AISI1045钢表面激光熔覆FeCoCrNiAl0.5Ti0.5涂层的界面特性及摩擦性能

激光熔覆高熵合金涂层摩擦磨损行为的研究主要聚焦在涂层表面,鲜有对熔覆层/基体界面区域的摩擦学行为进行研究。为了提高AISI 1045钢的耐磨性,采用激光熔覆技术在AISI 1045钢基体表面制备宏观形貌良好、组织均匀的FeCoCrNiAl_0.5Ti_0.5高熵合金涂层。利用OM、XRD、SEM、EDS和摩擦磨损测试仪对激光熔覆FeCoCrNiAl_0.5Ti_0.5涂层的微观结构、物相组成、界面特性和摩擦磨损性能进行研究。通过对FeCoCrNiAl_0.5Ti_0.5涂层XRD图谱和元素分布分析发现,涂层主要由面心立方(Fe,Ni)相和体心立方相(BCC)形成的共晶组织及其中弥散分布着的Ni Al金属间化合物构成。硬度测试表明,从涂层顶部到基体,涂层、稀释区、热影响区和基体的平均显微硬度分别为518±20、561±63、473±81和217±12 HV0.2。涂层/基体界面区域生成了Cr₂₃C₆,在摩擦过程中会形成一层摩擦...     

Fabrication and microstructure of Fe-based amorphous composite coatings by laser cladding

Fe-based amorphous composite coatings were fabricated on AISI 1045 steel by laser cladding. The results of the X-ray diffraction and transmission electron microscopy analyses show the coating is composed of an amorphous phase in majority and a nanocrystalline phase in minority. Phase composition of the coating changes along the depth of the coating. The reasonable scanning speed for fabricating an amorphous composite coating is 3 500mm/min when the laser power is 4 800W and the laser beam diameter is 2mm. If the scanning speed is lower than 3 500mm/min, the intensity of the two main diffraction peaks in X-ray diffraction patterns of the coatings decreases with the scanning speeds increasing. At the same time, a broad halo peak emerges and enlarges. High laser power and fast scanning speed are the essential conditions of amorphization. The coating exhibits high microhardness.     

激光重熔对电弧喷涂含非晶相铁基涂层性能的影响

目的提高电弧喷涂含非晶相Fe基涂层的抗冲蚀及耐腐蚀性能。方法采用YAG脉冲激光器对电弧喷涂含非晶相Fe基涂层进行激光重熔处理。通过X-ray、SEM、冲蚀磨损和电化学等检测手段,研究该涂层重熔后的组织结构、冲蚀磨损性能和耐腐蚀性能。结果电弧喷涂含非晶相Fe基涂层经激光重熔后发生了晶化,并随着功率的增加,非晶含量降低,硬度也降低。重熔后,涂层与基体的结合方式由之前的机械咬合转变为冶金结合,涂层的致密度明显提高,组织缺陷减少。与喷涂层相比,0.3k W激光重熔涂层的抗冲蚀性能在30°攻角下可提高3倍,在90°攻角下可提高将近6倍。重熔层的冲蚀磨损机制在低冲角时以显微切削为主,高冲角时则以挤压破碎为主。随着激光功率的增加,重熔涂层的抗冲蚀性能降低。同时,在3.5%NaCl溶液中,重熔层的耐蚀性能随重熔激光功率的提高而提高,并且重熔层的腐蚀电流密度比喷涂层明显降低。结论激光重熔不但改善了电弧喷涂含非晶相Fe基涂层与基体间的结合状态,同时也增强了涂层的耐蚀和耐磨性能,是一种有效提升涂层性能的后处理工艺。     

Optimum Me-DLC coatings and hard coatings for tribological performance

In this study, hard coatings (TiN, TiCN, CrN, and CrCN) and Me-DLC coatings (Ti _x%-C:H and Cr _x%-C:H) were deposited on tungsten carbide (WC) substrate by multiarc physical vapor deposition (MAPVD) and unbalanced magnetron (UBM) sputtering, respectively. Counterbodies of the AISI 1045 steel cylinder and the AA7075T651 aluminum cylinder were used in the cylinder-on-disk, line-contact wear mode under dry condition; a counterbody of the AISI 52100 steel ball was used in the ball-on-disk, point-contact wear mode, under both dry and lubricated conditions. All wear tests were conducted with a reciprocating machine. After the tests, the most suitable coating for various counterbodies and test environments was selected. For the coating/1045 steel cylinder, the Ti_10%-C:H coating possesses excellent tribological characteristics. For the coating/7075T651 aluminum cylinder, hard coatings display excellent wear resistance. For the coating/steel ball, CrCN and CrN coatings display very little wear under both dry and lubricated conditions. On TiN and TiCN coatings, special wear mechanisms of material transfer, adhesion wear, and fatigue fracture occurred during initial tests under kerosene lubrication.     

Synthesis and Erosion Behaviors of Nanoscale Coatings Prepared by Wire Arc Spraying

The effects of erosive parameters,such as impact angles and environment temperature,on erosion properties of FeBSiCrMnNb nanoscale coatings were investigated.A series of coatings were prepared by wire arc spraying process.The microstructure of the coating consists of amorphous andα(Fe,Cr)nanocrystalline phase.The nanocrystals with average size of 39 nm are homogenously dispersed in amorphous matrix.The erosion results reveal that the coating exhibits better erosion resistance at lower impact angle.The erosion rates of the coating decrease as function of environment temperature.The relatively erosion resistance of the nanoscale coating is 3.7 times higher than that of AISI1045 steel substrate at 650°C.The main failure mechanism of the coating is brittle fracture.     

Effect of h-BN addition on the properties of nanostructured Al2O3-TiB2-TiN based coatings developed by combined SHS and laser surface alloying

A hard coating was obtained on AISI1025 steel substrate by the action of a high power laser beam on a powder mixture of Al, TiO₂ and h-BN pre-placed on the substrate surface. The precursor powder mixture underwent self-propagating high-temperature synthesis (SHS) at the high temperatures induced by the incident laser. The products of SHS were subsequently laser alloyed onto the substrate, whereby, a hard, nanostructured coating was formed comprising of Al₂O₃, TiB₂ and TiN. Excess h-BN in the precursor resulted in the presence of free h-BN in the coating. Microhardness and coefficient of friction (with WC-Co as counterbody) of the coating were found to reduce with increase in h-BN content in the precursor. It was possible to develop a coating with a property combination of high hardness, low wear rate and low friction coefficient.     

Effect of Niobium on the Microstructure and Wear Resistance of Nickel-Based Alloy Coating by Laser Cladding

The nickel-based alloys with different Nb contents were deposited on AISI 1045 carbon steel by laser cladding. The effect of Nb on the microstructures of the nickel-based alloy coatings was investigated using scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The result show that the microstructures of the Nb-modified nickel-based alloy coatings are mainly composed of γ-Ni dendrites, interdendritic eutectics, CrB type chromium borides, and dispersed NbC particles. It is found that the addition of Nb will lead to the precipitation of the NbC particles and M23C6 type carbides instead of the M7C3, and M23C6 type carbides can be observed in the Nb-free nickel-based alloy coating. The microhardness and wear resistance of the coatings increase with the increase of Nb contents. The improvement of the wear resistance of the Nb-modified nickel-based alloy coatings is attributed to the microstructural change and phase variation.     

沉积气氛对电火花沉积Mo2FeB2基金属陶瓷涂层组织与性能的影响

采用电火花沉积分别在空气和氩气中制备了Mo_2FeB_2基金属陶瓷涂层,通过扫描电镜(SEM)、X射线衍射(XRD)、显微硬度计和摩擦磨损试验机研究了沉积气氛对涂层形貌、相组成、硬度和摩擦磨损性能的影响。结果表明,2种气氛中沉积所得涂层的组织结构都致密,涂层与基体间无分层,呈冶金结合的特征,但空气中沉积涂层的表面较粗糙,并发生了严重的氧化,涂层均匀性也较差。它们都主要由非晶相和马氏体相组成,但氩气中沉积的涂层含有更多的非晶相。氩气和空气中沉积涂层的最大显微硬度(HV_(0.05))分别为12 862和10 129 MPa,相差2733 MPa,前者涂层2 h的磨损量几乎仅为后者涂层的1/7,表现出更好的耐磨性。2种涂层的主要磨损机制都是疲劳磨损和磨粒磨损,但氩气中沉积涂层以疲劳磨损为主,空气中沉积涂层则以磨粒磨损为主。     

Study on the effect of laser post-treatment on the properties of nanostructured Al2O3-TiB2-TiN based coatings developed by combined SHS and laser surface alloying

A nanostructured, hard and wear resistant composite coating of Al2O3, TiB2 and TiN isformed on low carbon steel (AISI 1025) substrate by combined self-propagating high-temperaturesynthesis (SHS) and laser surface alloying (LSA). A precursor powder mixture of Al, TiO2 and hBNpreplaced on the substrate surface undergoes self-propagating high-temperature synthesis (SHS) atthe high temperatures induced by the incidence of laser. The products of SHS are subsequently laseralloyed onto the substrate to form the coating. The high power laser beam is again made to pass overthe coating with a view to remelt the coating top layer. This laser post-treatment causes distinct enhancements in microhardness and tribological performance by the modification of themicrostructure of top portion of the coating.     

Wear behaviour of steel coatings produced by friction surfacing

Friction surfacing was performed to produce multi-layer coatings of AISI 1024, AISI 1045 and AISI H13 over mild steel substrates where a continuous joining was achieved between adjacent layers and between the clad and the substrate. Microscopic and hardness characterization revealed the presence of bainitic and martensitic microstructures which influenced the hardness of the coatings. The study aimed to determine which material combination was more wear-resistant. The analysis suggested that AISI 1024 presents the least wear, both in terms of friction coefficient and wear rate. This is due to the formation of adherent protective oxide layer which is not present in both the AISI 1045 and AISI H13 steels.     

Experimental Study of the Microstructure and Micromechanical Properties of Laser Cladded Ni-based Amorphous Composite Coatings

(Ni_0.6Fe_0.4)₆₅B₁₈Si₁₀Nb₄C₃ amorphous composite coating was successfully fabricated on AISI 1045 steel substrate by using laser cladding process with coaxial powder feeding equipment. The microstructure and phase distribution of the coating were investigated by using x-ray diffraction, scanning electron microscopy and transmission electron microscope. The mechanical properties of the coating were examined by using microhardness testing and nanoindentation. The experimental results indicated that the volume fraction of amorphous phase increased with the decrease in laser cladding heat input, leading to an improvement of mean microhardness and nanohardness. NbC particles in a size ranging between 150 and 1650 nm were found embedding in the amorphous composite coatings in all situations. The presence of the NbC particles can contribute to an improvement of 96.7 HV in hardness on the basis of experimental results, while theoretical prediction suggests an improvement of 92.5 HV by using Orowan-Ashby equation.     

等离子喷涂硫化亚铁润滑层的摩擦学性能

利用等离子喷涂在 45钢表面制备了三种厚度不同的硫化亚铁固体润滑层。在QP 1 0 0摩擦磨损试验机上测定了硫化亚铁喷涂层在油润滑条件下的摩擦学性能。利用XRD分析了硫化亚铁喷涂层的相结构 ,用SEM观察了喷涂层的磨面形貌。结果表明 ,硫化亚铁喷涂层的减摩、耐磨、抗擦伤性能明显优于 45钢原始表面。     

Microstructure and Corrosion Resistance of Fe-Based Coatings Prepared by Twin Wires Arc Spraying Process

FeB, FeBSi, and FeNiCrBSiNbW coatings were prepared by twin wires arc spraying process on AISI 1045 steel substrate, and the microstructure and phases were characterized by scanning electron microscope, transmission electron microscope, and x-ray diffraction. The corrosion resistance was investigated by means of electrochemical tests. It was found that FeB coating and FeBSi coating were composed of α-Fe, FeO, and Fe₂O₃ phases. FeNiCrBSiNbW coating consisted of amorphous phase and α-(Fe, Cr) nanocrystalline phase, with porosity of 1.8%, hardness of 807 Hv_0.1 and tensile bonding strength of 52.1 MPa. Three kinds of electrochemical tests were employed to identify the corrosion resistance of the coatings. The results indicated that the FeNiCrBSiNbW coating had a superior corrosion resistance, much better than FeB and FeBSi coatings. It was attributed to the amorphous/nanocrystalline structure and the presence of corrosion-resistant element Cr.     

激光熔覆FeCoCrxNiB高熵合金涂层的组织结构与耐磨性

为探究Cr元素对高熵合金涂层组织结构和性能的影响,在45钢基体上用激光熔覆方法制备了FeCoCrxNiB高熵合金涂层,采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、显微硬度和耐磨测试等方法研究了Cr含量对FeCoCrxNiB激光熔覆高熵合金涂层组织结构、硬度和耐磨性能的影响。结果表明:熔覆态高熵合金的组织均由先共晶M2B相和共晶组织(面心立方结构相(FCC)+M2B相)组成。随着Cr含量的增加,共晶组织含量增多,M2B相减少,先共晶硼化物形态呈现不规则颗粒状到树枝状再到条块状的变化,共晶组织形貌由蜂窝状向片层状转变。涂层平均硬度随着Cr含量增加逐渐降低,FeCoCr0.5NiB涂层平均硬度最高为860HV0.2。涂层的耐磨性能与硬度呈正相关关系,即FeCoCr0.5NiB涂层耐磨性最高,FeCoCr3NiB涂层耐磨性最低。     

激光熔覆超音速火焰喷涂陶瓷复合涂层的结构和性能

对YAG激光器产生的矩形激光束及在熔覆超音速火焰喷涂陶瓷复合涂层过程中激光功率对涂层组织和性能的影响进行了研究.采用扫描电镜分析了激光熔覆后的涂层组织结构,比较了采用不同激光输出功率2、3、4kW所得熔覆层的显微硬度和耐磨性能.结果表明:激光熔覆层与基体为冶金结合,熔覆层的硬度较喷涂层的硬度有所提高,并随着激光功率的提高而增加.激光熔覆层的磨损失重远低于喷涂层.     

铝硅合金表面激光Cr／WC梯度层组织及抗微动磨损性能研究

利用5kWCO2激光器对铸造铝硅合金表面进行两次激光辐照,先后将不同成分的预置合金粉末和基体材料一起熔化后迅速凝固,在其表面获得Cr/WC激光表面梯度层,并对它们的显微组织进行分析,发现在表面梯度层中存在大量的Al/Cr化合物Al9Cr4。在激光表面梯度层中自表及里显微硬度基本呈连续变化趋势,而单次激光表面合金化层与基体之间的显微硬度值有一突变,在基体和激光表面改性层的微动磨损试验中发现,激光改性后的表面抗微动磨损的能力增强,磨损机制不同于铝硅合金基体,而表现出较好的抗粘着损伤性能。     

电火花沉积Invar/非晶复合涂层的组织与性能

采用电火花沉积技术在45Mn2钢基材表面沉积了Invar、Invar/非晶及Invar/非晶/Invar涂层,通过X射线衍射仪(XRD)、扫描电镜(SEM)、摩擦磨损试验仪和电化学工作站等分析了沉积层的组织结构、摩擦磨损和电化学腐蚀性能。结果表明,制备的涂层致密、均匀,与基材呈冶金结合。采用Invar合金打底,获得了约60 μm厚度的无显著裂纹Invar/非晶/Invar涂层。Invar涂层为FCC固溶体结构,Invar/非晶和Invar/非晶/Invar涂层为非晶/固溶体复相结构。Invar、Invar/非晶和Invar/非晶/Invar沉积层的平均硬度分别为176.6、 757.7和772.8 HV0.1,摩擦因数分别为0.44、0.21和0.19。提高沉积层非晶含量可提高硬度,降低摩擦因数,提高耐磨性。沉积层在3.5%NaCl溶液中没有明显的钝化现象,Invar、Invar/非晶及Invar/非晶/Invar涂层的自腐蚀电位分别为-0.74、 -0.54、-0.34和-0.31 V,自腐蚀电流密度分别为7.08、5.15、3.78和3.11 μA·cm^-2。电火花沉积的Invar/非晶/Invar涂层致密、均匀、无裂纹,可极大提高45Mn2钢基体表面的耐磨及耐蚀性能。     

Studies on the Sliding Wear Performance of Plasma Spray Ni-20Cr and Ni3Al Coatings

Two metallic powders namely Ni-20Cr and Ni₃Al were coated on AISI 309 SS steel by shrouded plasma spray process. The wear behavior of the bare, Ni-20Cr and Ni₃Al-coated AISI 309 SS steel was investigated according to ASTM Standard G99-03 on a Pin-on-Disc Wear Test Rig. The wear tests were carried out at normal loads of 30 and 50 N with a sliding velocity of 1 m/s. Cumulative wear rate and coefficient of friction (μ) were calculated for all the cases. The worn-out surfaces were then examined by scanning electron microscopy analysis. Both the as-sprayed coatings exhibited typical splat morphology. The XRD analysis indicated the formation of Ni phase for the Ni-20Cr coating and Ni₃Al phase for the Ni₃Al coating. It has been concluded that the plasma-sprayed Ni-20Cr and Ni₃Al coatings can be useful to reduce the wear rate of AISI 309 SS steel. The coatings were found to be adherent to the substrate steel during the wear tests. The plasma-sprayed Ni₃Al coating has been recommended as a better choice to reduce the wear of AISI 309 SS steel, in comparison with the Ni-20Cr coating.     

Preparation and characterization of graphite-nickel composite coatings by automatic brush plating

Composite coatings of nickel with G particles were produced on AISI 1045 carbon steel substrate by using a newly developed automatic brush plating system. Pure nickel coating was also prepared for comparative study. The volume percent incorporation of G powder in the composite coatings was investigated with respect to its concentration in bath and relative anode to cathode speed. It was shown that the volume percentage of G was strongly affected by these parameters. The G particle distribution in the composite coatings was uniform across the coating at low concentration of G in bath and agglomerated on the surface at high concentrations. The wear and friction properties of G-Ni composite coatings containing different amounts of G particles were studied. The results revealed that hardness, wear resistance and friction coefficient are dependent on volume percentage of G in composite coating. In this study, it was shown that G-Ni composite coating with 15% G possessed the best wear-resistance property.     

Mechanism of Zr in in situ-synthesized particle reinforced composite coatings by laser cladding

By adding mixture of ZrO_2 and carbon, a Zrenhanced composite coating was produced onto an AISI1045 substrate by laser cladding. The microstructure and phase formation, microhardness and wear resistance of the composite coating were studied. The experimental results indicate that the composite coating with metallurgical bonding to substrate consists of y-Ni, massive ceramic particles of ZrC,NiZr_2, Ni_7 Zr_2,(Fe,Ni)_(23)C_6 and Fe_3 C. The in situ-synthesized ZrC particles are uniformly dispersed in composite coating, which refines the microstructure of composite coating. With different Zr02 and carbon additions, the properties are improved differently. Finally, the fine in situ ZrC particles improve the microhardness of composite coating to HV_(0.2) 650, which is nearly 2.7 times that of Ni25 coating. Also, the composite coating has an advantage in wear resistance; it offers better wear resistance when more mixture of ZrO_2 and carbon was added in nickel alloys.