高速电弧喷涂FeAlNbB非晶纳米晶涂层的组织与性能

为了提高钢铁材料的耐磨性和硬度,利用高速电弧喷涂技术在45钢基体上制备了FeAlNbB非晶纳米晶涂层.采用扫描电镜(SEM)、能谱分析仪(EDAX),透射电镜(TEM)和X射线衍射仪等设备对涂层的组织结构和相组成进行了分析,研究了非晶纳米晶的形成机制.实验结果表明:FeAlNbB非晶纳米晶涂层是非晶相、α-Fe、FeAl纳米晶和Fe3Al微晶共存的多相组织,涂层中非晶相含量约36.2%,纳米晶尺寸约14.1 nm;涂层组织均匀,结构致密,平均孔隙率约2.3%;非晶纳米晶涂层具有较高的硬度,其耐磨性是相同实验条件下制备的3Cr13涂层的2.2倍.     

Microstructure and mechanical characteristics of iron-based coating prepared by plasma transferred arc cladding process

This paper investigated the effect of electromagnetic stirring (EMS) on the microstructure and abrasive wear behavior of iron-based coatings. A series of coatings were prepared by using plasma transferred arc cladding (PTAC) process. The phase and structure of the coatings were characterized by means of SEM, EDXA and X-ray diffraction. The microstructure of the coatings was mainly γ-Fe matrix and (Cr, Fe)₇C₃ carbide reinforced phases. Without EMS, the average size of (Cr, Fe)₇C₃ carbide was about 73 μm, while that of the carbide reached a minimum value of about 20 μm with stirring current of 3 A. The mechanical properties, especially wear resistance, were analyzed in detail. The results showed that the microstructure of the coating plays an important role on abrasive mechanism and the main mechanism is micro-cutting. When the stirring current is 3 A, the coating exhibits excellent wear resistance, which contributes to the good microstructures that hexagonal (Cr, Fe)₇C₃ carbide with the highest volume fraction are uniformly distributed in the matrix. The microhardness of the coatings increase at first, and then decrease as a function of stirring current. The maximum microhardness value of the coating is about 1050 HV.     

Characteristics of Plasma-Sprayed Ceramic Coatings and Their Engineering Application

The microstructure, porosity, microhardness and adhesive strength of three plasma- sprayed ceramic coatings (Al2 O3, Cr2 O3 and Cr3 C2 NiCr) were tested. The wear resistance of the coatings was characterized through sand blasting test. The results showed that the erosion resistance of Cr2 O3 coating was better than Al2 O3 and Cr3 C2 NiCr coatings'.Through depositing the coating on the surface of boiler overheater tubes and on the surface of baffle- wall of carrying- coal grain blower to test its anti- erosion performance after a period of running, it was confirmed that the coatings present excellent wear resistance. Accordingly, it also demonstrates that ceramic coating has a promising prospects in surface protection in thermal power stations.     

CoCuFeNiTi高熵合金涂层的制备和性能研究

采用激光熔覆技术在40 Cr钢基材表面制备CoCuFeNiTi高熵合金涂层,使用SEM、XRD和EDS等手段分析涂层的显微组织和相组成,研究了涂层的制备工艺、显微硬度、耐磨损和耐腐蚀性能。结果表明：在激光功率为700 W、扫描速度为6 mm/s条件下制备的CoCuFeNiTi高熵合金涂层表面质量较好,涂层与基体之间形成了良好的冶金结合;这种涂层由FCC相、少量的Cu₄Ti相和微纳级富Cu析出相构成,具有典型的树枝晶显微组织,Cu元素在枝晶间偏聚并形成微纳级富Cu析出相;涂层的显微硬度约为438.83HV,是基体的1.7倍;涂层的磨损质量损失约为基体的1/2,表明这种涂层具有更高的耐磨损性能。涂层的磨损,以黏着磨损为主伴有一定程度的磨粒磨损;这种涂层在pH=4的酸性溶液和3.5%NaCl溶液中的耐蚀性均优于基体。     

超音速火焰喷涂WC-10Co-4Cr涂层的微观组织与摩擦磨损性能

采用超音速火焰(High Velocity Oxygen Fuel,HVOF)喷涂技术在Q235钢基体上制备WC-10Co-4Cr涂层。利用透射电子显微电镜、扫描电子显微电镜、X射线衍射仪、显微硬度计、摩擦磨损试验机等手段对涂层的微观组织结构和摩擦磨损性能进行研究。结果表明:采用HVOF喷涂技术制备的WC-10Co-4Cr涂层结构致密,与基体结合良好,孔隙率为0.67%。涂层中的物相以WC为主,此外还含有少量W2C相和非晶相。涂层的平均显微硬度为1230HV0.3。WC-10Co-4Cr涂层具有良好的耐摩擦磨损性能,累计磨损量(14.4mg)仅为Cr12MoV冷作模具钢的2/5。磨粒磨损为WC-10Co-4Cr涂层的主要磨损机制。     

Microstructure and mechanical properties of copper–titanium–nitrogen multiphase layers produced by a duplex treatment on C17200 copper–beryllium alloy

In this study, a copper–titanium–nitrogen multiphase coating was fabricated on the surface of C17200 copper–beryllium alloy by deposition and plasma nitriding in order to improve the surface mechanical properties. The phase composition, microstructure and microhardness profiles of the as-obtained multiphase coating were characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM) and Vickers microhardness measurements, respectively. Pin-on-disk tribometer and SEM equipped with energy dispersive spectrometer (EDS) were applied to measure tribological properties and analyze wear mechanisms involved. The XRD results show that the phase composition changes with nitriding temperature. The Ti₂N layer is replaced by a Cu–Ti intermetallic layer when the nitriding temperature is higher than 700 °C. The Cu/Ti ratio in the multiphase coatings remains at a constant value of 2:1 due to the incorporation of nitrogen atoms. The surface hardness achieves a maximum value of 983 HV at 650 °C, and decreases as the nitriding temperature increases. The increased hardness corresponds to the improved wear resistance and decreased frictional coefficient and the surface hardness is proportional to the wear rates. The wear mechanism depends on the phase composition of the multiphase coatings. With the nitriding temperature increasing, the oxidative wear mechanism changes to adhesive and abrasive mode.     

AC-HVAF非晶和金属陶瓷涂层在压裂液中空蚀行为研究

采用超声空蚀与电化学测试相结合的方法,对AC-HVAF热喷涂非晶金属和金属陶瓷两种涂层在水力压裂液中的空蚀及交互作用规律进行了研究,分析了耐蚀性和硬度在空蚀时的主导作用,确定了空蚀机理。结果表明,压裂液中KCl恶化了涂层的腐蚀性能,进而影响了空蚀行为。涂层在压裂液中的抗空蚀性能是耐蚀性与硬度结合的双变量函数。空化的力学破坏对高硬度涂层的空蚀过程有显著影响,硬度相对较高的金属陶瓷防护涂层的抗空蚀性能优异。压裂工况下,AC-HVAF涂层空蚀损伤是由于气泡溃灭垂直冲击孔隙或缺陷区域,硬相直接被剥离表面。降低孔隙和提高粘结相结合强度有助于提高涂层在压裂液中的抗空蚀性能。     

冷热循环处理对钛基非晶合金摩擦学性能的影响EI北大核心CSCD

钛合金的耐磨性较差,在钛合金活动部件表面制备钛基非晶合金涂层是一种保持钛合金优势又提升其耐磨性的选择。采用X射线衍射仪、差示扫描量热仪、SEM、摩擦磨损试验机,对冷热循环处理前后钛基块体非晶合金的组织结构与摩擦行为进行比较研究。结果表明:经过冷热循环处理后的钛基块体非晶合金仍然保持着完全非晶态,弛豫焓提升11%。冷热循环处理后钛基非晶合金的平均纳米硬度从6.84 GPa降低到6.59 GPa,平均弹性模量从118.70 GPa降低到103.43 GPa,但硬度与弹性模量的比值增大。冷热循环处理后,钛基块体非晶合金在5 N和10 N的载荷下磨损率减小了约10%。与TC4合金相比,其在5 N和10 N载荷下的磨损率分别减小了20%和50%。TC4合金由于硬度较低,呈现较为严重的黏着磨损。冷热循环处理后,钛基非晶合金的磨损机制从铸态的磨粒磨损为主向磨粒磨损、黏着磨损和氧化磨损共同作用转变,且随着载荷的增大,黏着磨损减轻,磨粒磨损占据主导。因此,冷热循环处理是提升钛基块体非晶合金摩擦学性能的一种有效方法。     

超音速火焰喷涂TiB2-50Co涂层及其性能

在322、402和462 L/min 3种氧气流量条件下采用超音速火焰喷涂技术制备了3种TiB₂-50Co涂层,通过SEM和XRD对涂层的微观组织和物相结构进行分析,测试其硬度,采用水淬法测试涂层的抗热震性能,并研究了涂层的耐熔融铝硅(Al-12.07wt%Si)合金腐蚀和耐磨粒磨损性能.研究结果表明:3种TiB₂-50Co涂层的物相均为TiB₂和Co;3种涂层的组织均致密,其中以氧气流量为322 L/min条件下制备的涂层试样最致密,其孔隙率最低(1.76%),涂层硬度值最高,达到(558±90) HV_0.3;氧气流量为462 L/min条件下制备的涂层抗热震性能最差,涂层截面出现明显裂纹;在熔融Al-12.07wt%Si合金中腐蚀60 h后,3种涂层均具有良好的耐熔融Al-12.07wt%Si腐蚀性能;在载荷为6 N的条件下,3种涂层均具有良好的耐磨损性能,以氧气流量为322 L/min条件下制备的涂层试样最佳.     

Wear behaviors of Fe-based amorphous composite coatings reinforced by Al2O3 particles in air and in NaCl solution

In this paper, the influence of the addition of Al₂O₃ particles on the microstructure and wear properties of Fe-based amorphous coatings prepared by high velocity oxygen fuel (HVOF) has been studied. The wear behaviors of the composite coatings were evaluated against Si₃N₄ in a pin-on-disk mode in air and in 3.5 wt.% NaCl solution. It was found that the Al₂O₃ particles were homogenously distributed in the amorphous matrix and the composite coatings exhibited improved wear resistance and reduced coefficient of friction (COF) in both air and wet conditions as compared to the monolithic amorphous coating. The composite coating reinforced with 20 wt.% Al₂O₃ particles exhibit the best wear performance, which, for example, has extremely low COF (< 0.2) and high wear resistance (2–3 times higher than monolithic amorphous coating). Detailed analysis on the worn surface indicated that the wear mechanism for the amorphous and composite coatings is similar and is dominated by oxidative delamination in air and by corrosion wear in 3.5% NaCl solution. The enhanced wear resistance is mainly attributed to the addition of Al₂O₃ particles which exhibit high hardness, good corrosion resistance and excellent chemical and thermal stability.     

反应等离子喷涂TiC/Fe涂层的摩擦磨损性能研究

采用等离子喷涂前驱体热分解技术制备的Fe-Ti-C系反应热喷涂粉末,在低碳钢基体上沉积TiC/Fe金属陶瓷复合涂层.利用SEM和X射线衍射仪对涂层的显微组织结构、磨损表面及其相组成进行分析;采用SRV型往复式摩擦磨损试验机评价喷涂涂层的摩擦磨损性能.结果表明: TiC理论含量为53%(质量分数)TiC/Fe金属陶瓷涂层的耐磨粒磨损性能较好,相比基体提高了约25倍;反应等离子喷涂TiC/Fe陶瓷涂层的磨损机制主要为粘着磨损和轻微的剥落.     

等离子熔覆ZrB_2-ZrC/Fe复合涂层组织及耐磨性

采用等离子熔覆技术,以Zr、Fe、B_4C混合粉末为原料,在Q235低碳钢表面原位反应合成了ZrB_2和ZrC增强的Fe基复合涂层,分析了ZrB_2-ZrC/Fe涂层的物相组成和组织结构,并进行了硬度、耐磨性对比试验,探讨了物相和组织结构的形成过程及磨损机制。结果表明:涂层主要物相为ZrB_2、α-Fe、ZrC、Fe_2B和Fe_3C,其中ZrB_2呈现针棒状、花瓣状,ZrC呈现规则的颗粒状;随着原始粉末中(Zr+B_4C)含量的增加,增强相ZrB_2和ZrC含量增多,尺寸变大,ZrB_2-ZrC/Fe涂层与Q235钢基体之间结合紧密,呈冶金结合;与Q235钢基体相比,ZrB_2-ZrC/Fe涂层耐磨性显著提高,最高可达基体的5.45倍,ZrB_2-ZrC/Fe涂层的磨损方式以磨粒磨损为主,断裂方式以穿晶断裂为主。     

Effects of Cr contents in Fe-based bulk metallic glasses on the glass forming ability and the corrosion resistance

Fe-based bulk metallic glasses of Fe_69.9?xC_7.1Si_3.3B_5.5P_8.7Cr_xMo_2.5Al_2.0Co_1.0 (x = 0.0, 2.3–12.3) with high glass forming ability and good corrosion resistance were fabricated using industrial raw materials. Glass forming ability of the Fe-based bulk metallic glasses tends to decrease with the Cr content, while the corrosion resistance increases with the Cr content. A homogeneous passive layer on the amorphous sample with 12.3 at% Cr can be formed leading to superior corrosion resistance of the amorphous sample to an austenitic stainless steel (SUS304) in the 0.5 M H₂SO₄ and 1N HCl solutions at 298 K. Fe-based bulk metallic glasses with an optimum combination of glass forming ability and corrosion resistance can be produced in large quantities through a systematic control of the Cr content for extensive practical applications.     

超声辅助激光熔覆IN 625高温合金涂层组织及性能研究

目的 针对激光熔覆制备IN625高温合金涂层时易产生缺陷和元素偏析进而导致合金性能下降的问题,提高增材制造IN 625高温合金的力学性能。方法 在激光熔覆IN 625涂层的过程中施加超声振动辅助,通过物相检测和微观组织观测研究超声功率对涂层物相种类和晶体尺寸的影响;通过分析析出相含量、分布方式及析出形态,研究超声功率对元素偏析的影响;通过对显微硬度、高温耐磨性进行测试,研究超声功率对涂层力学性能的影响。结果 施加超声前的涂层组织主要为方向杂乱的粗大枝晶,施加超声后的涂层物相组成未发生明显变化,但枝晶内亚晶排列紧密且尺寸明显减小;施加超声振动后的涂层析出相尺寸减小、含量下降,其中Laves相含量在施加超声后降幅较大,表明超声振动可以抑制Nb、Mo等元素的偏析;施加超声振动后涂层的显微硬度提高,磨损率明显下降,磨损机制由原来的表面疲劳磨损、黏着磨损和磨粒磨损的复杂磨损转变为磨粒磨损、黏着磨损的简单磨损。结论 施加超声辅助可以有效细化IN 625涂层组织,并抑制Laves相的析出,提高涂层的硬度和耐磨性。     

Feasibility study on preparation of coatings on Ti–6Al–4V by combined ultrasonic impact treatment and electrospark deposition

A novel method combining ultrasonic impact treatment (UIT) with electrospark deposition was developed to prepare coatings on Ti–6Al–4V substrates. The microstructure, phase composition, residual stress, microhardness, and wear performance of the coating were studied, and new amorphous and nanocrystalline phases (titanium carbide nitride and iron titanium oxide) were found. In addition, the residual stress in the coating and in the substrate near the coating is compressive stress. The maximum compressive residual stress is about −717 MPa, and its depth is about 470 μm. Because of contributions from multiple factors, the wear volume loss of the sample subjected to combined UIT and electrospark processing was reduced by four orders of magnitude compared with that of the base material.     

Microstructure and properties of in situ nanostructured ceramic matrix composite coating prepared by plasma spraying

In situ nanostructured ceramic matrix composite coating toughened by metallic phase was fabricated by reactive plasma spraying micro-sized Al–Fe₂O₃ composite powders. The microstructure of the composite coating was characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy, respectively. The adhesive strength, microhardness, toughness, and wear resistance of the composite coating were explored. The results indicated that the composite coating exhibited dense microstructure with a lot of spherical α-Fe and γ-Al₂O₃ nano-sized grains embedded within the equiaxed and columnar FeAl₂O₄ nano-grains matrix. The adhesive strength, toughness, and wear resistance of the composite coating were significantly enhanced despite its lower microhardness compared with the micro-sized Al₂O₃ coating, which were attributed to the inclusion of ductile metallic phase Fe in the composite coating and the nanostructure of the composite coating.     

Enhancement of oxidation and wear resistance of Fe-based amorphous coatings by surface modification of feedstock powders

Surface oxidation of the in-flight powders during the preparation of amorphous coatings in high velocity oxygen fuel process causes the formation of oxygen-rich intersplat regions. These regions are brittle in nature and can dramatically deteriorate the mechanical performance of the coatings. To solve this problem, the starting FeCrMoCBY amorphous feedstock powders were modified by electroless plating a thin layer of Ni–W–P amorphous phase. It was found that the covering of the Ni–W–P layer can significantly reduce the oxygen content in the resultant Fe-based amorphous coatings. The wear resistance of the coatings with and without the modification of Ni–W–P thin layer was comparatively studied by ball-on-disk wear tests against Si₃N₄ counterpart in air. It revealed that the wear of two types of coatings follows the same oxidation wear mechanism but the modified coating exhibits much better wear resistance due to the improved oxidation resistance.     

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.     

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.     

High-velocity oxygen-fuel spray parameter optimization of nanostructured WC–10Co–4Cr coatings and sliding wear behavior of the optimized coating

In this paper, the Taguchi method was employed to optimize the spray parameters (spray distance, oxygen flow and kerosene flow) to achieve the highest hardness and, in turn, the best wear resistance of the high-velocity oxygen-fuel (HVOF) sprayed nanostructured WC–10Co–4Cr coating by investigating the correlation between the spray parameters and the hardness. The important sequence of spray parameters on the hardness of the coatings is kerosene flow > oxygen flow > spray distance, and the kerosene flow is the only significant factor. The optimal spray parameter (OSP) for the coating is obtained by optimizing hardness (330 mm for the spray distance, 2000 scfh for the oxygen flow and 6.0 gph for the kerosene flow). The coating deposited under the OSP with low porosity and high microhardness consists predominately of WC and a certain amount of W₂C phases. The coating deposited under the OSP exhibits better wear resistance compared with the cold work die steel Cr12MoV. The material removal of the coating is the extrusion of the ductile Co–Cr matrix followed by the crack and the removal of the hard WC particles.