Effect of Nb addition on microstructure and properties of laser cladding NiCrBSi coatings

NiCrBSi coatings with different Nb additions have been prepared by laser cladding. The microstructure, phase composition, hardness, and wear resistance of the coatings were studied by scanning electron microscopy (SEM), electron probe microanalyser (EPMA), X-ray diffraction (XRD), microhardness tester and M-200 wear tester. The results show that the phases in the NiCrBSi coating without Nb addition include γ-Ni, Cr₂₃C₆, Cr₇C₃, Ni₃B, Ni₃Si₂ and CrB. The NbC phase appears in coatings after the addition of Nb element. When the addition of Nb is 2?wt-%, the NbC particles with a size of about 1.2?μm were found in the coating, and the amount of NbC is about 1.8?vol.-%. With the increase of Nb addition, the size and amount of NbC in the coatings also increased. When the addition of Nb is 6?wt-%, the size of NbC is about 2.3–6.1?μm and the morphology of NbC changed from particle to quadrangular and petaloid shaped. In addition, when the addition of Nb is 2?wt-%, the hardness and wear resistance of the coating are the best, and the wear resistance of the coating is 104% higher than that without Nb addition.     

Effects of alloy elements on microstructure and crack resistance of Fe-C-Cr weld surfacing layer

0　IntroductionFe C Crsurfacingalloysarewidelyusedinindustries ,mainlyduetotheirhighwearresistance .Underconditionsofabrasiveenvironments,theeffectofcompositionandmi crostructureontheabrasionresistancehasbeenextensivelystudied[1～4 ] .TheauthorsalsoevaluatederosionresistanceofFe C Crweldsurfacinglayersbecausealargenumberofma chinecomponentssufferedfromsevereerosion ,suchasper cussiveplate ,rotorbladeandexhaustpipe ,etc .However,thelowcrackresistanceofFe C Crweldsurfacinglayershasbecomethei…     

Fe-Cr-C-B-Nb堆焊合金的显微组织和耐磨性

采用明弧自保护法制备Fe-Cr-C-B-Nb系耐磨堆焊合金,借助光学显微镜(OM)、扫描电镜(SEM)和X射线衍射(XRD)等手段,分析堆焊层中的物相组成,探究熔池中硬质相析出顺序,研究B和Nb元素含量对其显微组织和耐磨性影响. 结果表明,制备的堆焊合金显微组织为马氏体+残余奥氏体+ M23(C,B)6+NbC,NbC先于M23(C,B)6生成. 当堆焊层中B元素含量为0.21%,Nb元素含量为1.44%时,可以使堆焊合金有较高的硬度和耐磨性. 洛氏硬度可达69 HRC±1.5 HRC,磨损量为0.037 6 g. 过量的B元素不利于NbC析出,而使Nb元素固溶强化硼化物和基体. 耐磨性试验结果表明,M23(C,B)6和NbC两种硬质相显著改善了Fe-Cr-C-B-Nb系堆焊合金的耐磨性.     

Microstructure and wear mechanism change by Nb added in slag free self-shielded flux cored wire

Abstract

The iron based hardfacing alloys were produced using slag free self-shielded flux cored wires with varying niobium contents. The results show that NbC acted as the nucleus of primary M₇(C, B)₃ (M?=?Cr, Fe mainly) carbides and decreased the amount of M₇(C,B)₃ carbides when niobium was added into the alloys. When 18?wt-%Fe–Nb (60?wt-%Nb) was added, the microstructure of hardfacing alloy transformed from hypereutectic structure to a eutectic one due to the formation of NbC, which consumed a mass of carbon. The microstructure changed into a hypoeutectic structure when the Fe–Nb content was up to 24?wt-%. With the increase in Fe–Nb content, the main abrasive wear mechanism changed from microcracking to microcutting and microploughing due to the formation of NbC and the reduction of primary M₇(C, B)₃ carbides. The wear loss of the alloy with 18?wt-%Fe–Nb addition was the smallest among all the alloys.     

Microstructure and wear resistance of highchromium cast iron containing niobium

In the paper, the effect of niobium addition on the microstructure, mechanical properties and wear resistance of high chromium cast iron has been studied. The results show that the microstructure of the heattreated alloys is composed of M7C3 and M23C6 types primary carbide, eutectic carbide, secondary carbide and a matrix of martensite and retained austenite. NbC particles appear both inside and on the edge of the primary carbides. The hardness of the studied alloys maintains around 66 HRC, not significantly affected by the Nb content within the selected range of 0.48%-0.74%. The impact toughness of the alloys increases with increasing niobium content. The wear resistance of the specimens presents little variation in spite of the increase of Nb content under a light load of 40 N. However, when heavier loads of 70 and 100 N are applied, the wear resistance increases with increasing Nb content.     

Enhancement of wear resistance and impact toughness of as cast hypoeutectic high chromium cast iron using niobium

The effect of niobium additions on the as-cast microstructure of a hypoeutectic high-Cr cast iron containing 2.2 wt.% C and 16.5 wt.% Cr was investigated. With increasing niobium content, the eutectic M₇C₃ carbides were refined and became less elongated as well as its volume fraction was decreased gradually. The first precipitated NbC particles could be act as heterogeneous substrate of proeutectic austenite and a barrier to M₇C₃ grain growth. The morphology of NbC carbides changed with increasing niobium content. Such NbC particles were increased with increasing Nb content and subsequently contributed to increased hardness. Optimum toughness was obtained for the irons alloyed with 2.14% Nb. The effects of applied load and Nb-additions on wear resistance of high chromium cast iron have been studied. The results showed that wear resistance increases with increasing Nb addition. Furthermore, the effectiveness of the NbC particles on the weight loss was more evident at higher loads.     

等温淬火处理对感应重熔镍基合金涂层摩擦学性能的影响

目的改善镍基合金涂层的摩擦学性能。方法分别采用感应重熔工艺及感应重熔-等温淬火一体化工艺,在GCr15钢基体表面制备了两种镍基合金涂层,并通过销盘摩擦磨损试验、扫描电子显微镜、X射线衍射仪、显微硬度测试对其摩擦磨损性能、微观组织、表面硬度进行了对比研究,探讨了等温淬火处理对感应重熔镍基合金涂层摩擦学性能、微观组织、表面硬度的影响,揭示了其增强机理。结果经等温淬火后的重熔涂层比感应重熔涂层具有更低的摩擦系数和磨损失重,摩擦稳定阶段的摩擦系数为0.301,比后者低23.8%,相对耐磨性是后者的1.71倍。感应重熔涂层同时存在着磨粒磨损和粘着磨损两种机制,而经等温淬火后的重熔涂层以磨粒磨损为主,比前者具有更优异的抵抗磨粒磨损和粘着磨损的能力。感应重熔涂层及经等温淬火处理后的重熔涂层平均显微硬度分别为818.0、873.6HV(0.5),硬度极差分别为170.9、132.6HV(0.5),形状参数分别为18.5057、22.6189,后者比前者具有更高的平均硬度值、更小的硬度极差以及更加稳定的涂层性能。经过微观组织分析发现,重熔涂层在经等温淬火处理后,其晶粒的细化、硬质相的相对均质弥散性、共晶相的减少、丰富的耐磨陶瓷相和快速凝固的定向晶粒结构的协同作用,是其具有优异的显微硬度Weibull分布特性,以及耐磨性得到进一步提高的根本原因。结论合适的等温淬火热处理工艺能够改善感应重熔镍基合金涂层的微观组织,从而有效减小其摩擦系数,并提高其耐磨性。     

Ti和Nb对铁基堆焊合金组织性能的影响

改变Ti或Nb的添加量制备Fe-Cr-C-B系铁基堆焊合金.借助扫描电镜、X射线衍射仪、洛氏硬度计和磨损试验机对堆焊合金组织性能进行测试分析.结果表明,在含Ti或Nb的堆焊合金中,初生奥氏体晶粒细化,共晶组织呈断网状均匀分布,并分别有黑色圆形或块状TiC和菱形或三角形NbC硬质相颗粒生成,添加5%Ti的堆焊合金组织最细小.TiC或NbC硬质相颗粒在组织中呈均匀弥散分布,能够作为耐磨质点与细化的初生奥氏体和共晶组织构成耐磨骨架,共同抵抗磨粒的楔入与切削作用.当Ti添加量为5%时,含Ti堆焊合金达到最优耐磨性,硬度为66 HRC,磨损量为0.048 7 g;当Nb添加量为4%时,含Nb堆焊合金达到最优耐磨性,硬度为65 HRC,磨损量为0.052 4 g.在同等条件下,含有适量Ti的铁基堆焊合金具有更优的耐磨性.     

激光熔敷Ni基合金涂层的腐蚀磨损性能研究

系统研究了２１－４Ｎ阀门钢表面激光敷Ｎｉ基ＷＣ合金,Ｎｉ基ＷＣ稀土（ＣｅＯ２）合金涂层,在不同冲击速度和腐蚀介质浓度下的动腐蚀、动磨损和腐蚀磨损性能。试验结果表明,激光熔敷层的腐蚀磨损性能优于２Ｃｒ１３钢,Ｎｉ６０＋２０％ＷＣ＋０．５％ＣｅＯ２具有最佳的抗腐蚀磨损性能。根据试验结果,用多元回归分析方法分别建立了冲击速度,介质浓度与腐蚀磨损速率之间,动腐蚀速率,动磨损速率与腐蚀磨损速率间的定量关系,     

Non-vacuum sintering process of WC/W2C reinforced Ni-based coating on steel

Ni-based composite coatings containing varied contents of tungsten carbides on low carbon steel were fabricated. Effects of sintering temperature and tungsten carbides contents on the surface, interface, microstructure and wear resistance of the coatings were investigated using scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, Vickers microhardness tester, bulk hardness tester and pin-on-disc tribometer. The results indicated that with appropriate sintering temperature (1230 °C), smooth coating surfaces can be achieved. Favorable interfaces about 200 μm can be got that both the chemical composition and property of the interfacial region showed gradual transitions from the substrates to the coatings. Microstructure of the coatings consists of tungsten carbides and M7C3/M23C6 in the matrix. With excessive sintering temperature, tungsten carbides tend to dissolve. Ni-based coatings containing tungsten carbides showed much higher level of bulk hardness and wear resistance than ISO Fe360A and ASTM 1566 steels. With increasing contents of tungsten carbides from 25% to 40%, bulk hardness of Ni-based coatings gradually increased. Ni-based coating with 35% tungsten carbides performed the best wear resistance.     

Effect of Ti-V-Nb-Mo addition on microstructure of high chromium cast iron

The effects of trace additions of multi-alloying elements (Ti,Nb,V,Mo) on carbides precipitation and ascast microstructure of eutectic high chromium cast iron containing 2.85wt.％C and 31.0wt.％Cr were i...     

Characteristics of Fe-based WC Composite Coatings Prepared by Double-pass Plasma Cladding Process

The Fe-based WC composite coatings were clad on Q235 steel by double-pass plasma cladding method,in which the WC-Co(WC covered with cobalt:78wt%WC,12wt%Co)doping was about 10wt%,20wt%and 40wt%,respectively.The microstructure and wear performance of the composite coatings were investigated by X-ray diffraction(XRD),scanning electron microscope(SEM),energy dispersive spectrometer(EDS)and ball-disc wear tests.The results show that the clad coatings contain mainly?-Fe,WC and carbides(Cr23C6,Fe3W3C-Fe4W2C)phases and the precipitation of carbides increases with the increase of WC-Co doping content.The WC-Co doping content has an obvious effect on the microstructure of the clad coatings.For the clad coatings with low WC-Co doping,the microstructure gradually transforms from planar crystal at the interface of substrate/coating to cell/dendritic crystal at the middle and the upper portion of the coatings.But there are a number of fishbone-like structure at the middle and the upper portion of clad coating with 40wt%WC-Co doping.The microstructure at the top is smaller than that at the bottom for all the coatings.The maximum of hardness of the clad coatings is 72.3HRC which is about 6.9 as much as the hardness of Q235 steel substrate.The composite coatings have good wear resistance due to the reinforcement of carbide particles and the strong bonding between carbide particles and ferroalloy.The suitable increase of WC-Co doping content can improve the wear resistance of the composite coatings.     

激光熔覆(Ni60+NbC)+h-BN@Cu涂层组织与性能研究

目的 通过添加铜包覆六方氮化硼(h-BN@Cu)粉末,改善激光熔覆Ni基NbC涂层的性能。方法 采用激光熔覆技术,使用添加不同质量分数铜包覆六方氮化硼的镍基碳化铌复合粉末,在45钢基体表面沉积镍基复合涂层。利用扫描电子显微镜(SEM)和X射线衍射(XRD)设备,研究h-BN@Cu对Ni60/NbC的激光熔覆镍基复合涂层微观结构的影响,利用显微硬度计和布鲁克UMT-2摩擦磨损试验机及白光干涉模块,测量熔覆层的显微硬度、摩擦磨损系数和磨痕宽度。结果 熔覆层中的主相为Ni-Cr-Fe,除此之外还存在FeNi3、CrB、M7C3、NbC、M23C6、Cr2Nb等多种相。研究发现,添加的润滑相h-BN@Cu与硬质相NbC会发生部分分解,Nb原子和B原子进入熔池,与熔池中的Cr原子反应,生成CrB、Cr2Nb等,这些金属间化合物具有硬度高、耐磨性好等特点。当h-BN@Cu的质量分数为10%时,熔覆层的显微硬度为650HV1.0,摩擦系数为0.4,磨痕宽度为0.406 mm。结论 相比于不添加h-BN@Cu的Ni60/NbC熔覆层,添加h-BN@Cu的Ni60/NbC熔覆层的平均硬度略微下降,但熔覆层硬质相分布更加均匀,此时硬度仍为45钢基体硬度的3.1倍,摩擦系数降低约27%,磨痕宽度减小约21%。     

Effects of molybdenum on the microstructure and wear resistance of nickel-based hardfacing alloys investigated using Rietveld method

The nickel-based hardfacing alloys with different Mo contents have been deposited on Q235-carbon steel using a plasma transferred arc (PTA) welding machine. The effects of Mo on the microstructure and wear resistance properties of the nickel-based hardfacing alloys were investigated using optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD). More detailed information about the crystallographic structure and phase compositions of the deposited coatings was obtained with the application of Rietveld refinement method to analyze XRD spectra. It was found that the addition of Mo did not lead to a change in phase compositions. Furthermore, it can also be seen that the relative contents of the total Cr-rich compounds increased from 36 wt.% to 45 wt.%, though the M₂₃C₆ type carbide increased but the relative contents of the M₇C₃ type carbide decreased with the increasing of Mo contents from 0 wt.% to 6 wt.%. The component segregation, which existed in the Mo-free coating, decreased gradually then disappeared finally with the increasing of Mo contents. The morphology of Cr-rich compounds observed in the interdendritic region changed from plate-like to net-like, as well as the refinement of Ni-rich dendrites because of the addition of Mo. The wear resistance increased but the microhardness decreased with the increasing of Mo contents from 0 wt.% to 6 wt.%. The microstructural change and phase contents variation were responsible for the improvement of the mechanical properties such as wear resistance of the Mo-modified nickel-based hardfacing alloy.     

WC-6%Co硬质合金的冲击磨粒磨损性能研究

用MLD-10型动载磨粒磨损试验机研究了不同晶粒度YG6硬质合金的冲击磨粒磨损性能。对试样进行了失重测量,并用FESEM分析磨损试样表面形貌。结果表明,硬质合金的耐磨性能与粘结相自由程、WC晶粒度有关;在本实验条件下,随着WC晶粒度或粘结相自由程增加,合金耐磨性先增加后减小,特定WC晶粒度配比的混晶WC-6%Co合金的抗冲击耐磨性能最好。合金的磨损失效机制也发生了转变:细晶合金主要表现为WC颗粒的剥落;随WC晶粒度增加,合金主要表现为大颗粒WC破碎后脱落。在以SiC为磨料的冲击磨粒磨损试验中,WC-6%Co合金的磨损是以WC颗粒的破碎和碎片脱落为主要的失效机制。     

B4C对激光熔覆钴基合金涂层组织与耐磨性的影响

运用5kWcO2连续激光器在低碳钢表面激光熔覆Co基合金涂层(C065)及Co基合金中添加20％B4C(体积分数)的复合涂层(B4C／Co),研究了B4C对熔覆层组织、显微硬度及耐磨性的影响。结果表明,两种熔覆涂层均为树状枝晶生长的亚共晶组织。C055涂层主要由大量初生枝晶γ固溶体及其间的共晶组织1与(Cr,Fe)7C3组成;B4C／Co涂层主要由γ-Co,Cr7C3,Cr23c6,CrB2和Fe23(C,B)6组成,添加的B4C粒子在熔覆过程中全部熔解,但B4C／Co涂层组织与C055相比明显细化。B4C／Co涂层的显微硬度及耐磨性比Co65涂层都明显提高,并分析了涂层的强化机理。     

Microstructures and wear resistance of high boron and low carbon ferroalloy using hybrid powder/ wire overlaying method

The high boron alloy surfacing layer was easily cracked due to its insufficient toughness by using hybrid powder/wire overlaying method. In order to explore the cracked mechanism, the microstructures and the wear resistance of the samples with different boron contents were studied. Further, phases analysis, microhardness, macrohardness and wear test were also carried out. The boron content depended microstructures were observed. The precipitation of the Fe ₂ B, Fe ₃ ( C, B) , Fe ₂₃ ( C, B) ₆ were increased with the increase of boron content. It was found that the wear resistance was independent of the macrohardness as the macrohardness increased firstly and then remained steady at ~ 62 HRC. However, the wear resistance was depended on the boron contents, and which increased with the increase of the boron contents. The abrasive loss mechanism changed from plastic deformation removal to fracture removal.     

V / Nb 对电弧喷涂马氏体不锈钢合金涂层组织和性能的影响

目的 研究添加 V 和 Nb 对电弧喷涂马氏体不锈钢合金层组织和性能的影响规律。 方法 研制不同 V 和 Nb 含量的新型马氏体不锈钢电弧喷涂药芯丝材,利用高速电弧喷涂设备在 Q235 低碳钢板表面制备耐磨合金涂层,并对合金涂层的组织结构和性能进行研究。 结果 所制备的合金涂层成形良好,孔隙率较低,结构致密;涂层显微硬度值达 523 HV0 . 1 ,与基材间的平均结合强度值达 35 . 48 MPa,V 和 Nb的添加提高了合金涂层的耐磨损性能。 结论 添加适量的 V 和 Nb 合金元素,可以促进碳化物硬质相颗粒的形成,提高马氏体不锈钢合金涂层的综合性能。     

一种新型镍基高温合金组织及性能的研究

GH4742(俄ЭП742)合金属于典型的高合金化难变形镍基高温合金涡轮盘材料,本文通过调整Al、Ti、Nb的成分对GH4742合金进行改进,发明了一种新型镍基高温合金。利用JMatPro模拟得到平衡相图,再利用光学金相显微镜和场发射扫描电镜对合金的晶粒组织、碳化物以及γ′相分布情况进行观察,同时对力学性能进行了检测。结果表明：平衡状态下的合金从1 400 ℃到300 ℃的冷却过程中相转变可概括为L → L+γ → L+γ+MC →γ+MC+γ′ → γ+γ′+MC+μ → γ+γ′+μ+MC+M23C6 → γ+γ′+μ+MC+M23C6+σ,780 ℃下析出γ′相的质量分数为40.88%;锻造变形工艺为γ+γ′双相区变形,1 120 ℃固溶后经过标准双时效处理(850 ℃/6 h/AC＋780 ℃/6 h/AC)后的显微组织明显可见两种不同尺寸晶粒,小晶粒(13 μm)呈项链状分布于大晶粒(100 μm)周围;该合金中的碳化物主要为大尺寸、不规则形状的MC(NbC、TiC、VC),断续穿晶和沿晶分布;强化相γ′相的分布状态也有大小两种不同尺寸,γ′I相平均直径为600 nm,γ′II相平均直径为150 nm,两种尺寸γ′相强化的良好匹配,使得该合金在具有较高强度的同时又具有较高的塑性,力学性能优异,室温抗拉强度1 478 MPa,尤其是650 ℃/863 MPa下的持久性能为194 h,远远超过GH4742合金650 ℃/823 MPa持久下50 h的标准。