Fabrication of in-situ synthesized ceramic reinforced Ni-based alloy composite coatings by reactive braze coating processing

In-situ synthesized ceramic such as TiC,Cr7C3 and Cr5B3 reinforced Ni-based alloy composite coating was fabricated on the surface of mild steel substrate by reactive braze coating processing with colloidal graphite,Cr,Ni,ferro-boron,Si and titanium powders as the raw materials at low temperature of 1000℃,and a new kind of coating materials was developed.By means of SEM,EDS,XRD and surface hardness tester,the microstructures,phases,hardness and wear-resistance of the coating were analyzed,respectively.The results revealed that the coating was mainly composed of the ceramic in-situ synthesized reinforcement phases of TiC,Cr7C3 and Cr5B3 and the binder phases in-situ synthesized of Ni31Si12 and(Ni,Fe)solid solution;The ceramic reinforcement phases of TiC,Cr7C3 and Cr5B3 were randomly distributed in the binder phases of Ni31Si12 and(Ni,Fe)solid solution;The coating had about 15vol%pores and can possibly be applied as a self-lubrication coating;The coating and the substrate were integrated together by metallurgical bonding;The coating had a hardness up to 91-94HR15N.

Wear resistance of Zr/WC composite coatings on Cr12MoV steel surface by electric spark deposition

Zr/WC composite coating was prepared on the surface of Cr12MoV steel by electric spark deposition technology to change its surface properties. The surface and worn surface morphology of the coating were observed using scanning electron microscope. Dry friction and wear tests of the coatings were carried out at room temperature. The results show that the coating is continuous and uniform, and the thickness was about 50-60 μm. The microhardness of the coating surface was highest at 1140 HV_(200g), which was significantly higher than that of the substrate. The ear tests results show that the wear weight loss, wear volume and wear rate follow the following rules: Cr12MoV>WC coating> Zr/WC composite coating.

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.

Oxidation behavior of Fe40Al-xWC composite coatings obtained by high-velocity oxygen fuel thermal spray

The Fe40Al-xWC(x=0,10,12,15)coatings with dense structure were successfully deposited by high-velocity oxygen fuel (HVOF)spraying of a mixture of Fe,Al and WC powders.The objective of the present work is to provide insight into the oxidation behavior of the as-deposited coatings at 650℃under 0.1 MPa flowing pure O2.The present results show differences in the oxidation behavior of Fe40Al coating and Fe40Al-xWC composite coatings.The irregular Fe2O3 layer is seen on the top surface of the composite coatings.Fe40Al coating and Fe40Al-15WC composite coating both suffer a catastrophic corrosion due to the formation of a porous structure during 24 h of oxidation.However,Fe40Al-10WC and Fe40Al-12WC composite coatings show a good oxidation resistance behavior due to their dense structure.

Influence of Interfacial Diffusion on Mechanical Property of Vacuum Fusion Sinter (VFS) WC-Co Composite Coating

The WC-Co composite coatings bonded tightly to steel substrate have been made by vacuum fusion sinter （VFS）. The concentration distribution of some components were measured by the electron probe, and the microstructure and morphology of VFS coatings were observed and analyzed by SEM, X-ray diffractometer and microhardness tester. Diffusion coefficient of every element was calculated by using the experimental results. The influence of the interracial diffusion on the microstructure, Vickers hardness and interracial bond strength of the VFS coatings was studied in detail. The experimental results show that there is a metallurgical bond area between the VFS WC-Co coatings and the steel substrate. The VFS coatings are characterized by the gradient hardness of the interface and the high bond strength to the steel substate, both of which are beneficial to the improvement of the wear resistance and corrosion resistance.

激光熔覆WC/316L复合涂层结构及磨损性能

为改善激光熔覆过程中WC增强金属基复合涂层分解与分布不均匀的问题,采用激光熔覆技术制备了50%WC含量的WC/316L复合涂层,分别采用扫描电子显微镜(SEM)、显微维氏硬度计、摩擦磨损试验机表征了熔敷层的组织形貌、硬度与摩擦磨损性能。结果显示,低热输入量可以防止WC颗粒下沉,提升熔覆层厚度方向上的WC颗粒分布均匀性;但WC的平面分布均匀性较差,同时低热输入导致WC颗粒结合较弱,易发生脱落;熔覆过程中,粉末中15%的WC发生分解。研究表明,通过降低激光热输入量,可以制备WC厚度方向较为均匀的复合涂层,提升熔覆层耐磨性,但是需要优化WC平面分布均匀性与WC颗粒结合性能。

激光能量密度对65Mn钢表面Ni60A/WC复合涂层摩擦磨损性能的影响规律

目的改善旋耕刀65Mn钢的摩擦磨损性能,提高农机触土零部件的使用寿命。方法采用激光熔覆技术在65Mn钢基体表面制备Ni60A/WC复合涂层。通过改变激光功率调节激光能量密度,在不同能量密度下制备Ni60A/WC复合涂层,观察并测试不同参数下复合涂层试样的宏观形貌、微观结构、物相组成、元素分布、显微硬度及摩擦磨损特性,研究激光能量密度对Ni60A/WC复合涂层组织演变及摩擦磨损性能的影响规律和机理。结果Ni60A/WC复合熔覆层顶部主要有胞状晶和树枝晶,分布较紧密,熔覆层中部主要有树枝状晶,熔覆层底部主要为胞状晶和垂直交界面生长的枝晶,且分布均匀致密。随着激光能量密度的升高,熔覆层的熔高和熔深增加显著,WC硬质相颗粒发生分解,硬质相的数量明显减少,涂层的平均显微硬度降低。在激光能量密度为120 J/mm^(2)时,熔覆层的平均显微硬度为587.1HV1.0,相较于基体,提升了约1.8倍。此时熔覆层的平均摩擦因数最小,为0.312,相较于基体,得到显著提升,摩擦磨损机制为轻微的磨粒磨损。经田间试验测试发现,在激光能量密度为120 J/mm^(2)时制备的带有熔覆层的旋耕刀相较于无熔覆层的旋耕刀,其磨损质量降低了63%。结论通过控制激光能量密度,可以有效调控Ni60A/WC熔覆层的硬度和耐磨性,可为农机触土易磨损件的减摩耐磨表面强化改性提供理论指导。

冷喷涂Ti/WC复合涂层的组织与耐磨性研究

为解决钛及其合金磨损性能较差的问题,采用高压冷喷涂技术在Ti6Al4V合金基体上沉积了2种不同成分的Ti/WC复合涂层,通过室温下的干滑动摩擦磨损试验分别测试了基体与复合涂层的摩擦性能,并采用扫描电镜及拉曼光谱对磨损表面进行了观察与表征。结果表明,与Ti6Al4V基体的磨损率(4.06×10-7 mm3/(N·m))相比,复合涂层的磨损率降低了一个数量级,表现出优异的耐磨性。此外,涂层内WC含量的增加,提高了涂层的显微硬度,涂层的耐磨性也随之提升。在磨损轨迹表面,由TiO2、WO3以及WC碎片构成的摩擦膜能够有效避免磨球与涂层表面的直接接触,从而降低磨损程度。因此,冷喷涂Ti/WC复合涂层在钛合金磨损防护方面具有一定的应用前景。

表面机械研磨法制备Ni+WC复合涂层的耐磨性研究

为强化TA1钛合金的组织结构并提高其耐磨损性能,采用行星式机械球磨装置,在Ni与WC 2种粉末配比分别为1∶1、2∶1、3∶1、4∶1及5∶1的5种混合型增强介质下对TA1合金进行表面机械复合强化处理,在0.05 MPa氮气气氛下,设定转速为350 r/min,时间为8 h,对TA1钛合金进行表面机械变形+固相涂层复合强化处理,这种一步法表面复合强化技术具有工艺简单、能耗少、涂层选材灵活等优势。结果显示:TA1钛合金表面形成由Ni+WC涂层+形变细晶区组成的复合强化层,涂层区厚度在40μm以上,其中Ni∶WC为3∶1时所得复合涂层内部缺陷最少,且连续均匀。在5 N、10 N载荷下Ni∶WC为3∶1摩擦系数相较于其他比例低,摩擦区间更加稳定且持续时间更长。2种载荷下磨损量均较TA1原样少,其中Ni∶WC为3∶1的强化样磨痕深度、磨损量均优异于其他4种配比,因此减摩效果最为优异。此种Ni、WC混合增强介质下表层机械复合强化工艺可大幅提升TA1钛合金表层耐磨损性。混合增强颗粒涂层具有较强的减摩效果,其磨损机制主要是磨粒磨损与氧化磨损。

Microstructure and bonding strength of Ni-based alloy coating

A Ni-Cr-B-Si coating technique was developed and successfully applied on austenite grey iron substrate in a conventional resistance furnace under graphite powder protection. The microstructure, phase distribution, chemical composition profile and microhardness along the coating layer depth were investigated. Shear strength of the coating was also tested. Microanalysis shows that the coating is consist of γ-Ni solution and γ-Ni+Ni3B lamellar eutectic, as well as small amount of Cr5B3 particles. Diffusion induced metallurgical bonding occurs at the coating/substrate interfaces, and the higher the temperature, the more sufficient elements diffused, the broader interfusion region and the larger bonding strength, but it has an optimum value. And the bonding strength at the interface can be enable to reach 250-270 MPa, which is nearly the same as that of processed by flame spray. The microhardness along the coating layer depth shows a gradient distribution manner.

激光熔覆复合涂层WC对裂纹产生机理影响研究

为了研究复合涂层中碳化钨(WC)组织演变对裂纹产生的影响机理,采用单层激光熔覆、过渡层梯度熔覆与双层熔覆制备3种Ni50A/WC复合涂层对比的方法,分析涂层的形貌与组织、裂纹产生特点以及原因,探究WC的组织演变对裂纹产生的影响。结果表明,不同熔覆方法的WC组织演变对裂纹产生的影响主要由残余WC颗粒内部开裂形成裂纹源、硬质相元素引起成分偏析等作用组成;双层熔覆、梯度熔覆涂层与单层熔覆涂层相比,由于粉末吸收了更多的能量,残余WC颗粒含量降低了32.7%与37.9%,减少了涂层内部裂纹源;共晶化合物的W元素质量分数也从单层熔覆涂层的0.534分别下降到双层熔覆涂层的0.417与梯度熔覆涂层的0.386,降低了硬质相元素集中程度,减少了涂层成分偏析,降低了涂层开裂敏感性。该研究对改善激光熔覆复合涂层的开裂问题、提高复合涂层的成品率有一定的指导意义。

电磁辅助激光熔覆IN718/WC复合涂层组织及性能

采用电磁复合场辅助激光熔覆制备IN718/WC复合涂层,系统地研究了涂层的宏观结构、微观组织、显微硬度和耐磨性能.结果表明,电磁复合场形成向下的安培力,增强了熔池中的Marangoni对流.增强的Marangoni对流使WC颗粒均匀分布在复合涂层中.然而,过度的Marangoni对流会导致WC颗粒从熔池中逸出,尤其是小的WC颗粒.20 mT稳态磁场与100 A直流电组合效果较好.WC颗粒在熔池中分解,形成亚微米共晶碳化物、羽毛状共晶碳化物和等轴共晶碳化物.其分解程度与WC颗粒的空间位置和颗粒之间的距离有关.颗粒的空间位置越高(相对于熔池),颗粒间的距离越大,分解越严重.此外,直流电提高了共晶碳化物的形核率,增强的马兰戈尼对流打断了长柱状共晶碳化物,这些作用共同细化了涂层的微观结构.在该复合场(20 mT,100 A)作用下,硬质相的衍射强度最高,涂层平均显微硬度为530 HV0.2,大于无能场下制备的涂层(400 HV0.2),缓解了涂层摩擦磨损过程中的黏着磨损形式.

WC含量对WC/Ni60涂层组织和性能的影响

在零件表面制备硬质涂层,可以在保持零件基体本身性能的基础上,改善零件的表面性能。利用表面粘涂技术和电接触强化技术在45钢基体表面制备WC/Ni60涂层,并通过扫描电子显微镜、硬度测试仪、摩擦磨损试验与热震试验研究了不同WC含量的涂层的组织与性能。结果表明,用表面粘涂技术先制备预涂层,然后用电接触强化技术对预涂层进行强化处理,可以在45钢基体表面制备出完整均匀的WC/Ni60涂层。在相同试验条件下,随着WC含量的增加,涂层硬度与抗热震性能提高;当WC含量为60%时,表面硬度最高,抗热震性能最好。当WC含量为50%时,磨损重最低,耐磨性最好。

不同含量WC颗粒增强激光熔覆截齿涂层性能研究

目的解决截齿磨损失效问题,研究不同WC颗粒含量对42CrMo截齿激光熔覆Co基/WC复合涂层表面形貌及裂纹率、显微硬度、耐磨/耐腐蚀性能的影响机制。方法通过在42CrMo截齿基体上制备Co基/WC复合涂层,利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、能谱仪(EDS)、显微硬度计、摩擦磨损试验仪及电化学工作站测试不同WC颗粒含量对熔覆层性能的影响。结果Co基/WC复合涂层表面较为平整,当WC颗粒质量分数大于30%时,熔覆层表面开始出现交错裂纹;当WC质量分数为80%时,裂纹率增加35%。Co基/WC复合涂层的显微硬度皆高于42CrMo基体(378HV0.2),随着WC颗粒含量的增加,熔覆层平均显微硬度从448HV0.2提升到890HV0.2。Co基/WC复合涂层的摩擦系数、磨损量均小于42CrMo基体,WC颗粒质量分数增加到80%时,熔覆层平均摩擦系数为0.270,为基体(0.567)的50%,磨损量仅为1.0 mg,相比于42CrMo基体(18.6 mg)降低了约95%,低WC颗粒含量以黏着磨损为主,高WC含量以磨粒磨损为主。熔覆层耐腐蚀性能随WC含量的增加先增大、后减小,WC质量分数为30%时,熔覆层的耐腐蚀性能最好,具有最小的电流密度(1.465×10^(–7)A/cm^(2)),相比基体电流密度(8.031×10^(–6)A/cm^(2))降低了98%。结论WC颗粒含量对Co基/WC复合熔覆层的裂纹敏感性有显著影响,WC颗粒的细晶、弥散及固溶强化使熔覆层的显微硬度、耐磨/耐腐蚀性能得到明显改善。

Nb对等离子熔覆NbC-WC/镍基复合涂层的组织性能的影响

采用等离子熔覆技术成功制备了不同(Nb+C)/WC比例的镍基复合涂层,借助高分辨扫描电镜、X射线衍射仪、显微硬度计、室温干滑动摩擦磨损试验机、三维形貌仪对复合涂层的组织及力学性能进行了表征。实验结果表明,涂层底部区域存在未熔WC颗粒,随着Nb含量的增加,WC的溶解行为得到促进;涂层由NbC、WC、γ(Fe,Ni)和M_(23)C_(6)组成;当n(Nb+C)∶n(WC)=2∶2时,涂层拥有较高的显微硬度(~750 HV_(0.1))、较好的耐磨性能和相对光滑平整的磨损形貌;随着Nb的添加,涂层的磨损机制由粘着磨损转变为粘着磨损和磨粒磨损。

Efect of Nanometer WC Coating on Thermal Conductivity of Diamond/6061 Composites

Diamond has poor interface tolerance with Al.To enhance interface bonding,in this study,tungsten carbide(WC)nanocoatings on the surface of diamond particles were prepared using sol–gel and in-situ reaction methods.WO_(3) sol–gel with two concentrations,0.2 mol/L,and 0.5 mol/L,was,respectively,coated on diamond particles,then sintered at 1250℃for 2 h to produce WC nanocoatings.The concentration of 0.2 mol/L WO_(3) sol–gel was not enough to cover the surface of the diamond completely,while 0.5 mol/L WO_(3) sol–gel could fully cover it.Moreover,WO_(3) was preferentially deposited on{100}planes of the diamond.WO_(3) converted to WC in-situ nanocoatings after sintering due to the in-situ reaction of WO_(3) and diamond.The diamond-reinforced Al composites with and without WC coating were fabricated by powder metallurgy.The diamond/Al composite without coating has a thermal conductivity of 584.7 W/mK,while the composite with a coating formed by 0.2 mol/L and 0.5 mol/L WO_(3) sol–gel showed thermal conductivities of 626.1 W/mK and 584.2 W/mK,respectively.The moderate thickness of nanocoatings formed by 0.2 mol/L WO_(3) sol–gel could enhance interface bonding,therefore improving thermal conductivity.The nanocoating produced by 0.5 mol/L WO_(3) sol–gel cracked during the fabrication of the composite,leading to Al12W formation and a decrease in thermal conductivity.

WC-10Co-4Cr含量对HVOF制备WC-10Co-4Cr/Ni60涂层性能的影响

为改善农业机械工作部件的耐磨性和耐腐蚀性能,提高其使用寿命,采用超音速火焰喷涂的技术,在45#钢表面制备WC-10Co-4Cr/Ni60涂层。在Ni60粉末中分别添加质量分数为0、10%、20%和30%的WC-10Co-4Cr粉末,探究WC-10Co-4Cr含量对WC-10Co-4Cr/Ni60涂层性能的影响。结果表明,制备的WC-10Co-4Cr/Ni60涂层组织均匀致密,涂层主要由γ(NiCr)相和WC相组成,含有少量的W_(2)C、Ni_(3)Fe和Cr_(3)Si相,没有明显的氧化脱碳现象。30%WC-10Co-4Cr/Ni60涂层的硬度达到9.35 GPa,是Ni60涂层的1.23倍,该涂层的耐磨性能最好,在摩擦115 m后,单位面积的总磨损量47.2 mg/cm^(2),比Ni60涂层减少了35.3%。20%WC-10Co-4Cr/Ni60涂层的断裂韧性最高为6.04 MPa·m^(1/2),相较于Ni60涂层提高了24.3%,此外,该涂层在酸性环境中的耐腐蚀性能均最佳。

WC-10Co4Cr含量对Ni基涂层磨损和腐蚀性能的影响

通过超音速火焰喷涂(AC-HVAF)在稀土镁合金表面制备WC-10Co-4Cr与Ni粉质量比为0∶10、1.5∶8.5、3∶7、4.5∶5.5的WC-Co-Cr-Ni涂层。分析了涂层的组织结构,研究了摩擦载荷、磨损速率对磨损性能的影响及涂层在盐溶液中的抗腐蚀性能。结果表明:4种涂层的组织均匀致密,当加入WC时形成了明显的层状结构。WC的质量分数为15%时涂层内部的缺陷稍有增加。WC含量增加时,涂层内部的缺陷减少,层状结构更明显。WC的质量分数为45%时,耐磨性最佳。WC的质量分数为15%的涂层磨损量较大。涂层在3.5%(质量分数)NaCl溶液中的微量缺陷影响其耐蚀性。WC质量分数为45%的涂层在腐蚀过程中表面易形成氧化物钝化膜,可提高涂层耐蚀性。

激光熔覆Stellite6–60WC复合涂层工艺及高温耐磨性

以Co基Stellite6合金与陶瓷(WC)为熔覆粉末,采用激光熔覆技术在沉没辊316L基体添加质量分数为60%的WC粉末,制备Stellite6-60WC熔覆层,分析激光功率、扫描速度、送粉量等工艺因素对熔覆层形貌的影响,确定最优熔覆工艺参数;且对复合涂层的物相、硬度和耐磨性进行研究,探讨熔覆层高温耐磨性能改善的机理。结果表明:激光功率1.5 kW、扫描速度300 mm/min、送粉速率18.8 g/min时,熔覆层表面质量较好,涂层与基体形成良好的冶金结合,表面无裂纹和孔洞;熔覆层的相组成主要为γ-Co,M_(7)C_(3),M_(23)C_(6)(M=Co,Cr,Fe),W_(2)C等硬质相,利于提高熔覆层的硬度,硬度可达736.2 HV,是基体的3.5倍;熔覆层的高温耐磨性优于316L基体,比基体提高了6.1倍,主要是熔覆层多种硬质强化相及未熔的WC颗粒所致。

高频感应熔覆WC增强Ni60合金涂层性能研究

采用高频感应熔覆方法在Q235低碳钢基体上制备了不同含量的WC增强Ni60A合金复合涂层。利用SEM和XRD分析了涂层的显微组织和相结构，并进行了耐磨性试验。结果表明，复合涂层中主要由WC、W2C、Cr7C3、Cr23C6、Cr2B、Ni2B、Ni3Si及Ni3Fe等相组成，并与基体实现了冶金结合。在相同试验条件下，涂层的硬度和耐磨性随WC含量的增加而提高，加入WC涂层的相对耐磨性为Ni60A涂层的2～6倍，当WC加入量为50％时涂层的耐磨性最好，为Ni60A涂层的6．5倍。涂层的磨损机制主要为轻微的塑性切削和硬质相的脆性剥落。