that a significant improvement in wear resistance is obtained with a maximum improvement when remelted in nitrogen atmosphere followed by carbon coating.     

Laser cladding of Zr65Al7.5Ni10Cu17.5 amorphous alloy on magnesium

Laser cladding of amorphous alloy Zr₆₅Al_7.5Ni₁₀Cu_17.5 on magnesium substrate was conducted using the blown powder method. The thickness of the coating was about 1.5 mm. The resulting microstructure, wear resistance and corrosion resistance of the coating were studied. The results of the XRD and TEM analyses showed that up to a depth of 1.1 mm, the coating had an amorphous structure, and no apparent crystalline structures were found. The coated specimen exhibited wear and corrosion resistance superior to that of the uncoated specimen: the wear loss was significantly reduced, some thirteen-fold; and the corrosion current was lowered by three orders of magnitude.     

等离子钴基熔覆层的组织和性能研究

等离子熔覆技术是采用等离子束为热源,在金属表面获得优异的耐磨、耐蚀、耐冲击等性能的新型材料表面改性技术。本工作对低碳马氏体钢表面进行等离子熔覆处理,研究钴基合金熔覆层的显微硬度、金相组织。研究结果表明:钴基合金熔覆层的硬度达942HV。熔覆层组织主要由树枝晶和孢状晶粒组成,熔覆层与基体界面结合良好,无裂纹。     

Microstructure and wear resistance of electrodeposited RE-Ni-Mo-P-B4C-PTFE composite coating

Abstract

The structure, hardness and wear resistance of RE-Ni-Mo-P-B₄C-PTFE composite coating have been studied by means of X-ray diffraction, scanning electron microscopy, abrasion testing and microhardness testing. The results show that the structure of RE-Ni-Mo-P-B₄C-PTFE composite coating experiences a transformation from amorphous via a mixture to crystalline as the heat treatment temperature is increased. Crystalline particles in the coating become gradually finer with the addition of B₄C, B₄C plus polytetrafluoroethylene (PTFE) and B₄C plus PTFE plus rare earths (RE), in that order. The hardness and wear resistance of the RE-Ni-Mo-P-B₄C-PTFE composite increase with increasing temperature, reaching peak values at 400°C and 300°C, respectively. The wear resistance of the composite coating is greatly superior to that of other traditional coatings.     

A novel load-insensitive Co3Mo2Si reinforced in-situ metal-matrix composite coating for wear resistance application

A novel Co₃Mo₂Si/Co_ss in-situ metal-matrix composite coating consisting of hard and strong intermetallic Co₃Mo₂Si and ductile Co solid solution was fabricated by a laser cladding process. The microstructure of the coating was characterized and the wear property was evaluated under dry sliding wear test conditions. Results indicated that the coating displayed very excellent wear resistance, and was extremely insensitive to the load.