Influence of Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Particle Size on Microstructure,Mechanical Properties and Abrasive Wear Behavior of Flame-Sprayed and Remelted NiCrBSi Coatings

The influence of micrometric alumina (low surface area-to-volume ratio) and nanometric alumina (high surface area-to-volume ratio) on microstructure, hardness and abrasive wear of a NiCrBSi hardfacing alloy coating applied to an AISI 304 substrate using flame spraying (FS) combined with surface flame melting (SFM) is studied. Remelting after spraying improved the mechanical and tribological properties of the coatings. Microstructural characterization using XRD, SEM and EDS indicated that alumina additions produced similar phases (NiSi, Ni₃B, CrC and Ni₃₁Si₁₂) regardless of the alumina size, but the phases differed in morphology, size distribution and relative proportions from one coating to another. The addition of 12 wt.% nanometric Al₂O₃ increased the phases concentration more than five- to sixfold and reduced the hard phases size about four-to threefold compared with NiCrBSi + 12 wt.% micrometric Al₂O₃. Nanoalumina led to reduced mass loss during abrasive wear compared to micrometric alumina and greater improvement in hardness.     

氮合金化堆焊硬面合金组织与耐高温磨损性能

对马氏体不锈钢堆焊硬而合金进行了氮合金化,研究了其组织和耐高温磨损性能.结果表明,氮合金化马氏体不锈钢堆焊层显微组织主要为马氏体和铌、钛的复合碳氮化物;堆焊马氏体不锈钢硬面合金与碳钢的高温金属间磨损,为碳钢表面高温下形成的氧化皮,粘着于堆焊马氏体不锈钢硬面合金表面,导致堆焊马氏体不锈钢硬面合金产生磨粒磨损.氮合金化堆焊...     

激光熔覆NiCrBSi/Ag复合涂层 结构及空间摩擦学性能

目的 提高钛及钛合金的空间摩擦学性能,拓展钛及钛合金在空间技术领域的应用范围。方法 用激光熔覆技术在纯钛基材表面制备了NiCrBSi/Ag复合涂层。用X-射线衍射仪、扫描电镜和高分辨透射电镜分析涂层的物相组成、显微组织结构和晶体结构。用空间摩擦学实验系统对NiCrBSi/Ag复合涂层在真空、原子氧和紫外辐照三种模拟空间环境以及大气环境下的摩擦学性能进行系统的研究。采用扫描电镜和能量色散光谱仪对摩擦测试后NiCrBSi/Ag复合涂层的磨痕形貌和对偶不锈钢钢球的磨痕形貌及元素面分布进行分析。深入探讨NiCrBSi/Ag复合涂层在三种模拟空间环境及大气环境下的磨损机理。结果 在纯钛基材表面通过激光熔覆制备的NiCrBSi/Ag复合涂层主要物相组成为NiTi、Ni3Ti、Cr2Ni3、Cr3Si、TiB2、Cr-Ni-Ti-Fe、Ag相,显微结构主要为等轴晶和枝状晶组织。复合涂层具有较高的显微硬度,涂层截面平均显微硬度约为830HV0.2,约是钛基材硬度的4.4倍。复合涂层在真空、原子氧和紫外辐照模拟空间环境下的摩擦系数和磨损率均小于大气环境下的值。在三种模拟空间环境下,相对于纯钛基材,复合涂层的磨损率约小2个数量级。复合涂层在真空、原子氧和紫外辐照模拟空间环境下的磨损机理为粘着磨损和磨粒磨损,在大气环境下的磨损机理主要为磨粒磨损。结论 NiCrBSi/Ag复合涂层可以显著提高纯钛基材在真空、原子氧和紫外辐照三种模拟空间环境以及大气环境下的摩擦学性能。     

纳米WC增强Ni基合金喷熔层组织结构与抗磨粒磨损特性

目的研究纳米WC对Ni基合金喷熔层抗磨粒磨损性能的影响。方法采用扫描电镜、X射线衍射分析了氧乙炔火焰喷熔Ni基合金层和两种不同结构WC增强Ni基合金喷熔层的微观组织和相结构,并通过磨粒磨损试验平台对三种涂层进行磨损性能测试。结果纳米WC粉末的加入,能有效提高喷熔层的宏观硬度。通过组织分析得出纳米WC增强Ni基喷熔层中除含有γ-(Ni,Cr)固溶体、Cr的碳化物、硼化物以及微米级WC颗粒之外,还含有一定量的纳米WC团聚体和少量高硬度的W_2C相。磨粒磨损实验结果显示,纳米WC增强Ni基喷熔层的磨损失重分别为Ni60和NiWC35涂层失重的56%和73%。对比磨损后涂层的表面微观形貌可知,纳米WC颗粒在涂层中能有效降低磨粒压入喷熔层的深度,从而控制磨粒对喷熔层的犁削量。结论纳米WC增强Ni基合金喷熔层中含有的γ-(Cr,Ni)固溶体、Cr_(23)C_6、Cr_7C_3、Cr_3Ni_2及未熔化的WC颗粒和WC脱碳形成的W_2C等硬质相,使镍基自熔合金涂层的硬度有较大提高,同时也大大提高了涂层的抗磨粒磨损性能。     

纳米金刚石粒径对Ni-P化学复合镀层耐磨性和耐腐蚀性的影响

为提高化学镀镀层的耐磨性和耐腐蚀性,采用化学镀制备含不同粒径的纳米金刚石Ni-P-D复合镀层,通过SEM、XRD、摩擦磨损试验、磨粒磨损试验和电化学试验,探究纳米金刚石粒径对Ni-P镀层微观形貌、力学性能、摩擦磨损性能、磨粒磨损性能和耐腐蚀性能的影响。经化学复合镀可以得到与基体结合良好,厚度约为30 μm,含纳米金刚石的Ni-P-D复合镀层;含50 nm 金刚石的Ni-P-D复合镀层的硬度最高,抗摩擦磨损和磨粒磨损性能最好;随着纳米金刚石粒径减小,Ni-P-D复合镀层的摩擦系数和抗腐蚀能力提高,含5 nm金刚石的Ni-P-D复合镀层的摩擦系数最小,抗腐蚀能力最强。      

等离子弧堆焊铁基熔覆层组织结构与磨损行为

设计开发了一种铁基(含Cr,Mo,C,B,Si,Mn等元素)多元合金粉末,采用等离子弧堆焊(PTAW)技术在AISI304L不锈钢表面制备相应熔覆层,通过XRD,SEM,EDS及磨粒磨损试验机等对熔覆层微观组织结构和磨损行为等进行表征,并与传统NiCrBSi和NiCrBSi+25%WC粉末的PTAW熔覆层进行了对比研究.结果表明,所设计的铁基合金熔覆层成形良好,基体组织由Fe-Cr固溶体相与γ-Fe相构成,其间包裹着大量弥散分布的富钼硼化物和M₂₃(B,C)₆硬质相,对熔覆层组织能够起到有效的支撑和强化作用.铁基熔覆层的宏观硬度平均值高达64.2HRC,其相对耐磨性明显优于NiCrBSi+25%WC熔覆层,并达到NiCrBSi熔覆层的8倍以上.     

Improvement in high stress abrasive wear property of steel by hardfacing

High stress abrasive wear behavior of mild steel, medium carbon steel, and hardfacing alloy has been studied to ascertain the extent of improvement in the wear properties after hardfacing of steel. High stress abrasive wear tests were carried out by sliding the specimen against the abrasive media consisting of silicon carbide particles, rigidly bonded on paper base and mounted on disk. Maximum wear was found in the case of mild steel followed by a medium carbon alloy steel and a hardfacing alloy. Different compositions of steels and constituent phases present led to different wear rates of the specimen. The extent of improvement in wear performance of steel due to hardfacing is quite appreciable (twice compared to mild steel). Microstructural examination of the wear surface has been carried out to understand the wear mechanism.     

Dry coatings and ecodesign: Part. 2 — Tribological performances

The goal of this study is to find an industrial alternative application to hard chromium plating. The first part presents the appropriate environmental and chemical behaviour of NiCrBSi alloy and AISI 316L stainless steel coated by thermal spraying and laser cladding. This paper will concern the wear resistance of these dry coatings. However, stainless steel has awful performance in friction contacts, and this material cannot be suggested as a substitute solution to hard chromium coating for applications where the wear resistance is an important issue. Therefore the tribological pin-on-disc tests will only concern the NiCrBSi coatings. Consequently in the second part, tribological characterizations were carried out in order to determine the alternative potential of NiCrBSi coatings compared to electrolytic hard chromium plating, in applications to resist wear. The coatings are sprayed by Atmospheric Plasma Spraying (APS) and laser cladding (with a diode laser). Especially, the dry coated samples present a good tribological behaviour, whereas the wear mechanisms are different between APS and laser cladding coated samples. Laser cladding allows the manufacture of denser coatings, thus the mechanical properties are increased while the wear rate was reduced. At the same time, APS coated samples show a lower value of shear strength in comparison with laser cladding. That is the reason why fatigue is the main wear mechanism, and this process is called splat delamination.     

Study of the welding procedure in nanostructured super-hard Fe- (Cr,Mo, W) - (C,B) hardfacing

The optimization of the tribological properties of the surfaces by means of hardfacing techniques has made great progress in the metallurgical field in recent times. Alloys of the Fe-Cr-C and Fe-C-B type present excellent wear performance under severe conditions, where the incorporation of Nb, Mo and W improves the performance of severe abrasive wear. In this context, new semi-automatic welding consumables have been designed that deposit iron base material of high alloy, with complex carboborides of W, Mo and Cr which present very high hardness and resistant to abrasive wear. The purpose of this work was to compare microstructural variations coupons welded with one or two layers, with or without shielding gas. The chemical composition was measured on each coupon, the microstructure was characterized by X-ray diffraction and scanning electron microscopy. Dilution percentage was determined and Vickers microhardness profiles (HV2) were made on the different phases (HV_0.025). It was found that the dilution with and without shielding gas were 26% and 19%. The hardness was 960 and 1100 HV2. An increase in hardness was observed in the recrystallized areas, as well as a higher percentage of carboborides in the last bead.     

1Cr13NbTi不锈钢堆焊材料氮合金化分析

用氮代替部分碳,通过铌、钛固氮形成氮合金化1Cr13NbTi堆焊合金,深入分析了碳氮化物的形成机理,进行了耐磨粒磨损性能试验,研究了碳氮化物对堆焊合金耐磨粒磨损行为的影响.结果表明,堆焊合金中的碳氮化物为分布在晶界和晶内的MX（M=Nb,Ti;X=C,N）复合型碳氮化物.焊态和热处理条件下具有不同的数量和尺寸,初生的碳氮化物在焊缝凝固过程中形成并具有较大尺寸,数量较小;大量的细小二次碳氮析出物能在热处理后大量弥散析出,对基体产生明显的沉淀强化作用,在增强堆焊合金硬度减小磨粒锲入深度的同时有效阻碍磨粒的切削,从而获得高的耐磨粒磨损性能.     

Microstructural characterization and abrasive wear performance of HVOF sprayed Cr3C2–NiCr coating

Cr₃C₂–NiCr coatings were deposited by high velocity oxy-fuel (HVOF) process with different spray parameters to examine dominant microstructural factors in abrasive wear of the coatings. The microstructure of the HVOF sprayed Cr₃C₂–NiCr coatings was characterized by scanning electron microscopy and transmission electron microscopy (TEM). The apparent average size and volume fraction of carbide particles in the coatings were estimated through a quantitative imaging analysis. The formation of carbide phases in the coating was discussed based on the TEM observation results. The abrasive wear behavior of the coating was evaluated by the dry rubber wheel abrasive wear test and the wear mechanisms were elucidated. Influences of apparent size and volume fraction of carbide particles on the abrasive wear weight loss were examined through correlating the proposed relation with the experimental results. Results showed that Cr₃C₂ particle size was significantly reduced after the spraying and Cr₇C₃ carbide was present around Cr₃C₂ particles, and Cr₂₃C₆ carbide was dispersed in NiCr alloy matrix with a nano-crystalline structure. The three carbides were formed in the coating through different mechanisms. The removal of carbide particles in the coating was mainly responsible for the abrasive wear of the coating. The content and particle size of the Cr₃C₂ carbides were the two key factors controlling the abrasive wear of the HVOF sprayed Cr₃C₂–NiCr coatings.     

Influence of WC addition in Co-Cr-W-Ni-C flame sprayed coatings on microstructure, microhardness and wear behaviour

In present paper the influence of the tungsten carbide (WC) particle addition on the microstructure, microhardness and abrasive wear behaviour of flame sprayed Co-Cr-W-Ni-C (EWAC 1006) coatings deposited on low carbon steel substrate has been reported. Coatings were deposited by oxy-acetylene flame spraying process. Wear behaviour of coatings was evaluated using pin on flat wear system against SiC abrasive medium. It was observed that the addition of WC particle in a commercial Co-Cr-W-Ni-C powder coating increases microhardness and wear resistance. Wear behaviour of these coatings is governed by the material parameters such as microstructure, hardness of coating and test parameters (abrasive grit size and normal load). Addition of WC in a commercial powder coating increased wear resistance about 4-9 folds. WC modified powder coatings showed better wear resistance at high load. Heat treatment of the unmodified powder coatings improved abrasive wear resistance while that of modified powder coating deteriorated the wear resistance. SEM study showed that wear of coatings largely takes place by microgroove, crater formation and scoring. Electron probe micro analysis (E.P.M.A.) of unmodified and WC modified powder coating was carried out for composition and phase analysis.     

WC颗粒／高铬铸铁表面复合材料的应用研究

利用涂覆铸造技术,在灰铸铁表面以WC颗粒增强相／高铬铸铁复合制成耐磨衬板,与球墨铸铁、中锰耐磨铸铁对比试验和装机运行表明,复合材料的耐磨性有较大幅度的提高。在复杂的服役条件下,复合材料衬板的耐磨性具有良好的组织基础,制作工艺简单,有实际应用价值。     

WC颗粒/高铬铸铁表面复合材料的应用研究

利用涂覆铸造技术，在灰铸铁表面以WC颗粒增强相／高铬铸铁复合制成耐磨衬板，与球墨铸铁、中锰耐磨铸铁对比试验和装机运行表明，复合材料的耐磨性有较大幅度的提高。在复杂的服役条件下，复合材料衬板的耐磨性具有良好的组织基础，制作工艺简单，有实际应用价值。     

热喷涂NiCrBSi基耐磨涂层的研究进展

磨损失效是工业生产及材料使用寿命最主要的消耗方式之一,通过热喷涂表面涂层技术提高摩擦副表面摩擦磨损性能受到越来越多的关注。作为一种重要的表面处理技术,热喷涂在防腐、耐磨等方面均有出色的表现。NiCrBSi是以Ni、Cr为主要组元的Ni基自熔性合金,近年来,NiCrBSi基涂层在制备方法、性能表征和应用推广等方面都取得了重要进展。本文主要论述了热喷涂NiCrBSi和NiCrBSi-Mo涂层的自润滑性能、NiCrBSi-碳化物涂层的硬质相增强效果、NiCrBSi-氧化物涂层综合性能等方向的研究现状,分别对火焰重熔、激光重熔、炉内重熔及感应重熔NiCrBSi基涂层的原理、特点及相关应用实例进行了阐述,分析了这四种后处理重熔态涂层结构与磨损性能,着重比较添加组元和重熔工艺对涂层的组织结构、力学性能和耐磨损性能等方面的影响规律,并阐明了各自在机理上的异同。最后总结了NiCrBSi基耐磨涂层研究面临的主要问题,并针对这些问题,从材料、工艺和后处理方面提出了三点展望性建议。     

钒对铁基碳化钨耐磨堆焊层组织和性能的影响

在自研制的碳化钨管状药芯焊条中添加不同含量的钒元素（0%~3%）并制备堆焊合金,通过SEM,XRD,EDS等研究分析手段,研究不同钒含量对碳化钨耐磨层组织性能的影响规律.结果表明,钒含量与堆焊层中碳化钨颗粒的溶解程度密切相关,钒优先将碳化钨颗粒分解出的碳原子以碳化钒形式固定,从而抑制了碳化钨颗粒的分解,钒元素含量决定了碳化钨溶解的强弱,含有2%钒元素的堆焊层中生成适量碳化钒有效抑制了碳化钨的溶解.钒元素的加入还能强化碳化钨堆焊层基体金属的硬度,降低堆焊层中碳化钨颗粒剥落的风险,有效提高了堆焊层的耐磨性.     

纳米Al2O3-40％TlO2复相陶瓷颗粒增强镍基合金复合涂层的摩擦学性能

运用等离子喷涂技术在7005铝合金表面制备Al2O3-40%TiO2纳米结构颗粒增强镍基合金复合涂层,分析其微观结构,研究其在不同载荷和速度条件下的摩擦磨损性能。结果表明：复合涂层主要由γ-Ni、α-Al2O3、γ-Al2O3和金红石型-TiO2等相组成,其摩擦因数和磨损失重较镍基合金涂层显著降低。在轻载3 N 时,复合涂层磨损表面的接触应力较低,主要发生微观切削磨损;当载荷上升至6~12 N时,接触应力高于磨损表面的弹性极限应力,复合涂层的磨损机理变为多次塑变磨损、微观脆性断裂磨损和磨粒磨损。随着速度的增大,磨损表面的接触温度逐渐升高,复合涂层以多次塑变磨损、疲劳磨损和粘着磨损为主。     

Tribological behavior and mechanism of NiCrBSi–Y2O3 composite coatings

The NiCrBSi–Y₂O₃ composite coatings were prepared on the surface of 45 carbon steel by plasma spray, the microstructure and tribological properties of the coatings were investigated. The results show that the NiCrBSi–Y₂O₃ composite coatings are mainly composed of γ-Ni, CrB, Cr₇C₃ and Y₂O₃. With addition of Y₂O₃, hard phases such as CrB, Cr₇C₃ emerge in composite coating, and the density of the composite coatings also increases. The NiCrBSi–0.5Y₂O₃ composite coating presents excellent tribological properties. Its friction coefficient is 0.175, which is about 37% of that of the pure NiCrBSi coating. The mass wear loss is 1.2 mg, which is reduced by 43% compared with the pure NiCrBSi coating. When the loads are 6–10 N, the NiCrBSi–0.5Y₂O₃ composite coating suffers from slight wear and the wear mechanisms are mainly adhesive wear accompany with slight micro-cutting wear and micro-fracture wear. As the load increases to 12 N, the wear mechanisms are adhesive wear and severe micro-cutting wear.     

Microstructure and Tribological Properties of WC-CeO2/Ni- base Alloy Composite Coatings

运用等离子喷涂技术在7005铝合金表面制备了WC和CeO2颗粒协同增强镍基合金复合涂层,研究了该复合涂层的微观结构和摩擦学性能。结果表明:加入CeO2颗粒细化了复合涂层的显微组织,使WC增强颗粒从圆形变为不规则多边形,并降低了其脱碳分解程度。不同PV值摩擦条件下,WC-CeO2/镍基合金复合涂层的摩擦系数和磨损失重均低于WC/镍基合金复合涂层和镍基合金涂层。PV值小于3.36 N·m/s时,复合涂层磨损表面的最大接触应力低于其弹性极限接触应力,主要发生微观切削磨损和疲劳磨损;PV值大于3.36N·m/s后,磨损表面的最大接触应力超过其弹性极限接触应力,接触温度也急剧上升至648℃,磨损表面出现明显的塑性变形和脱落,其磨损机制变为多次塑变磨损、磨粒磨损和粘着磨损,并伴有氧化磨损。     

石墨含量对石墨/TiC/镍基合金复合涂层微观组织与摩擦学性能的影响

为了降低TiC/镍基合金复合涂层的摩擦因数并增强其耐磨性能,运用等离子喷涂技术在45#钢表面制备石墨/TiC/镍基合金（GTN）复合涂层。研究石墨含量对GTN涂层组织和摩擦学性能的影响。结果表明,石墨的加入有效地降低了涂层的摩擦因数,提高了其耐磨性。6.56GTN涂层和12.71GTN涂层分别在低载荷与高载荷摩擦条件下呈现出优异的减摩耐磨性能。在低载荷条件下,GTN涂层的磨损机理主要表现为多次塑变磨损,伴有轻微的磨粒磨损,且随着石墨含量的增加逐渐转变为多次塑变、层脱和微切削磨损;在载荷增加后,脆性断裂、微观切削和粘着为其主要的磨损机理,且随着石墨含量的增加逐渐转变为微观切削和脆性剥落。