微纳米WC-10Co4Cr涂层在NaCl介质中的抗泥沙冲蚀性能研究

采用超音速火焰喷涂(HVOF)工艺制备了微纳米、纳米和普通结构WC-10Co4Cr金属陶瓷涂层,测量了涂层的显微硬度、孔隙率和开裂韧性,分析了三种WC-10Co4Cr涂层在3.5wt%NaCl溶液中的腐蚀电位和腐蚀电流密度,研究了喷涂层在NaCl介质中的抗泥沙冲蚀性能,并探讨了涂层在NaCl介质中的泥沙冲蚀机理。结果表明:微纳米WC-10Co4Cr涂层具有最优异的电化学性能;相比于纳米、微米涂层,微纳米涂层的抗泥沙冲蚀磨损性能分别提高了38%和78%。微纳米WC-10Co4Cr涂层致密的组织结构、高显微硬度(1126HV_(0.3))和高开裂韧性(4.66MPa·m~(1/2))有效减弱了泥沙冲蚀过程中的机械冲刷作用和电化学腐蚀作用。     

铜结晶器HVAF法喷涂WC-Cr3C2-Ni的试验研究

为了提高结晶器铜板的抗磨损能力,采用空气助燃超音速火焰喷涂法(HVAF)在铜板表面喷涂WC-Cr_3C_2-Ni硬质合金涂层.性能测试结果表明,使用HVAF法制备的WC-Cr_3C_2-Ni涂层脱碳较轻,孔隙率低;具有高硬度、高耐磨性的力学性能,涂层平均显微硬度能够达到1 337HV_(0.3);涂层热稳定性较好,平均导热系数为292.11 W/(m·K).与目前使用的WC-17Co涂层相比,综合性能更佳.现场生产试验结果证实,WC-Cr_3C_2-Ni涂层的效果优于WC-17Co涂层.     

超音速火焰喷涂WC-12Co涂层抗磨粒磨损性能研究

采用超音速火焰（HVOF）喷涂工艺在316L不锈钢基体上制备了WC-12Co涂层,测试了涂层的结合强度、显微硬度、气孔率以及抗磨粒磨损性能。并利用XRD对喷涂粉末及涂层进行了相结构分析,用扫描电子显微镜对喷涂粉末、磨粒磨损前后的涂层表面形貌进行了观察。结果表明：在喷涂过程中,仅有很少量的WC粒子发生氧化脱碳。涂层的结合强度和显微硬度高,组织结构致密。在相同的实验条件下,316L的磨粒磨损量是WC-12Co涂层的95倍,这表明HVOF制备的WC-12Co涂层具有优异的抗磨粒磨损性能。     

超音速火焰喷涂WC-12Co涂层抗磨粒磨损性能研究

采用超音速火焰(HVOF)喷涂工艺在316L不锈钢基体上制备了WC-12Co涂层,测试了涂层的结合强度、显微硬度、气孔率以及抗磨粒磨损性能。并利用XRD对喷涂粉末及涂层进行了相结构分析,用扫描电子显微镜对喷涂粉末、磨粒磨损前后的涂层表面形貌进行了观察。结果表明:在喷涂过程中,仅有很少量的WC粒子发生氧化脱碳。涂层的结合强度和显微硬度高,组织结构致密。在相同的实验条件下,316L的磨粒磨损量是WC-12Co涂层的95倍,这表明HVOF制备的WC-12Co涂层具有优异的抗磨粒磨损性能。     

HVOF喷涂超细结构WC-12Co涂层磨粒磨损性能

以喷雾转换法制备的球壳形WC-12Co复合粉为原料,采用超音速火焰喷涂(HVOF)在45~#钢上制备超细结构WC-12Co涂层,并测试涂层的显微硬度、开裂韧性。利用XRD、SEM和磨损试验机分析涂层物相组成、微观结构和耐磨损性能。结果表明:多孔球壳形WC-12Co复合粉在HVOF喷涂过程中发生了中度脱碳,涂层中不仅含有WC、W_2C相,还有少量W相;涂层微观结构致密,组织呈岩层状,截面平均显微硬度HV_(0.3)为1 205.5、平均开裂韧性为4.96 MPa·m~(1/2);磨损过程中,粘结相被SiO_2犁削出非连续状槽沟,WC晶粒剥离或裂解出的细小WC晶粒成为新的磨粒,对粗大晶粒产生磨削或积于裂纹处加剧开裂。     

粉末粒度对超音速火焰喷涂WC-10Co4Cr涂层性能的影响

采用超音速火焰喷涂工艺对两种不同粒度范围的WC-10Co4Cr粉末进行了涂层制备,分析了粉末粒度对喷涂涂层的微观组织、相结构、磨粒磨损及电化学腐蚀性能的影响。结果表明,粉末粒度较小时沉积的涂层结构致密、孔隙率低,具有较好的抗磨粒磨损性能和耐腐蚀性能。通过进一步粉末粒度的优选,获得了显微硬度大于1300HV0.3、孔隙率小于0.1%、结合强度90MPa、中性盐雾性能超过500h的WC-10Co4Cr耐磨防腐涂层。     

HVOF 制备的微纳米 WC-CoCr 涂层抗空蚀性能及数学模型

采用不同的超音速火焰喷涂(HVOF)工艺制备了6种微纳米WC-10Co4Cr金属陶瓷涂层,测量了涂层的显微硬度、孔隙率及断裂韧性,采用超声振动空蚀装置研究了涂层在淡水介质中的抗空蚀性能,探讨了涂层显微硬度、孔隙率及断裂韧性与空蚀量的规律和影响程度。结果表明:液体燃料HVOF喷涂的WC-10Co4Cr涂层的抗空蚀性能明显优于气体燃料HVOF喷涂的WC-10Co4Cr涂层;喷涂工艺相同时,多峰WC-10Co4Cr涂层表现出最优良的抗空蚀性能,纳米WC-10Co4Cr涂层抗空蚀性能最差;涂层断裂韧性对HVOF喷涂的WC-10Co4Cr涂层的抗空蚀性能的影响程度最大。     

超音速火焰喷涂Cr_3C_2-25%NiCr涂层的滑动摩擦磨损性能研究

采用超音速火焰喷涂工艺制备了Cr_3C_2-25%NiCr陶瓷,对涂层的组织结构、显微硬度及在滑动摩擦条件下的失重进行了分析,得出了涂层摩擦因数与时间的关系,对涂层的滑动摩擦磨损机理进行了分析。结果表明Cr_3C_2-25%NiCr涂层致密,孔隙率为0.96%,涂层截面的显微硬度平均值HV_(0.3)为867。涂层稳定的摩擦因数为0.1。初始阶段涂层的磨损主要是磨屑对涂层的磨粒磨损作用,摩擦稳定后涂层的磨损主要是由于相对运动面的磨削作用。     

超音速火焰喷涂WC-12Co涂层工艺优化

为了进一步优化JP5000超音速火焰喷涂WC-12Co涂层的制备工艺,本文采用四因素三水平正交实验方法研究了喷涂距离、煤油流量、氧气流量和送粉量等四个主要工艺参数对WC-12Co涂层孔隙率和显微硬度的影响。结果表明:煤油流量是影响涂层孔隙率和显微硬度的最显著因素,氧气流量与喷涂距离次之,送粉量的影响较小;本次试验得到的优化工艺参数为喷涂距离380mm、煤油流量22.5L/h、氧气流量2050SCFH、送粉量5.5r/min。在此工艺参数下制备的WC-12Co涂层,其孔隙率为0.33%,显微硬度为1392HV300。     

爆炸喷涂WC-14Co涂层工艺优化

采用四因素三水平正交试验方法对爆炸喷涂WC-14Co涂层工艺进行了优化。主要从氧燃比、填枪比、喷涂距离和送粉量四个工艺参数入手,探究了其对涂层孔隙率和显微硬度的影响。结果表明:对WC-14Co涂层来说,填枪比是对孔隙率和显微硬度影响最大的因素。优化后工艺参数为氧燃比1.014、填枪比70%、喷涂距离200mm、送粉量7.8g/min。在此工艺条件下制备的涂层孔隙率为0.12%,显微硬度为1120HV_(0.3)。     

超音速等离子喷涂纳米防污陶瓷涂层研究

以NiCr合金为底层,含防污成分的纳米Al_2O_3-13%TiO_2为面层,采用超音速等离子喷涂方法制备纳米防污陶瓷涂层。研究了不同工艺对涂层截面形貌、孔隙率、显微硬度及结合强度的影响,探讨了涂层的防污性能,获得了较优的喷涂工艺参数:Ar流量3.6～3.8 m~3/h,H_2流量0.4 m~3/h,电流400～420A,电压150V,喷距100mm,送粉量30g/min。采用较优超音速等离子喷涂工艺制备的纳米防污陶瓷涂层孔隙率可达0.8%,HV_(0.3)≥987,结合强度≥35.15 MPa,并且抗海生物附着性能优良。     

HVAF喷涂超细WC-10Co-4Cr粉末涂层的耐腐蚀性研究

对比研究超细和常规粒度WC-10Co4Cr粉末喷涂制备涂层的性能,根据显微形貌、力学性能与电化学特性比较两种涂层的耐腐蚀性并分析机理。在304不锈钢基体上,利用空气助燃高速(High Velocity Air Fuel, HVAF)热喷涂技术制备WC-10Co-4Cr涂层。采用SEM和XRD分析了涂层的物相组成和显微形貌,采用维氏硬度仪和万能拉伸试验机分别测试了涂层的显微硬度与结合强度以表征力学性能,在质量分数为3.5%的NaCl溶液中对涂层进行电化学分析。结果表明：两种WC-10Co-4Cr粉末涂层均具有优异的耐腐蚀性能,超细粉末涂层自腐蚀电位(-0.199 V)高于常规粉末粒径涂层(-0.267 V);超细粉末粒径涂层腐蚀电流密度(1.996×10^-7 A/cm2)小于常规粉末粒径涂层(3.123×10^-6 A/cm²),对基体能起到良好的保护作用。超细粉末与常规粉末WC-10Co-4Cr涂层电位腐蚀的机理主要是WC与粘结相的电偶腐蚀、Cl-对涂层表面钝化膜的破坏引起的孔蚀,腐蚀机理基本一致,主要差异在于,超细粉末涂...     

电弧喷涂含陶瓷颗粒铝基复合涂层的微结构和性能

采用5052半硬铝带分别包覆Al_2O_3、SiC、B_4C、TiC陶瓷颗粒制备的粉芯丝材进行电弧喷涂试验,制备了含陶瓷颗粒的铝基复合涂层。利用光学显微镜、XRD分析了涂层的微观组织和相结构,测试了复合涂层的显微硬度、耐磨性及耐腐蚀性。研究结果表明,制备的铝基复合涂层中含有一定数量的未熔陶瓷颗粒,涂层较为致密,无明显缺陷。含陶瓷铝基涂层的物相主要由Al和所添加的陶瓷相构成,其中在含B_4C陶瓷涂层中还存在Al_3BC、Al_4C_3和AlB_2等新相。陶瓷颗粒的加入有利于提高铝基复合涂层的显微硬度,其中B_4C的加入使涂层中基体相显微硬度提高了1.5倍,这是由于B_4C陶瓷和Al反应生成Al_3BC、Al_4C_3和AlB_2硬质相。复合涂层的耐磨性均优于纯铝涂层,摩擦磨损的形式主要为粘着磨损。动电位极化腐蚀试验表明,含SiC和TiC陶瓷涂层具有较低的腐蚀电流,耐蚀性较好,含SiC陶瓷的复合涂层出现了明显的钝化现象。     

Study on Effect of Process Variables on Distributed Compositional Characteristics in Metallurgically and Mechanically Bonded Claddings

In surface modification applications, cermets such as Cr₃C₂–NiCr are used to enhance the wear resistance of the substrate. Friction surfaced cladding is a recently developed solid-state surface modification process in which the deposition of the clad layer is accomplished below it’s melting temperature, so that degradation of the substrate is minimized. The present investigation discusses the friction surfaced cladding of Cr₃C₂–NiCr using consumable die steel rod. It was observed from the micrographs, that with the suitable combination of tool plunging rate (plunging speed), tool rotational speed and traverse rate, successful cladding of Cr₃C₂–NiCr was achieved. A plan of full factorial experiment was followed for determining the process variables for the successful deposition of Cr₃C₂–NiCr clad layer with the substrate. A mathematical model was developed to predict the composite clad dimensions and microhardness with respect to the process variables. Depending upon the process parameter, it was observed that the hardness of the clad and clad geometrical feature varied. The microstructural analysis exhibited sound and uniform bonding of clad layer to the substrate and near uniform distribution of Cr₃C₂–NiCr. Desirability based multi-response optimization procedure was followed to arrive at optimized Cr₃C₂–NiCr clad.     

镍铬?莫来石复合陶瓷涂层热障及抗热震性能的研究

使用球磨法混制了五组不同比例的镍铬?莫来石复合粉末,利用超音速等离子喷涂技术在45钢基材表面制备相应的镍铬?莫来石复合陶瓷涂层,测定涂层导的热系数和抗热震性能,采用扫描电子显微镜观察涂层表面、截面显微形貌,利用能谱仪分析涂层特征区的组织成分,通过X射线衍射分析涂层组织结构。结果表明,镍铬?莫来石复合涂层以镍铬固溶体为基体,其上均匀分布着莫来石颗粒,莫来石与基体之间形成了扩散相,提高了莫来石与基体之间的润湿性,使莫来石被基体牢固包覆;莫来石颗粒的加入强化了基体,在莫来石体积分数38%～75%范围内,随着莫来石含量的增加,涂层强韧性增加,抗热震性提高,热导率降低。     

Microstructure and Wear Behavior of Laser-Aided Direct Metal Deposited Co-285 and Co-285?+?WC Coatings

The laser-aided direct metal deposition technique was used to form Co-285 superalloy (A) and Co-285 + 30 wt pct WC (B) wear-resistant coatings on 1018 mild steel. Microstructure, element distribution, phases, microhardness distribution, and wear properties of the two coatings were investigated using scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX) spectrometry, scanning transmission electron microscopy (TEM), X-ray diffractometry (XRD), microhardness testing, and wear testing. Results indicate that both of the coatings had dense structures, as well as a metallurgical bonding with the substrate. In addition, coating B had microcracks and randomly distributed undissolved WC particles in it. Coating A was composed of α-Co dendrites, Co₃W precipitates, and eutectics, while coating B was composed of undissolved WC, Co-rich dendrites, eutectics, and the W-rich third phases with various shapes. Crack behavior in coating B was also discussed. The average microhardness of the matrix in coating B was 751 HV_0.5, which was almost 1.8 times that of coating A (420 HV_0.5). Wear results indicate that the wear resistance of coating B was improved by 6.8 times compared with that of coating A. The improvement in wear resistance is believed to be partially due to the undissolved WC and the formation of large numbers of carbides in the matrix working as wear-resistant phases and partially due to the good bonding between the hard phases and the tough matrix.     

NiCr过渡层对高速火焰喷涂WC-Co涂层摩擦磨损性能及疲劳磨损性能的影响

WC-Co涂层作为一种性能优异的涂层,逐渐被应用于轧辊的表面防护,目前大量实验研究的有热喷涂、激光熔覆制备WC-Co涂层。本文提出用高速火焰喷涂(HVOF)在常用轧辊材料Q235钢表面制备WC-Co涂层,同时在WC-Co涂层和基体之间加入NiCr过渡层。利用SEM、XRD、摩擦磨损测试、疲劳磨损测试等测试方法,对涂层形貌结构以及各项性能与无过渡层涂层进行对比研究。结果表明,加入NiCr过渡层后,WC-12Co+NiCr、WC-10Co-4Cr+NiCr涂层硬度分别为1059.64 HV_0.3、1016.96 HV_0.3,比WC-12Co涂层(960.01 HV_0.3)、WC-10Co-4Cr涂层(1012.20 HV_0.3)更高。WC-12Co+NiCr涂层的磨损率(5.19×10^-15 m³·(N·m)^-1)远低于WC-12Co涂层(6.59×10^-15 m³·(N·m)^-1     

Influence of Fracture Toughness and Microhardness on the Erosive Wear of Cermet Coatings Deposited by Thermal Spray

An evaluation of the relationship between the microhardness and fracture toughness with resistance to erosive wear of WC10Co4Cr, WC-12Co, and Cr3C2-25NiCr coatings was conducted. Powder and flexible cored wire feedstock materials were applied by high-velocity oxygen fuel (HVOF) and flame spray (FS), respectively. The erosive wear mechanism prevailing in the coatings was found to be brittle, which also explains the higher erosion rate for the experimental condition using the particle impact angle of 90 deg and impact velocity of 9.33 m/s. The best wear performance was for the coatings applied by HVOF that attains 1.83 mm³/kg for the 90 deg/3.61 m/s test condition. The coating obtained with the WC-10Co4Cr material using the FSFC method showed tungsten carbide decarburization, justifying its poor mechanical properties and poor performance in the erosive wear test. Flame-sprayed flexicords proved to be a promising alternative to HVOF in obtaining coatings with low porosity and acceptable mechanical properties, especially in applications where the use of the HVOF technique is inadequate because of inaccessibility or excessively high cost. Values of K _c for the coatings obtained by HVOF (7.35 to 10.83 MPa.m^1/2) were between two and three times greater than the values obtained for the coatings resulting from FSFC (2.39 to 3.59 MPa.m^1/2), in a similar manner as with the microhardness.

     

WC颗粒尺寸对超音速火焰喷涂WC–10Co4Cr涂层组织及力学性能的影响

采用超音速火焰喷涂技术(high velocity oxygen-fuel, HVOF)制备了纳米结构、亚微米结构及常规结构的WC-10Co4Cr涂层, 研究了沉积过程中颗粒尺寸对WC脱碳行为的作用, 分析了WC颗粒尺寸对复合涂层微观组织、硬度、断裂韧性及界面结合强度的影响。结果表明: 随着WC颗粒尺寸的增大, WC脱碳率和涂层孔隙率先增大后减小, 而涂层硬度和断裂韧性先减小后增大, 界面结合强逐渐降低。在100 g压痕载荷下, 亚微米和常规结构涂层硬度的Weibull分布呈双峰特征, 而在300 g压痕载荷下, 3种结构涂层硬度的Weibull分布均呈单峰特征, 这是3种结构涂层的WC脱碳程度、层间结合力和孔隙率综合作用结果。WC-10Co4Cr纳米结构涂层呈现出低脱碳率、高硬度、高界面结合强度和适中断裂韧性的优异综合性能。     

A comparative Study on the Wear Behavior of Al2O3 and SiC Coated Ti-6Al-4V Alloy Developed Using Plasma Spraying Technique

This paper reports the wear characteristics of the ceramic coatings made with Al₂O₃ and also with SiC which were performed using atmospheric plasma spraying technique on the Ti-6Al-4V biomedical alloy with the aim of improving their tribological behavior. The wear behavior of the coatings was evaluated using reciprocatory wear tester with coated substrate as the flat and alumina ball as a friction partner in simulated body fluid (Hank’s solution) environment. The microstructure and phase composition of the ceramic powders and as-sprayed coatings have been characterized using scanning electron microscope and X-ray diffractometer. Porosity, microhardness, adhesion strength and roughness of the coatings were measured as they have a bearing on wear and friction behavior. The results indicate that plasma sprayed Al₂O₃ coating exhibits higher wear resistance compared to that of plasma sprayed SiC coating. The higher wear resistance of Al₂O₃ coating is attributed to the improved melting and spreading of the alumina particles onto the substrate yielding increasingly bonded splats, resulting in compact and dense microstructure with lower porosity and higher microhardness.