激光熔覆TiC-Ni复合涂层的摩擦磨损性能和磨损机制研究

利用光学显微镜和扫描电镜观察了钛合金表面TiC-Ni激光熔覆层的宏观形貌和微观组织,测试了激光熔覆层的硬度、摩擦系数和磨损量。利用SEM观察了磨损的表面形貌和磨屑的形貌,分析了激光熔覆层的磨损机制。结果表明:激光熔覆层组织致密,无气孔和裂纹,硬度为基材的3倍;激光熔覆层的摩擦系数随环境压力的降低而提高,磨损量随环境压力的降低、法向载荷的增加而增加;低载时为轻微的磨粒磨损,高载时为严重的剥层磨损。     

磁场辅助激光熔覆制备Ni60CuMoW复合涂层

采用磁场辅助激光熔覆技术,在Q235钢表面制备了Ni60CuMoW复合涂层,借助SEM,EDS 和XRD 等表征手段对涂层进行了微观组织和物相分析,利用维氏硬度计测试了复合涂层截面的显微硬度分布,通过摩擦磨损实验和电化学测试系统研究了复合涂层的磨损性能和耐腐蚀性能。研究结果表明：涂层主要由-Ni,Cu）固溶体、硅化物和硼化物组成,Cr3Si晶粒细化且均匀致密;磁场辅助作用下,激光熔覆涂层平均显微硬度达到913HV0.5,为无磁场辅助涂层的1.5 倍,磨损失重仅为无磁场涂层的36%,自腐蚀电位上升了100 mV,腐蚀电流密度降低了70%,耐磨耐蚀性能得到了显著改善。     

金属陶瓷复合涂层的激光熔覆与无裂纹的实现

鉴于传统的激光熔覆金属陶瓷复合涂层技术主要存在2方面不足：其一,熔覆效率低,导致大面积熔覆时成本昂贵;其二,由于激光熔覆本身的特点,即快速加热与快速凝固,在激光熔覆过程中,热应力极易诱导熔覆层开裂。基于此,综述了国内外激光熔覆金属陶瓷复合涂层的研究进展,指出其存在的主要问题,并提出了激光感应复合快速熔覆的新方法,即感应预热基材的同时快速激光熔覆。该方法不仅可使熔覆效率大大提高而且获得了无裂纹的金属陶瓷复合涂层。     

铁基合金激光熔覆层的高温磨损性能

为提高40Cr钢表面耐磨性,采用预置激光熔覆法在40Cr基体表面制备Fe基涂层,利用HT-500摩擦磨损实验机测定干摩擦条件下,基体和熔覆层的摩擦因数随温度变化的规律。利用表面粗糙度轮廓仪测量磨痕的深度和宽度,SEM观察熔覆层以及磨痕的显微组织形貌,使用HV-1000型显微硬度仪检测基体和熔覆层结合部分的硬度。研究结果表明:熔覆层平均显微硬度值达到373.8HV(0.2);显著高于基体硬度198.4HV(0.2)。在干摩擦条件下,随着温度升高,磨损过程逐渐变平缓,平均摩擦因数降低,磨损率增加,耐磨性下降;在350~400 ℃之间,熔覆层磨损性能优于基体。     

铁基合金激光熔覆层的高温磨损性能

 为提高40Cr钢表面耐磨性,采用预置激光熔覆法在40Cr基体表面制备Fe基涂层,利用HT-500摩擦磨损实验机测定干摩擦条件下,基体和熔覆层的摩擦因数随温度变化的规律。利用表面粗糙度轮廓仪测量磨痕的深度和宽度,SEM观察熔覆层以及磨痕的显微组织形貌,使用HV-1000型显微硬度仪检测基体和熔覆层结合部分的硬度。研究结果表明:熔覆层平均显微硬度值达到373.8HV(0.2);显著高于基体硬度198.4HV(0.2)。在干摩擦条件下,随着温度升高,磨损过程逐渐变平缓,平均摩擦因数降低,磨损率增加,耐磨性下降;在350~400 ℃之间,熔覆层磨损性能优于基体。     

铁基合金激光熔覆层高温润滑磨损性能

为提高40Cr合金钢的表面耐磨性,采用预置激光熔覆法在40Cr基体表面制备铁基合金涂层, 利用扫描电镜观察分析熔覆层显微组织形貌,用显微硬度仪测试熔覆层截面显微硬度,用摩擦磨损试验机测定在润滑条件下基体、熔覆层的摩擦系数随温度变化的规律。研究结果表明:熔覆层与基体实现良好冶金结合,熔覆层横截面微观组织呈现平面晶、树枝晶和胞状晶分布;熔覆层硬度值介于617.5~926.6 HV0.2之间,基体硬度介于205.2~278.2 HV0.2之间;在200 ℃以下,熔覆层摩擦系数在磨程中趋于平稳,在0.1附近轻微波动,小于基体平均摩擦系数;当温度超过200 ℃,油膜分解,引发润滑失效,磨损方式向干摩擦转化,磨损机理从微切削磨损主导向粘着磨损、磨粒磨损和氧化磨损复合磨损方式转化。     

稀土CeO_2对镍基纳米Al_2O_3激光熔覆复合涂层组织和性能的影响

采用激光熔覆技术在45钢基体上制备了不同CeO2含量的镍基纳米Al2O3复合涂层,对熔覆层进行了微观组织分析和显微硬度测试。结果表明,随着CeO2含量的增加,熔覆层组织由亚共晶向共晶组织转变;加入1.0%CeO2对镍基纳米Al2O3熔覆层的组织起到明显的细化和净化作用,枝晶生长的方向性减弱,组织趋向均匀,熔覆涂层的显微硬度值比未加稀土的涂层提高了60-95HV0.2。     

斜齿轮激光熔覆Fe基合金组织与性能研究

采用激光熔覆技术在斜齿轮钢表面制备Fe基熔覆层.通过光学显微镜、显微硬度计对熔覆层进行金相组织与显微硬度分析,采用磨损机对熔覆层和基材进行摩擦实验.结果表明:当激光功率为750W,送粉速率为20g/min,扫描速度10mm/s,离焦量为16.4mm时,铁基熔覆层与基体结合界面有明显的白亮带,激光熔覆效果较好,熔覆层的显...     

激光熔覆Al2O3/Fe901复合涂层的强化机制及耐磨性

为提高金属材料表面涂层的耐磨性,采用激光熔覆工艺制备了Al_2O_3增强Fe901金属陶瓷复合涂层,研究了Al_2O_3陶瓷增强相对Fe基熔覆层组织与性能的影响。利用扫描电镜和X射线衍射仪检测了复合涂层的微观组织和物相;采用显微硬度仪和摩擦磨损试验机分析了复合涂层的显微硬度与耐磨性。结果表明:Fe901涂层的组织以柱状枝晶和等轴枝晶为主,添加的Al_2O_3可促使涂层组织转变为均匀的白色网状晶间组织及其包裹的细小黑色晶粒;复合涂层中的Al_2O_3陶瓷颗粒表面发生微熔,与Fe、Cr结合生成Fe3Al及(Al,Fe)4Cr金属间化合物,起到增加Al_2O_3陶瓷颗粒与金属黏结相结合强度的作用;当Al_2O_3陶瓷颗粒的质量分数为10%时,复合涂层的显微硬度较Fe901涂层增加了16.4%,复合涂层的摩擦磨损质量损失较Fe901涂层降低了50%;添加适量的Al_2O_3陶瓷有助于提高涂层的显微硬度及耐磨性。     

电磁搅拌辅助激光熔覆钴基合金涂层的抗热腐蚀性能

在激光熔覆制备钻基合金涂层的过程中引入电磁搅拌,研究了有无磁场辅助时涂层表面在750℃/100 h混合盐条件下的抗热腐蚀性能。研究结果表明,无磁场辅助的涂层的抗热腐蚀性能较差,热腐蚀60 h后涂层内部出现严重的内氧化和内硫化,并出现严重失重现象。经磁场辅助的熔覆层形成了稳定性好的保护性Cr_2 O_3及Co Cr_2 O_4尖晶石氧化膜,有效抑制了腐蚀液中S和Cl~-的向内侵入,在整个腐蚀阶段样品未出现严重开裂剥落现象。电磁搅拌的加入有效细化并均化了熔覆层的显微组织,促进了涂层表面保护性氧化膜的快速形成,阻止了熔盐的扩散,可进一步提高涂层的抗热腐蚀性能。     

不锈钢表面激光熔覆层与喷焊层耐磨性对比研究

本文研究在１Ｃｒ１８Ｎｉ９Ｔｉ基体上采用激光熔覆和离子喷焊二种工艺形成的涂层对耐磨性的影响。使用５ｋＷ横流ＣＯ２激光器对预置在基体上的Ｃｏ基自熔合金粉末进行单道或多道扫描，得到的熔层与等离子焊层对比结果是：激光熔层缺陷率低，成品率高，其结构致密均匀，晶粒细小，成分稀释率更小，对基体热影响小，熔层硬度与强韧性更高。性能试验证明：激光熔层具有更高的抗擦伤磨损和抗冲击滑动高温磨损性能，耐磨性提高了一倍左右。     

激光熔覆层开裂行为的影响因素及控制方法

激光熔覆层开裂是影响覆层质量最主要的因素,特别是厚覆层。选用５ｋＷ 横流ＣＯ２ 激光器对各种不同材料和零件进行厚覆层激光熔覆,实验、检测和使用的效果说明：激光熔覆层开裂主要与激光系统参数、工艺处理条件、覆层材料、基体状况等四个方面有关。分析了熔覆层的开裂行为,并介绍了几种控制方法。     

Composition design and laser cladding of Ni-Zr-Al alloy coating on the magnesium surface

The cluster line criterion was used for optimized design of a Ni-Zr-Al alloy used as coating on the AZ91HP magnesium alloy by laser cladding. Results show that the coating mainly consists of an amorphous, two ternary intermetallic phases with Ni₁₀Zr₇ and Ni₂₁Zr₈ type structures resulting in high hardness, good wear resistance and corrosion resistance. The interface between the clad layer and the substrate has good metallurgical bond.     

Microstructure and wear properties of TiCN/Ti coatings on titanium alloy by laser cladding

Titanium carbide nitride (TiCN) reinforced Ti coating was fabricated on the surface of Ti–6Al–4V alloy by laser cladding method. Microstructure and wear properties at the surface of the coating in atmosphere were investigated. Three zones can be distinguished of the coating: the clad zone (CZ), the heat affected zone (HAZ) and the substrate. The clad zone is composed of TiCN dendrites, TiO₂ and Ti. A metallurgical bonding between the coating and the substrate was obtained. The microhardness and wear resistance of the TiCN/Ti coating are significantly improved. The average hardness of the coating is about 3 to 6 times of that of the substrate. The friction coefficients of the substrate and the coating are 0.48 and 0.34 respectively. The friction coefficient of the Ti–6Al–4V substrate was insensitive to the normal load, while that of the cladded TiCN/Ti coating was very sensitive to the normal load. The wear mass losses of the cladded samples are much lower than that of the substrate whatever the normal load is.     

激光工艺参数对钛合金表面NiCrBSi合金熔覆层组织及硬度的影响

在TC4合金表面进行了激光熔覆NiCrBSi合金涂层的试验 ,利用SEM和XRD等对熔覆层的微观组织进行了分析 ,测试了熔覆层的显微硬度。结果表明 ,激光工艺参数对熔覆层的组织和硬度有极大的影响 ,随稀释率的增加 ,激光熔覆层中形成了TiB2 和TiC等颗粒增强相 ,熔覆层的硬度明显提高。     

Electro-spark alloying using graphite electrode on titanium alloy surface for biomedical applications

In order to improve the biomedical properties of a titanium alloy surface, electro-spark surface alloying was carried out using a graphite electrode in air, in a nitrogen gas atmosphere and in silicone oil. The morphology and microstructure of the strengthened layers were analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The hardness distributions as a function of depth were measured by a micro-hardness tester. Corrosion resistance capacities of the modified layers were evaluated using potentiodynamic polarization measurements and electrochemical impedance spectroscopy (EIS). In addition, wear resistance and corrosive wear properties in a simulated body fluid (SBF) were studied with a pin-on-disk tribometer. Alloyed layers, completely covering the substrate surface and about 40 μm thick mainly composed of the TiC phase and with strong metallurgical bonding and adhesion to the substrate, were obtained. This can markedly improve hardness and wear resistance of the surface layer of the substrate. In comparison to coatings prepared in air and nitrogen gas atmospheres, the coating produced in silicone oil media exhibits a denser and more perfect surface structure. The wear resistance in air and corrosive wear resistance in SBF solution is the best for the coating produced in silicone oil. For instance, the wear rate in air with a GCr15 steel ball counterpart is reduced by a factor of 29 compared with the original titanium alloy and the corrosive wear rate in SBF solution with a corundum ball can decrease by a factor of 13.8. Simultaneously, the effect of electron-spark surface alloying of the titanium alloy surface on biocompatibility and biological activity was also investigated. The electron-spark surface strengthened layer treated in silicone oil shows good biocompatibility and biological activity, and can help cell attachment to the substrate surface.     

Elevated temperature dry sliding wear behavior of nickel-based composite coating on austenitic stainless steel deposited by a novel central hollow laser cladding

In order to improve the high-temperature wear resistance of austenitic stainless steel, a wear resistant composite coating reinforced with hard (Cr,Fe)₇C₃ carbide and toughened by ductile γ-(Ni,Fe)/(Cr,Fe)₇C₃ eutectic matrix was fabricated by a novel central hollow laser cladding technique. The constituent phases and microstructure as well as high-temperature tribological behaviors of the Ni-based coating were investigated, respectively, and the corresponding wear mechanisms were discussed. It has been found that the composite coating exhibits superior wear resistance than substrate either at ambient or high temperatures. The coating shows better sliding wear resistance at 600 °C than 300 °C owing to high-temperature stability of the reinforced carbide and polishing effect as well as formation of continuous lubricious films, which implied it has large potential industrial applications at relatively higher temperatures.     

The surface modified composite layer formation with boron carbide particles on magnesium alloy surfaces through pulse gas tungsten arc treatment

A novel fabrication process of surface modified composite layer by pulse current gas tungsten arc (GTA) surface modification process was used to deposit B₄C particles on the surface of magnesium alloy AZ31. This method is an effective technique in producing a high performance surface modified composite layer. During the pulse current GTA surface modification process, considerable convection can exist in the molten pool due to various driving forces and the pulse current could cause violent stirring in the molten pool, and the large temperature gradient across the boundary between the GTA modified surface and matrix metal resulted in rapid resolidification with high cooling rates in the molten pool, so that the process result notable grain refinement in the GTA surface modified composite layer. The hardness and wear resistance of the GTA surface modified composite layer are superior to that of as-received magnesium alloy AZ31. The hardness values and wear resistance of GTA surface modified composite layer depend on the GTA process parameters and the B₄C particles powder concentration and distribution. The optimum processing parameters for the formation of a homogeneous crack/defect-free and grain refinement microstructure were established.