Microstructure and wear resistance of electro-thermal explosion sprayed stellite coating used for remanufacturing

Electro-thermal explosion directional spraying was used to prepare the stellite coating on substrate of the AISI 1045 steel. The morphologies of cross-section and worn scar, porosity, distribution of elements, micro- hardness and wear resistance of the coating were determined by means of SEM, EDAX, micro-hardness tester and sliding wear tester. Because of the compact construction, good bonding and high hardness, the coating is characterized by good wear resistance. The results show that the mainly failure mode of the stellite coating is micro- plowing.

Effect of electromagnetic stirring on the microstructure and wear behavior of iron-based composite coatings

The effect of electromagnetic stirring on the microstructure and wear behavior of coatings has been investigated. A series of iron-based coatings were fabricated by the plasma-transferred arc cladding process by applying different magnetic field currents. The microstructure and wear resistance of the composite coatings were characterized by scanning electron microscope （SEM）, en- ergy dispersive X-ray analysis （EDAX）, X-ray diffraction （XRD）, and wet sand rubber wheel abrasion tester. The experimental results showed that the microstructure of the coatings was mainly the γ-Fe matrix and （Cr, Fe）7C3 carbide reinforced phase. The coatings were metallurgically bonded to the substrate. With increasing magnetic field current, the amount of the block-like （Cr, Fe）TC3 carbide reinforced phase increased at first, reached a local maximum, and then decreased sharply. When the magnetic field current reached 3 A, the block-like （Cr, Fe）TC3 carbides with high volume fraction were uniformly distributed in the matrix and the coating displayed a high microhardness and an excellent wear resistance under the wear test condition.

Influence of Heat Treatment on Microstructure and Sliding Wear Behavior of Fe-Al/WC Composite Coatings

An experimental study has been carried out to investigate the influence of heat treatment at 300 ℃,450 ℃,550 ℃,650 ℃ and 800 ℃ on the microstructure and sliding wear behavior of Fe Al/WC intermetallic composite coatings produced by high velocity arc spraying (HVAS) and cored wires. The result shows, the main phases in both as sprayed and heat treated Fe Al/WC composite coatings are iron aluminide intermetallics (Fe 3Al+FeAl) and α as well as a little oxide (Al 2O 3) and carbides (WC, W 2C, Fe 2W 2C and Fe 6W 6C). After heat treated at 450-650 ℃, dispersion strengthening of Fe 2W 2C and Fe 6W 6C will lead to a rise in microhardness of the coatings. The microhardness is likely to be the most important factor which influences the sliding wear behavior of the coatings. Increasing the microhardness through heat treatment will improve the sliding wear resistance of the Fe Al/WC composite coatings.

Effect of Microstructure on Wear Behavior of Iron Aluminide Based Coatings

An experimental study has been carried out to investigate the effect of microstructure on sliding wear behavior of Fe-Al coatings and Fe-Al/WC composite coatings produced by high velocity arc spraying (HVAS) and cored wires. After heat treatment at 300°C, 450°C, 550°C, 650°C and 800°C, the microstructure of the coatings will be changed. The changes of microstructure have obvious effects on the microhardness of the coatings, which may be the most important factor influencing the coatings sliding wear behavior. After heat treated at 450°C-650°C, increasing of the amounts of iron aluminides (including Fe3Al and FeAl ) and dispersion strengthening of Fe2\V2C and Fe6W6C will lead to a rise of microhardness of the coatings. Increasing the microhardness through heat treatment would improve the sliding wear resistance of the iron aluminide based coatings coatings.

Preparation and Properties of High Hardness and Oxidation Resisting Coating Using Electric Arc Spray

A coating with high hardness, wear and oxidation resistance was prepared by electric arc spray. The hardness, bonding strength, abrasive wear and values of porosity and oxidation resistance of the coating were investigated. The microstructures and function of Cr3C2 of the coating were analyzed. The results showed surface Rockness Hardness HR30 reached 72.5 and average bond strength reached 49.1Mpa. Also porosity value was less than 2%. In addition, it was found from the comparison between the coating and 45CT coating that, oxidation resistance of the coating was less than that of 45CT, but the abrasive wear of the coating was obvious better than that of 45CT.

Microstructure and properties of thermal-sprayed NiCrWRE coatings

The powders of NiCrW and NiCrWRE alloys were flame sprayed on a medium-carbon steel substrate by thermal spray welding. The micro- structure and tribological behavior of coatings were studied experimentally by means of scanning electron microscopy （SEM）, field emission gun scanning electron microscope （FEGSEM）, and wear tests. The addition of CeO2 modifies the coating morphology from a needle-like structure to a roughly cubic morphology; the refining and purifying effect of rare earth elements makes the microstmcture more compact and finer. Analysis of the worn surfaces reveals that the coatings with CeO2 addition show improved abrasive wear resistance over those without CeO2. By adding CeO2, the hardness of the coatings is significantly increased, and the wear resistance of the coatings is enhanced.

Microstructure characterization and mechanical properties of thermal sprayed Ni-20wt. % Al coating

Thermal sprayed Ni-20wt. % Al coating is fabricated on 6061-T6 aluminum alloy substrates by twin-wire arc spraying （TWAS）. Experimental results present that the average bonding strength is around 53 MPa and the average hardness reaches 325 HV. The Vickers microhardness of NiAl and Ni3Al intermetaUic compounds is larger than that of the substrate, which is beneficial for improving the wear property. Wear mechanism exhibits features of adhesive wear. Friction and wear test results indicate that the wet friction coefficient is higher than the coefficient of dry friction after 200 cycles, and variations of the wet friction coefficient are relatively smaller.

Preparation and characterization of nanostructured Al_2O_3-13wt.%TiO_2 ceramic coatings by plasma spraying

Nanostructured and conventional Al2O3-13wt.%TiO2 ceramic coatings were prepared by plasma spraying with nanostructured agglomerated and conventional powders, respectively. The microstructure and microhardness of the coatings were investigated using scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS）, and microhardness measurement. Meanwhile, the friction and wear behaviors were analyzed and compared using a ball-on-disk tribometer. The results show that the conventional coating has lamellar stacking characteristic and has some pores. However, the nanostructured coating shows a bimodal microstructure, which is composed of both fully melted regions and partially melted regions. According to the microstructural difference, the partially melted regions can be divided into liquid-phase sintered regions （a three-dimensional net or skeleton-like structure： Al2O3-rich submicron particles embedded in the TiO2-rich matrix） and solid-phase sintered regions （remained nanoparticles）. The microstructural characteristics of the liquid-phase sintered region are formed due to the selective melting of TiO2 nanoparticles during plasma spraying. On the other hand, the TiO2 and Al2O3 nanoparticles of the solid-phase sintered regions are all unmelted during plasma spraying. Due to the existence of nanostructured microstructures, the nanostructured coating has a higher microhardness, a lower friction coefficient, and a better wear resistance than the conventional coating.

Influence of oxides on high velocity arc sprayed Fe-Al/Cr_3C_2 composite coatings

Fe-Al/Cr3C2 coatings were sprayed on low steel by high velocity arc spraying（HVAS） technology. The influences of oxides on erosion, corrosion and wear behavior for high velocity arc sprayed Fe-Al/Cr3C2 coatings were studied. The results show that HVAS-sprayed Fe-Al/Cr3C2 coatings have good erosion, heat corrosion and wear resistance. The erosion resistance improves with the increase of the temperature. On one hand, the ferrous oxides are incompact, so they peel off the surface of the coatings easily during the high temperature erosion. On the other hand, compact Al2O3 films on the surface can protect the coatings.

PTA clad (Cr,Fe)_7C_3/γ-Fe in situ ceramal composite coating

A wear-resistant （Cr, Fe）7C3/γ-Fe in situ ceramal composite coating was fabricated on the substrate of 0.45wt%C carbon steel by a plasma-transferred arc cladding process using the Fe-Cr-C elemental powder blends. The microstructure, microhardness, and dry-sliding wear resistance of the coating were evaluated. The results indicate that the microstructure of the coating, which was composed of （Cr, Fe）7C3 primary phase uniformly distributed in the γ-Fe, and the （Cr, Fe）7C3 eutectic matrix was metallurgically bonded to the 0.45wt%C carbon steel substrate. From substrate to coating, the microstructure of the coating exhibited an evident epitaxial growth character. The coating, indehiscent and tack-free, had high hardness and appropriate gradient. It had excellent wear resistance under the dry sliding wear test condition.

异种丝材电弧喷涂ZnNiAl涂层的组织与耐磨耐蚀性能

采用双枪同时电弧喷涂Ni95Al5丝材与Zn85Al15丝材在Q235钢基材表面制备了Zn NiAl涂层。通过X射线衍射仪(XRD)、扫描电镜(SEM)和能谱仪(EDS)表征了涂层的物相、表面形貌以及成分,并通过硬度试验、摩擦磨损试验和电化学试验研究了涂层的耐磨性能和耐腐蚀性能。结果表明:Zn NiAl涂层由Zn相、Ni(Al)固溶体相以及Al相等多相组织组成,且存在少量的氧化物颗粒与微孔洞;其磨损形貌呈现出黏着磨损与磨粒磨损复合特征,涂层中锌、铝元素的钝化作用以及镍元素加入可降低涂层腐蚀速率,实现耐磨、耐蚀性能提升。

High Velocity Electric Arc Sprayed Fe-Al-Nb-B Composite Coating and Its Wear Behavior

A type of Fe-Al-Nb-B cored wire was designed and the coating was prepared using a robot-based electric wire arc spraying process. The Fe-Al binary cored wire and coating were also prepared as comparison. The phase composition and structure of the coatings were investigated using X-ray diffraction （XRD）, scanning electron microscopy （SEM） coupled with energy dispersive X-ray spectroscopy （EDS） and transmission electron microscopy （TEM）. The coating tribological properties were evaluated with the micromotion wear tester under different conditions. The results show that, although typical lamellar structure was performed for both the arc sprayed Fe-Al-Nb-B coating and Fe-Al coating, the structure composition, mechanical and wear properties of the former are quite different from those of latter. The Fe-Al-Nb-B coating is a typical composite coating, which is distributed inhomogeneously with α-Fe crystalline, FeAl and Fe3Al intermetallics, amorphous and nanocrystallines as well as locally existed oxide phases. As a result, the mircrohardness and wear resistance of the Fe-Al-Nb-B composite coating increased significantly. Finally the mechanism of the coating wear resistant behavior was discussed based on the experimental results such as friction coefficient, two dimensional and three dimensional worn surface profiles.

La(NO_(3))_(3)掺杂对TC4微弧氧化/水热复合涂层显微结构和耐磨性的影响

作为生物医用材料,TC4钛合金在骨组织再修复领域中临床使用量很大,中国每年的消耗量约为百万件以上。但TC4钛合金耐磨性低、生物活性差等问题严重制约其工程应用领域的扩展。为此,采用微弧氧化/水热合成复合技术在TC4表面制备微弧氧化/水热复合涂层,研究水热合成液中La(NO_(3))_(3)掺杂量对TC4钛合金微弧氧化/水热涂层的相组成、微观形貌、显微硬度、耐磨性等参数的影响作用。利用XRD、SEM、显微硬度计、摩擦磨损试验机等手段对TC4钛合金微弧氧化/水热涂层进行表征。研究结果表明:TC4钛合金微弧氧化/水热涂层相组成主要由锐钛矿型TiO_(2)和羟基磷灰石组成。经过水热处理后合成液中La^(3+)进入到复合涂层中,参与涂层反应。随着La(NO_(3))3掺杂量增加,获得的复合涂层中羟基磷灰石相含量先增加后降低。当La(NO_(3))_(3)掺杂量超过24 mmol/L时,涂层表面变得更为光滑。TC4钛合金微弧氧化/水热涂层的显微硬度先降低后增加,且其摩擦系数先增大后减小。当La(NO_(3))_(3)掺杂量达到24 mmol/L时,涂层的显微硬度达到最小值,约为271.8 HV9.8 N;涂层摩擦系数达到最大值,约为0.8~0.9。

冷喷涂制备CuZn35涂层结构及耐摩擦磨损性能

目的采用高压冷喷涂技术制备低氧化、致密、耐摩擦磨损的CuZn35涂层,并探究加速气体温度对CuZn35涂层性能的影响。方法利用高压冷喷涂技术在铝板上沉积CuZn35涂层,探究加速气体温度对冷喷涂CuZn35涂层微观结构及耐摩擦磨损性能的影响。在载荷为2 N时,在旋转式摩擦磨损试验仪上进行试验,对比铸态CuZn35材料的耐磨性能,评估在压力为5 MPa,加速气体温度为400、600、800℃条件下冷喷涂制备的CuZn35涂层的耐磨性能。通过光学显微镜(OM)、扫描电镜(SEM)、三维轮廓仪(3D Profiler)对涂层的微观结构和磨损表面形貌进行分析。结果当冷喷涂加速气体温度从400℃升至800℃时,CuZn35涂层内部颗粒的变形量不断增大,颗粒之间形成了较好的结合,孔隙率从2.67%降至0.5%以下,硬度从200HV0.3升至242HV0.3,涂层磨损率从3.67 mm^(3)/(N·mm)降至1.80 mm^(3)/(N·mm)。在温度为800℃条件下制备的CuZn35涂层表现出最优的耐摩擦磨损性能,在磨损过程中涂层材料未发生明显的块状脱落现象,仅其表面有轻微磨痕,涂层的磨损率较低,与铸态CuZn35材料相近。结论高压冷喷涂技术可获得与铸态CuZn35材料耐磨性能相近的CuZn35涂层。随着冷喷涂加速气体温度的升高,CuZn35涂层的孔隙、微裂纹等缺陷显著减少,涂层颗粒间的结合性增强,涂层的硬度逐渐增大。在摩擦磨损实验中,涂层的耐磨性能随着制备过程中加速气体温度的升高显著增强。

冷喷涂制备铝基涂层研究进展及应用现状分析

系统介绍了近年来冷喷涂制备铝基涂层的现状,总结了Al-Ni、铝青铜、高铝青铜、Al-Al_(2)O_(3)、Al-Fe、铝基非晶涂层这几种铝基涂层体系在冷喷涂制备中所采用的工艺,对涂层的微观结构、力学性能以及耐腐蚀、耐磨损性能等进行了阐述,并对冷喷涂技术制备铝基涂层的研究发展和应用方向进行了展望。

氩弧熔覆Al_(x)CoCrFeCuNi高熵合金涂层组织与耐磨性

目的利用氩弧熔覆技术在45钢表面制备出AlCrFeCoCuNi高熵合金涂层,改善其耐磨性能。方法采用机械球磨方式将Al、Cr、Fe、Co、Cu、Ni粉均匀混合,预涂敷在45钢表面,利用氩弧熔覆技术制备出不同Al物质的量之比的高熵合金涂层。采用X射线衍射仪、扫描电子显微镜及能谱分析仪分析涂层的物相及显微组织,利用显微硬度仪测试涂层表面及截面的显微硬度。采用摩擦磨损试验机测试涂层的摩擦系数及磨损率,分析涂层的耐磨性能。结果Al_(x)CrFeCoCuNi高熵合金涂层物相主要包括面心立方(FCC)相和体心立方(BCC)相,当Al物质的量之比小于0.5时,涂层由FCC相构成;当Al物质的量之比为1.0~2.0时,涂层由BCC+FCC相构成;当Al物质的量之比达到2.5时,涂层仅存在BCC相。Al_(x)CrFeCoCuNi高熵合金涂层组织由等轴晶、柱状晶及白色的晶界构成,且较为致密。Al物质的量之比的增加使得涂层的显微硬度提升,当Al物质的量之比为2.5时,涂层最高硬度为710 HV0.5。在相同磨损条件下,Al_(x)CrFeCoCuNi高熵合金涂层的摩擦系数及磨损率随着Al物质的量之比的增加逐渐减小。结论与45钢基体对比,Al_(2.5)CrFeCoCuNi高熵合金涂层的耐磨性提高了9倍,耐磨性得到显著提高。

冷喷涂Al6061/SiC复合涂层的制备及性能研究

为提高铝合金在实际应用过程中的服役寿命和可靠性,常需在表面制备涂层以提高其耐磨及耐腐蚀性能。采用不同种类的SiC粉末,利用冷喷涂工艺在Al7075合金基体表面制备了Al6061/SiC复合涂层,并探究了SiC含量和粒径对涂层微观组织、磨损性能及耐腐蚀性能的影响。结果表明:添加不同种类SiC颗粒所制备的Al6061/SiC复合涂层均致密;相同SiC比例下,黑SiC所制备的涂层硬质颗粒含量最高,在10 N载荷下磨损率最低,但涂层的耐腐蚀性能相近;Al6061与黑SiC以不同质量比所制备的涂层中,涂层磨损率随着SiC比例的增加呈现先减小后增加的变化趋势,比例为3∶7的涂层硬质颗粒含量最高(57.5%),磨损率最低[1.7876×10^(-4)mm^(3)/(N·m)],但其耐腐蚀性能不如其余比例的涂层;将黑SiC筛分得到15~30μm和>30μm 2种粉末,将Al6061分别与这2种粉末按照3∶7质量比混合,所制备的涂层磨损性能均不如原始粉末,但耐腐蚀性能均优于原始粉末,其中混合15~30μm黑SiC所制备涂层的腐蚀电流密度为9.59×10^(-5)A/cm^(2)。

氮弧熔覆TiCN/Fe金属陶瓷涂层对农业刀具耐磨性的影响

针对农业刀具易磨损、失效频繁的现状,采用TXⅡ500型TIG焊机,以工业纯氮作为反应气体和保护气体,利用反应氮弧熔覆技术在表面预涂工业钛粉和石墨粉的Q235试件上成功制备了TiCN/Fe金属陶瓷复合涂层。利用扫描电镜、XRD射线衍射仪、显微硬度计着重分析了熔覆速度对涂层形貌、涂层物相、涂层显微硬度的影响,并与农业刀具进行了耐磨对比试验。结果表明:熔覆速度较小时涂层表面成形良好,但涂层中TiCN含量低、涂层硬度小;随着熔覆速度的增加,涂层表面成形变差,但涂层硬度增大。涂层近表层显微硬度最高可达HV0.51089,约是Q235硬度的3倍多,与农业刀具常用材料65Mn相比,磨损量仅为65Mn的1/2,涂层有较好的耐磨性。

高速电弧喷涂技术在装备维修与再制造工程领域的研究应用现状

高速电弧喷涂技术是一种优质、高效、低成本的再制造工程关键技术,综述了高速电弧喷涂技术的发展,及其分别在汽车发动机再制造、装备钢结构件防腐、火电厂锅炉管道受热面防护领域的研究应用现状,并展望了高速电弧喷涂技术在维修与再制造工程中的发展趋势。

高速电弧喷涂Fe-Al金属间化合物涂层

采用粉芯丝材和高速电弧喷涂技术(HVAS)制备了Fe Al金属间化合物涂层,并研究了涂层的显微组织和室温至650℃的滑动摩擦磨损性能。结果表明:Fe Al涂层的平均成分为Fe 20.0Al 14.1O(摩尔分数,%),主要相是Fe3Al,FeAl,α Fe,Al2O3及少量Al;涂层具有较高的结合强度和硬度、较低的孔隙率及较高的高温耐磨性;高温下磨损面形成了大面积的氧化物保护层,降低了涂层的摩擦因数,而剥层磨损是涂层的主要磨损机制。涂层中Fe3Al和FeAl金属间化合物相较高的高温强度和硬度能有效地阻碍裂纹的产生、扩展及扁平颗粒的断裂,从而使Fe Al涂层表现出优异的高温耐磨性。