热反应扩散时间对钒铬共渗层显微形貌及性能的影响

近年来,铬钒共渗层由于具有优良的综合性能被逐渐关注并广泛研究与应用,但已有的报道对其显微形貌尤其是界面结构以及性能的研究较少。采用热反应扩散法对Cr12钢进行铬钒共渗处理,利用光学显微镜(OM)、扫描电镜(SEM)、X射线能谱仪(EDS)、X射线衍射仪(XRD)对渗层的显微结构进行了分析。重点讨论了热反应扩散时间对渗层厚度、显微硬度、物相组成以及膜基结合力的影响;分析了主要元素沿渗层到基体方向的变化趋势和特点。结果表明:随着渗入时间的延长,所得渗层的厚度为2.0~8.2μm,渗层连续、均匀较致密。铬钒共渗层的物相组成主要为VC、Cr7C3和(Cr,Fe)7C3,反应过程中各物相对应的衍射峰强度会发生相应的变化。渗层的显微硬度值为1 683.80HV0.3~1 948.57HV0.3,明显高于空白基体的显微硬度值;划痕测试结果表明铬钒共渗层和基体的界面结合良好,结合力为55~64N。     

钛合金表面等离子体电解氮碳共渗的研究

在含有硝酸铵、甘油、乙醇的水溶液中,利用等离子体电解渗入技术在Ti6Al4V钛合金表面制备了氮碳共渗层.利用SEM、XRD、GDS以及显微硬度计分析了渗层的形貌、成分、组织和显微硬度,探讨了渗层形成的机理和过程.结果表明:(1)以300V的电压经45min处理制备的渗层总厚度约为100μm,其中化合物层约为20μm,主要由Ti(C,N)相组成;(2)渗层最高显微硬度超过2000HK0.0025.等离子体电解渗入技术可以较快地在钛合金表面制备出厚度大、硬度高的氮碳共渗层.     

温度对40Cr13钢等离子表面渗铌层组织的影响

为提高马氏体不锈钢的耐蚀和耐磨性能,选择40Cr13不锈钢为基材、纯铌板为靶材,采用双辉等离子表面冶金技术在不锈钢表面制备合金化层.用SEM、GDOES、XRD等方法分析渗铌温度对铌合金层组织、成分、相组成、表面形貌及硬度的影响,并对渗层形成机制及表面硬化机理进行了研究.结果表明:在900~1 000℃形成的铌合金层组织均匀致密,合金层主要由Nb2C、Nb C、Fe2Nb、Cr2Nb及铌组成;合金层表面粗糙度随渗铌温度的提高而增加;合金层厚度随渗铌温度改变发生不同变化规律,950℃渗铌形成的渗层约13μm,900和1 000℃渗铌后合金层厚度均为7μm左右;不同温度渗铌后试样的表面硬度与基体相比均有较大幅度的提高,1 000℃渗铌后试样表面硬度高达约985 HV0.025,900℃渗铌后约758 HV0.025,而950℃渗铌后表面硬度最低,约698 HV0.025.     

T10钢低温双辉等离子表面渗镀铬硬化的研究

采用双辉等离子渗铬技术,首先在560℃对T10钢进行不同时间的渗铬,再对已渗铬试样进行4h离子氮化,研究了该工艺对渗镀铬层硬化效果的影响.结果表明:双辉渗铬后的渗层由厚3～5μm的沉积层+扩散层组成,沉积层组织致密并与基体结合良好,基体组织和晶粒度与渗铬前基本一致;沉积层铬浓度达45%(质量分数)以上,内有20～25μm的扩散层,铬浓度向内呈梯度分布;表面物相均由Fe,Fe-Cr,Cr7C3,Cr23C6等组成;渗层表面显微硬度达650~850HV,向内逐步降低,呈梯度分布.沉积层厚度、渗层深度、渗层的铬浓度及显微硬度等均随渗铬时间的增加而增加.渗层经离子氮化后的组织与氮化前的组织无明显变化,但表面物相为Fe-Cr,Cr7C3,Cr23C6,CrN,Fe4N,表面显微硬度提高到1000~1350HV,较未氮化前提高约60%以上.     

BT20钛合金表面渗氧研究

氧与钛之间的亲合力比较高,利用这一点可以通过热处理的办法对钛及钛合金部件表面的硬度和耐磨性进行提高.将激光处理的和未经激光处理的BT20钛合金放置在一种特殊固体介质中于大气气氛下进行渗氧处理,来研究炉的加热条件和前处理过程对显微组织和硬度的影响.激光处理过的和未经激光处理的BT20钛合金在相同温度和处理时间的条件下进行渗氧以获得强化层.处理后外层为金红石型的TiO2,里层为由α-Ti组成的氧固溶强化层.激光处理的试样在渗氧后表面硬度最高可达到Hv628,厚度可以达到35μm,而未经激光处理的钛合金的表面硬度最高可以达到Hv580,膜厚度达到25μm .     

包埋法制备Zn-Ni渗层的结构及摩擦学行为研究

为了改善45钢表面摩擦磨损性能,采用粉末包埋法,在45钢表面制备出Zn-Ni渗层.利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、能谱仪研究了Zn-Ni渗层的厚度、显微形貌、物相组成和元素分布,采用显微维氏硬度计测定渗层的硬度,并通过多功能材料表面性能测试仪测试渗层与3种不同对摩球GCr15、Al2O3、Si3N4之间在不同正压力下的摩擦磨损性能.结果 表明:Zn-Ni渗层的厚度约为98 μm;渗层物相组成主要为FeZn10.98和FeZn8.87;Zn-Ni渗层截面硬度范围为358～615 HV0.98N;Zn-Ni渗层在往复摩擦试验中,与GCr15对摩球进行往复摩擦时主要是黏着磨损和磨粒磨损,与Al2O3对摩球进行往复摩擦时主要是磨粒磨损,与Si3N4对摩球进行往复摩擦时主要是摩擦化学过程.     

显微硬度法与纳米压入法测量微米级硬质薄膜硬度的比较

测定了离子束辅助沉积TiN,CrN薄膜的纳米压入硬度（Hnano值）、维氏显微硬度（Hv值）和努氏显微硬度（HK值）。结果发现,HK值比Hv值更接近于Hnano值,相对较为准确。膜的厚度（t）越薄,三种方法测得硬度值差别越大;膜的厚度越厚,差别越小。随着膜的厚度增加,Hk值和Hv值逐渐接近Hnano值。t≈5．0μm时,Hv≈HK≈Hnano对于硬膜软基体模型,如果膜厚〉5．0μm,可以采用显微硬度计较为准确地测量薄膜硬度;膜厚〈5．0μm时,应避免使用显微硬度法而采用纳米压入法。     

45钢低温双辉等离子渗铬硬化的研究

常规双辉等离子渗铬温度较高(800℃以上),能耗较大.为此,采用双辉等离子渗金属技术,在560℃下对45钢进行了表面渗铬硬化,制备出了性能良好的表面合金改性层.采用X射线衍射仪及其附带的能谱仪测定了渗层物相及成分,采用金相显微镜考察了渗层组织形貌,并采用显微硬度计检测了渗层硬度.结果表明:渗层组织由沉积层及扩散层组成;渗层表层为2～3 μm的沉积层,含铬量达到48%以上,沉积层致密并与扩散层结合紧密;内有20～25 μm的扩散层,其合铬量呈梯度分布;表面物相由Fe-Cr、Cr7C3、Cr23C6等组成;渗层表面显微硬度达600～700 HV,硬度向内呈梯度分布.     

混凝土桥梁金属配件粉末渗锌防腐蚀层研究

实验室小型共渗炉内制备的试样与工业化渗层试样在结构和性能方面不同。为更合理地评价工业化渗层质量,通过工业随炉共渗制备渗锌小尺寸试样,分析了渗锌防腐蚀层的厚度、微观结构、元素分布、硬度,并测试其耐盐雾性能。结果表明:渗锌后工件表面结构可分为Zn-Fe合金层和含Zn过渡层,Zn-Fe合金层在表层,Zn含量较高,是防腐蚀防锈的主要结构层; Zn-Fe合金层与铁基体的界面过渡层厚度约20μm,Zn-Fe合金层与基体结合紧密;渗锌温度高、保温时间长有助于提高工件表面渗层厚度,随炉渗锌小尺寸试样增重法测得的渗层厚度最小,较适用于监控每炉工件共渗质量;合金层硬度高于基体,硬度向基体方向逐步降低,合金层和离界面60μm处的硬度均高于基体30 HV以上,可提高工件表面的耐磕碰性能;常用渗锌温度(420℃)热处理对工件表面硬度无影响,渗锌工件表面硬度增加主要在于表面形成了合金层;随着渗锌层厚度增加,渗层样品耐盐雾性能逐渐提高,渗层厚度宜≥60μm。     

包埋渗铝法制备Fe-Al渗层及其扩散机制

包埋渗铝法可在钢基体表面制备出一层致密、坚固、连续的Fe-Al渗层，以改善基体性能。本文在不同温度和不同时间下对Q235低碳钢进行包埋渗铝，形成Fe-Al渗层，采用X射线衍射、扫描电镜及能谱分析等方法研究了渗铝层的物相结构、表面及截面形貌和成分，采用显微硬度仪测量了截面硬度。结果表明，不同渗铝温度下获得的渗铝层，主要含有Fe₂Al₅和FeAl₃两相，且750℃得到的渗层存在较多Fe₂Al₅相；随着渗铝温度升高，Fe-Al渗层厚度增加，Al原子扩散系数增大，但显微硬度降低；不同渗铝时间下制备的渗铝层，物相仍以Fe₂Al₅和FeAl₃为主，但随着渗铝时间延长，FeAl₃含量减少，且Al原子扩散系数变大，渗层显微硬度略有降低。在进一步分析Fe-Al渗层形成的热力学与动力学基础上，总结了渗铝层形成的扩散机制。     

Fabrication of high hardness and corrosion resistance coatings from Fe-based alloy powders

Gas atomized Fe₅₀Cr₂₄Mo₂₁Si₂B₃ powders were used to form Fe-based alloy coatings by the air plasma spray method. The coatings exhibited high amorphous nature and extremely low porosity of 0.41% in about 200 µm thickness. The Fe-based coating exhibits an average hardness about 1255 Hv. The Fe-based coatings could be potentially applied as functional surface protective coatings.     

Magnetron sputtered NbN films with electroplated Cr interlayer

NbN films were deposited on SS substrates by reactive DC magnetron sputtering at various N₂ flow rates and substrate biasing. Coatings were studied for their thickness, structure, hardness and adhesion aspects. Process parameters were optimized for deposition of NbN coatings. NbN coatings were then extended on to MS substrates with Cr interlayer in three different thicknesses of 2, 4 and 10 μm. Cr was deposited by electroplating. The duplex coatings have been studied for the improvement with respect to surface hardness by Knoop micro indentation, adhesion by scratch testing and corrosion performance by potentiodynamic polarization technique. Open circuit potentials were also measured.     

Magnetron sputtered NbN films with electroplated Cr interlayer

NbN films were deposited on SS substrates by reactive DC magnetron sputtering at various N₂ flow rates and substrate biasing. Coatings were studied for their thickness, structure, hardness and adhesion aspects. Process parameters were optimized for deposition of NbN coatings. NbN coatings were then extended on to MS substrates with Cr interlayer in three different thicknesses of 2, 4 and 10 μm. Cr was deposited by electroplating. The duplex coatings have been studied for the improvement with respect to surface hardness by Knoop micro indentation, adhesion by scratch testing and corrosion performance by potentiodynamic polarization technique. Open circuit potentials were also measured.     

大功率CO2激光原位直接反应合成TiN/Ti 复合材料的研究

使用大功率CO₂激光原位直接反应合成TiN /Ti 复合材料, 分析了材料的微观结构、物相组成、成分及显微硬度分布。结果发现: 氮化层是富钛结构的, 由TiN 相和α-Ti 构成, TiN 以枝晶形式在氮化层均匀分布。材料横截面显微硬度连续变化。氮化层的氮化程度随激光作用时间的增加而增加, 辐照的激光能量密度越高, 氮化层的厚度越大。激光功率密度, 激光扫描速度, 氮气喷射压强分别为3. 35×105W·cm-2, 300mm·min-1, 0.35M Pa 时, 材料表面硬度值达到Hv1600, 氮化层的厚度有350Lm。      

X射线测量高速钢上不同厚度氮化钛涂层残余应力

采用多弧离子镀在AISIM2高速钢(HSS)上沉积了TiN硬涂层,试样中基体厚度为1mm,涂层厚度分别为3.0、5.0、7.0、9.0和11.0μm.应用X射线衍射(XRD)分析了TiN涂层中残余应力,测量了TiN(220)衍射晶面在五种不同倾斜角(Ψ=0°,20.7°,30°,37.8°和45°)下的X射线衍射峰.结果表明:在3～11μm涂层厚度范围内,TiN涂层中均表现出残余压应力且残余压应力值较大.TiN涂层中残余应力大致分布在-3.22～-2.04GPa之间,本征应力分布在-1.32～-0.14GPa,热应力约为-1.86～-1.75GPa.TiN涂层中残余应力值随涂层厚度变化是非线性增加的,随厚度增加表现出先增大后减小的变化趋势,多项式拟合后发现约在8.5μm厚时残余应力达到最大值.     

Microstructure and mechanical properties of nanostructure multilayer CrN/Cr coatings on titanium alloy

Five different nanostructured, multilayer coatings (CrN/Cr)x8 with different thickness ratio of Cr and CrN layers were deposited by PAPVD (Plasma Assisted Physical Vapour Deposition) vacuum arc method on Ti6Al4V titanium alloy. The microstructure, chemical and phase composition of the CrN and Cr sub-layers were characterized by SEM with EDX and Cs-corrected dedicated STEM on cross-sections prepared by focus ion beam. Besides, hardness and Young's modulus of the (Cr/CrN)x8 coatings has been measured. The adhesion has been tested by scratch test method. The obtained (CrN/Cr) multilayer coatings, 5-6 μm in thickness, have homogeneous and nanocrystalline structure, free of pores and cracks. The microstructures of Cr and CrN layers consist of columnar grains below 100 nm in diameter. The hardness and Young's modulus of these coatings depend linearly on thickness ratio of Cr and CrN layers. The decrease of the thickness ratio Cr/CrN 0.81 to 0.15 results in the increase of hardness from 1275 HV to 1710 HV and Young's modulus from 260 GPa to 271 GPa.     

KOH／K2ZrF6对TC4钛合金微弧氧化膜层形貌和结合强度的影响

研究电解液中添加KOH及K₂ZrF₆对TC4钛合金微弧氧化膜层形貌及结合强度的影响。选用硅酸盐-磷酸盐复合盐为主盐,添加甘油作为辅助试剂,分别配制两种均不添加、只添加KOH、只添加K₂ZrF₆和两种物质均添加的4种电解液对TC4钛合金进行微弧氧化处理。通过膜层厚度、膜层表面粗糙度、膜层硬度、膜层与基体的结合强度等检测,对比分析不同膜层的综合性能,并通过扫描电子显微镜、能谱仪及X射线衍射仪等对膜层物相进行对比分析。结果表明:在硅酸盐-磷酸盐复合盐为主盐的电解液中,氧化30 min后,添加KOH试剂使微弧氧化反应起弧电压从350 V降低至300 V,膜层表面粗糙度Ra为1.66μm,结合强度为29 MPa,膜层硬度866HV,厚度19μm。添加K₂ZrF₆试剂使微弧氧化的起弧电压提高至380 V,膜层表面粗糙度Ra为2.47μm,结合强度为18 MPa,膜层硬度992HV,厚度为26μm,同时,氧化反应生成ZrO₂,可大幅提高膜层硬度。添加KOH和K₂ZrF₆试剂可以影响微弧氧化反应起弧电压及工作电压,进而影响膜层的组织形貌,从而改善膜层的表面粗糙度和厚度以及结合强度,硬度等性能。     

Formation of high heat resistant coatings by using gas tunnel type plasma spraying

Zirconia sprayed coatings are widely used as thermal barrier coatings (TBC) for high temperature protection of metallic structures. However, their use in diesel engine combustion chamber components has the long run durability problems, such as the spallation at the interface between the coating and substrate due to the interface oxidation. Although zirconia coatings have been used in many applications, the interface spallation problem is still waiting to be solved under the critical conditions such as high temperature and high corrosion environment. The gas tunnel type plasma spraying developed by the author can make high quality ceramic coatings such as Al2O3 and ZrO2 coating compared to other plasma spraying method. A high hardness ceramic coating such as Al2O3 coating by the gas tunnel type plasma spraying, were investigated in the previous study. The Vickers hardness of the zirconia (ZrO2) coating increased with decreasing spraying distance, and a higher Vickers hardness of about Hv = 1200 could be obtained at a shorter spraying distance of L = 30 mm. ZrO2 coating formed has a high hardness layer at the surface side, which shows the graded functionality of hardness. In this study, ZrO2 composite coatings (TBCs) with Al2O3 were deposited on SS304 substrates by gas tunnel type plasma spraying. The performance such as the mechanical properties, thermal behavior and high temperature oxidation resistance of the functionally graded TBCs was investigated and discussed. The resultant coating samples with different spraying powders and thickness are compared in their corrosion resistance with coating thickness as variables. Corrosion potential was measured and analyzed corresponding to the microstructure of the coatings. Keywords: High Heat Resistant Coatings, Gas Tunnel Type Plasma Spraying, Hardness,