La2O3对激光熔覆TiC/Ni基复合涂层的影响

利用CO2横流激光器在低碳钢基体表面熔覆含稀土氧化物La2O3的镍基TiC金属陶瓷复合层,研究了不同含量的La2O3对激光熔覆镍基金属陶瓷复合层组织及性能的影响。结果表明,加入适量的稀土氧化物La2O3可有效改善激光熔覆复合层的显微组织,减少复合层中的裂纹、孔洞、夹杂;加速复合层中TiC颗粒的溶解和改善TiC颗粒的形状变化,同时,熔覆复合层的耐磨性和耐蚀性明显提高。     

TA2纯钛表面激光熔覆WC7Co/TC4复合涂层的组织演变特性

选用抗氧化性和韧性良好的WC7Co陶瓷颗粒作为增强相,利用激光熔覆的方法在TA2纯钛表面制备WC7Co/TC4复合耐磨涂层,借助扫描电子显微镜、能谱仪、X射线衍射仪和显微硬度计,分析表征复合涂层显微组织特征、WC7Co陶瓷颗粒界面反应行为以及复合涂层中相的演变规律。结果表明:根据激光熔覆过程中WC7Co颗粒的演变状态,复合涂层中存在2种典型显微组织,分别为未分解WC7Co颗粒强化组织和WC7Co分解后与Ti反应生成的W、TiC和Ti的共晶组织;复合涂层中WC7Co颗粒与TC4基质结合界面形成了2～3μm的反应层,反应生成物主要为W和TiC;复合涂层中的物相主要为Ti固溶体、W单质及TiC、VC、Co_3W_3C、W_2C等化合物。     

浇注过程中制备铸造钢基表面自蔓延高温合成TiC/Fe复合材料的研究

通过在消失模铸件模样需耐磨的部位涂敷一层经压实的SHS粉料，使其在浇注过程中，高温浇注的铁水自动点燃SHS粉料，通过反应生成增强陶瓷相(TiC)。并使铁水铸渗到反应后的SHS陶瓷层中，使陶瓷增强相均匀地分散到熔融的表层金属中，从而获得铸件表面自生复合材料层。经试验研究表明，浇注过程中制备铸造钢基表面自蔓延高温合成TiC／Fe复合材料方法是完全可行的，反应合成的TiC颗粒呈理想孤立球状分布在基体上，复合层厚度可控制在3～15mm；其硬度可达HRC54～59；与基体的相对耐磨性可达6以上；经900℃高温退火后，产生大量细小的二次TiC颗粒。其较优工艺条件为：钢液浇注温度1550～1600℃；SHS粉料预制块组成配比(质量分数)为Ti：C：Al：Fe=4：1：1：2；真空度为0．05MPa。     

La2O3对激光熔覆TiC/Ni基复合涂层的组织和性能的影响

用5kWCO2激光器在A3钢表面激光熔覆添加有La2O3的TiC/Ni基复合涂层，研究了稀土对激光熔覆金属陶瓷复合涂层的组织，耐蚀性和耐磨性的影响。研究结果表明：复合合金粉末中添加0.4%的La2O3能够减少熔覆层的气孔，疏松，使熔覆层的组织致密。熔覆层中TiC分布均匀且细小圆滑，熔覆层的耐蚀性和耐磨性得到提高。     

基于激光熔覆TiC/TiB2的钛合金表面组织及性能研究

在钛合金表面激光熔覆制备TiC/TiB₂复合涂层,分别采用SEM、显微硬度计和摩擦磨损设备分析了TiB₂+15%TiC复合涂层的微观组织和硬度、摩擦磨损性能。实验结果表明:涂层上部组织主要由粗大的TiB₂树枝晶和少量白色颗粒状的TiC/TiB共晶组织组成,涂层中部组织主要由棒状型、细针状型的TiB₂相和小块状的TiC相组成,涂层下部则由树枝型、块状TiB₂相、较大的片状TiC相和少量的小层片状金属间化合物TiAl组成。由测试结果可知,涂层硬度(960HV_0.2)约为基体的(350HV_0.2)的2.7倍。涂层的耐磨性能显著提高,涂层出现较少的剥落、细小磨痕和颗粒碎屑,基体表面主要是犁沟式的磨损。涂层的磨损量为1.132 mg是基体(5.342 mg)的20%。     

微波辅助化学镀铜制备CNTs/Cu复合粉体

碳纳米管(CNTs)表面化学镀是粉末冶金法制备CNTs增强金属基复合材料的重要预处理过程,也是提高其与金属基体界面结合强度的重要途径。本文通过微波辅助化学镀铜法制备CNTs-Cu复合粉体,并对该方法的反应速率和反应效果进行研究。通过碘量法测试镀液中Cu~(2+)的浓度表征反应速率,XRD检测复合粉体中的物相组成,SEM和TEM分别观察复合粉体的微观形貌和结构。实验发现微波辅助化学镀的反应速率是常规化学镀方法的12倍,XRD和电子显微镜分析表明,微波辅助化学镀铜的效果良好,Cu颗粒还原较为充分,CNTs表面附着大量纳米铜颗粒,铜颗粒与CNTs结合紧密,且分布均匀。     

前驱体碳化粉末反应火焰喷涂制备TiC增强金属复合涂层

采用前驱体碳化复合技术制备了Ti-Fe-C和Ti-Ni-C两种体系的反应热喷涂复合粉末,通过氧乙炔火焰喷涂原位合成并沉积了TiC增强Fe基和Ni基复合涂层.利用XRD、SEM和EDS研究了复合粉末、涂层的相组成和组织结构,考察了TiC/Fe、TiC/Ni复合涂层的硬度和耐磨性.结果表明: 复合粉末在喷涂过程中反应充分,可分别生成以Fe和Ni为粘结相的TiC增强涂层;两种涂层都是由TiC颗粒均匀分布的复合强化片层和TiC聚集片层叠加而成,TiC/Fe复合涂层的片层较薄,而TiC/Ni涂层中TiC的聚集片层较少;TiC/Fe涂层的硬度高于TiC/Ni涂层,两者的耐磨性能分别约为Ni60涂层的11倍和6倍.     

碳纤维支撑的钾离子调谐TiC/TiO2层状异质结复合催化剂制备研究

采用原位生长方法制备了一种碳纤维为载体,通过钾离子(K~+)调谐的具有TiC/TiO_2层状异质结的复合催化剂,用FE-SEM、XRD、Raman、XPS和AFM对制备的催化剂进行了表征,并进行了光催化降解污染物罗丹明B试验。研究表明钾离子对异质结的调谐对光催化效率有重要影响。在紫外-可见光催化降解过程中,CFs@TiC/TiO_2对污染物RhB的去除率达到98%。经过3次循环使用后,该复合材料对污染物光催化去除效率仍大于90%,表明能重复稳定使用。K~+协同的原位生长过程经过熔盐体系在碳纤维(CFs)表面生长TiC,并在KOH水溶液中进行水热反应,将部分TiC转化为钛酸钾纳米粒子,随后将钛酸钾纳米颗粒浸泡在稀释的HCl溶液中,将酸中的H~+交换为钛酸钾中的K~+经过热处理和脱水后,纳米颗粒形成片状锐钛矿型TiO_2,最终形成碳纤维支撑的TiC/TiO_2层状异质结的CFs@TiC/TiO_2复合催化剂。钛酸钾纳米晶形成的花状结构具有较大的比表面积,这种结构为制备CFs@TiC/TiO_2复合材料构建了结构特征和催化活性位点。     

扫描速度对激光熔覆TiB_2-TiC/Ni复合涂层组织与性能的影响

在Q235D钢表面激光熔覆制备了TiB_2-TiC/Ni复合涂层,分析了扫描速度对涂层组织及性能的影响。涂层主要由Ni、TiB_2和TiC等物相组成。随着扫描速度的增加,陶瓷相的颗粒逐渐细化。在380mm/min的熔覆速度下制备的涂层,显微硬度为1216HV0.2,在100N的载荷下涂层的摩擦系数和磨损损失明显降低,具有较好的性能。     

微波烧结温度对CNTs/Cu复合材料结构和性能的影响

结合液相混合方法、微波烧结技术和冷轧技术制备碳纳米管增强铜基（carbon nanotubes reinforced copper-matrix,CNTs/Cu）复合材料,研究不同烧结温度对于CNTs/Cu复合材料微观形貌、力学性能及物理性能的影响。结果表明,采用液相混合法制备出粒径为200~500 nm、碳纳米管质量分数为0.5%的CNTs/Cu复合粉体,碳纳米管均匀分散在铜颗粒中,并与之形成良好结合界面。CNTs/Cu复合材料的相对密度、硬度、电导率随着烧结温度的升高先增大后减小,在烧结温度为1000℃时达到最佳。制备的碳纳米管质量分数为0.5%的CNTs/Cu复合材料组织均匀、孔隙数量及尺寸较少,相对密度为95.79%,硬度为HV 80.9,电导率为81.8% IACS。经冷轧处理后,CNTs/Cu复合材料拉伸强度达到218 MPa,延伸率保持37.75%。由此可见,微波烧结技术是一种制备高性能CNTs/Cu复合材料的理想方法。     

TiC 含量对激光熔覆 Fe 基复合涂层组分和性能的影响

采用激光熔覆技术在高锰钢基材上制备了不同 TiC 含量的 Fe 基复合涂层, 研究了 TiC 含量对熔覆层组分 和性能的影响。 试验结果表明, 熔覆层化学组分包含奥氏体、 M7C3 碳化物、 TiC 析出相和未熔 TiC 颗粒。 随着 TiC 含量的增加, 熔覆层硬度逐步增加, 耐磨性能先增加后降低。     

TiC 含量对激光熔覆 TiC 增强双相不锈钢复合涂层性能的影响

采用激光熔覆技术在 40CrNiMo 基材上制备了 TiC 增强双相不锈钢复合熔覆层，熔覆层物相主要由奥氏体、马氏体、M7C3型碳化物和 TiC 组成。其中 M7C3型碳化物主要包括 Fe7C3 、Cr7C3 或者 (Fe、Cr)7C3三种，TiC 按尺寸可分为熔解后析出的微米级 TiC 以及粗大的未熔 TiC 颗粒。析出的 TiC 颗粒为方块状，随着 TiC 添加量增加，呈花瓣状长大。未熔 TiC 颗粒与基材形成了扩散界面，具有很好的界面结合性。当加入 30 wt.% TiC 时，熔覆层具有最好的耐磨性，硬度可达 55.26 HRC，磨损体积为 2.54×10-2mm3 ，耐磨性是基材的 3.37 倍。     

Laser melt injection of austenitic cast iron Ch16D7GKh with titanium

The results of studying the microstructure and microhardness of Ni-resist cast iron ChN16D7GKh after laser melt injection by means of introducing titanium particles into the melt are presented. The treatment was performed using a fiber laser with a beam focused into a spot 0.2 mm in diameter with a radiation power of 1 kW and the motion velocity of the laser beam of 10–40 mm/s. Titanium is dissolved in the cast-iron melt, and TiC particles are formed in the structure upon cooling. The coefficient of using the titanium powder increases as the fusion zone size increases and reaches 50% in the best case. A modified layer has a composite structure with a metallic matrix and a comparatively uniform distribution of titanium carbide particles. The microhardness of the modified zone is 600–700 HV. Its further growth is suppressed by the partial removal of carbon from the melt zone in the composition of red fume evolved in the process. Therefore, the Laves phase (TiFe₂) is formed instead of an increase in the TiC content upon increasing the titanium supply. The experimental data on the regularities of the weight loss caused by the substance removal from the melt zone depending on laser melting parameters are presented.     

气固反应原位生成TiC颗粒增强钛基复合材料

以氢化脱氢钛粉为原料, 经冷等静压成型, 在一定温度下通过CH4和钛粉颗粒间的气固反应在钛粉表面原位生成均匀的TiC颗粒, 采用真空烧结技术制备得到氧含量(体积分数)低于0.2%的TiC颗粒增强钛基复合材料。研究表明, TiC颗粒体积分数比可通过气固反应温度和时间控制, 可获得较高体积分数(> 30%)的TiC颗粒增强钛基复合材料。TiC首先在钛粉颗粒表面形成, 烧结过程中, 钛粉颗粒明显阻碍TiC晶粒长大, 细化TiC晶粒; 同时, 过多的TiC颗粒也阻碍烧结过程中钛的自扩散, 降低烧结相对密度。钛粉压坯在700℃、CH4气氛下发生气固反应(30 min), 再经1300℃烧结后获得的相对密度为98.6%的烧结试样, 试样的综合力学性能较好, 抗拉强度为606 MPa, 延伸率达14.4%, 硬度为HV 442。值得注意的是, 较短时间的气固反应不能够保证压坯内外整体实现原位生成均匀TiC颗粒, 导致烧结试样内外组织的不均性。     

激光功率对 Fe 基复合熔覆层中 TiC 形态及性能的影响

采用激光熔覆技术在高锰钢基材上制备了不同激光功率下的 Fe 基复合熔覆层, 研究了不同激光功率对熔 覆层中 TiC 形态及性能的影响。 试验结果表明, 熔覆层组分包含奥氏体和 TiC, 随着激光功率的增加, TiC 析出 相由单一颗粒状转变为梅花状、 蕨状及颗粒状的组合, 晶粒尺寸增加, 熔覆层硬度和耐磨性逐步提升。     

The Influence of Ni-Coated TiC on Laser-Deposited IN625 Metal Matrix Composites

IN625 Ni-based metal matrix composites (MMCs) components were deposited using Laser Engineered Net-Shaping (LENS) with Ni-coated and uncoated TiC reinforcement particles to provide insight into the influence of interfaces on MMCs. The microstructures and spatial distribution of TiC particles in the deposited MMCs were characterized, and the mechanical responses were investigated. The results demonstrate that the flowability of the mixed powders, the integrity of the interface between the matrix and the TiC particles, the interaction between the laser beam and the TiC ceramic particles, and the mechanical properties of the LENS-deposited MMCs were all effectively improved by using Ni-coated TiC particles.     

Correlation of microstructure with hardness and wear resistance in (TiC,SiC)/stainless steel surface composites fabricated by high-energy electron-beam irradiation

Stainless-steel-based surface composites reinforced with TiC and SiC carbides were fabricated by high-energy electron beam irradiation. Four types of powder/flux mixtures, i.e., TiC, (Ti + C), SiC, and (Ti + SiC) powders with 40 wt. pct of CaF₂ flux, were deposited evenly on an AISI 304 stainless steel substrate, which was then irradiated with an electron beam. TiC agglomerates and pores were found in the surface composite layer fabricated with TiC powders because of insufficient melting of TiC powders. In the composite layer fabricated with Ti and C powders having lower melting points than TiC powders, a number of primary TiC carbides were precipitated while very few TiC agglomerates or pores were formed. This indicated that more effective TiC precipitation was obtained from the melting of Ti and C powders than of TiC powders. A large amount of precipitates such as TiC and Cr₇C₃ improved the hardness, high-temperature hardness, and wear resistance of the surface composite layer two to three times greater than that of the stainless steel substrate. In particular, the surface composite fabricated with SiC powders had the highest volume fraction of Cr₇C₃ distributed along solidification cell boundaries, and thus showed the best hardness, high-temperature hardness, and wear resistance.     

Correlation of microstructure with hardness and wear resistance in (TiC,SiC)/stainless steel surface composites fabricated by high-energy electron-beam irradiation

Stainless-steel-based surface composites reinforced with TiC and SiC carbides were fabricated by high-energy electron beam irradiation. Four types of powder/flux mixtures, i.e., TiC, (Ti+C), SiC, and (Ti+SiC) powders with 40 wt. pct of CaF₂ flux, were deposited evenly on an AISI 304 stainless steel substrate, which was then irradiated with an electron beam. TiC agglomerates and pores were found in the surface composite layer fabricated with TiC powders because of insufficient melting of TiC powders. In the composite layer fabricated with Ti and C powders having lower melting points than TiC powders, a number of primary TiC carbides were precipitated while very few TiC agglomerates or pores were formed. This indicated that more effective TiC precipitation was obtained from the melting of Ti and C powders than of TiC powders. A large amount of precipitates such as TiC and Cr₇C₃ improved the hardness, high-temperature hardness, and wear resistance of the surface composite layer two to three times greater than that of the stainless steel substrate. In particular, the surface composite fabricated with SiC powders had the highest volume fraction of Cr₇C₃ distributed along solidification cell boundaries, and thus showed the best hardness, high-temperature hardness, and wear resistance.     

Hydrogen absorption of incoherent TiC particles in iron from environment at high temperatures

The effect of atmosphere in heat treatment on the hydrogen trapping of incoherent TiC particles in iron has been studied in order to clarify the origin of hydrogen trapped by incoherent TiC particles. The hydrogen trapped by incoherent TiC particles in iron after austenitizing and tempering treatments in air, in a nonprotective argon atmosphere, and in an ultrahigh vacuum (UHV) was identified and quantitatively measured by thermal-desorption spectrometry (TDS). Results showed that incoherent TiC particles in iron do not trap hydrogen at ambient temperature by a cathodic-charging method. It was justified that incoherent TiC particles trap hydrogen during high-temperature heat treatment in nonprotective atmospheres. The amount of hydrogen trapped by incoherent TiC particles decreases with increasing heat-treatment temperature, which is well explained by the equilibrium concentration of hydrogen trapped by incoherent TiC particles in iron under an atmosphere containing water vapor. The hydrogen is supplied through water-vapor oxidation of iron at high temperatures. According to this model, a binding energy between hydrogen and incoherent TiC of 53 kJ/mol was obtained. The energy barrier for hydrogen to jump into incoherent TiC was determined to range from 21 to 35 kJ/mol, which is too high for hydrogen to be trapped by incoherent TiC at low temperatures.     

Correlation of microstructure and abrasive and sliding wear resistance of (TiC,SiC)/Ti-6Al-4V surface composites fabricated by high-energy electron-beam irradiation

This study is concerned with the correlation of microstructure and abrasive and sliding wear resistance of (TiC,SiC)/Ti-6Al-4V surface composites fabricated by high-energy electron-beam irradiation. The mixtures of TiC, SiC, Ti + SiC, or TiC+SiC powders and CaF₂ flux were deposited on a Ti-6Al-4V substrate, and then an electron beam was irradiated on these mixtures. The surface composite layers of 1.2 to 2.1 mm in thickness were homogeneously formed without defects and contained a large amount (30 to 66 vol pct) of hard precipitates such as TiC and Ti₅Si₃ in the martensitic matrix. This microstructural modification, including the formation of hard precipitates in the surface composite layer, improved the hardness and abrasive wear resistance. Particularly in the surface composite fabricated with TiC + SiC powders, the abrasive wear resistance was greatly enhanced to a level 25 times higher than that of the Ti alloy substrate because of the precipitation of 66 vol pct of TiC and Ti₅Si₃ in the hardened martensitic matrix. During the sliding wear process, hard and coarse TiC and Ti₅Si₃ precipitates fell off from the matrix, and their wear debris worked as abrasive particles, thereby reducing the sliding wear resistance. On the other hand, needle-shaped Ti₅Si₃ particles, which did not play a significant role in enhancing abrasive wear resistance, lowered the friction coefficient and, accordingly, decelerated the sliding wear, because they played more of the role of solid lubricants than as abrasive particles after they fell off from the matrix. These findings indicated that high-energy electron-beam irradiation was useful for the development of Ti-based surface composites with improved abrasive and sliding wear resistance, although the abrasive and sliding-wear data should be interpreted by different wear mechanisms.