HVOF喷涂Cr3C2-NiCr涂层的磨粒磨损性能

探讨了氧气流量、燃气流量和喷涂距离三个喷涂工艺参数对ＨＶＯＦ喷涂Ｃｒ３Ｃ２－ＮｉＣｒ涂层硬度和磨粒磨损性能的影响。结果表明,燃气流量、氧气流量和喷涂距离对涂层的显微硬度和磨粒磨损性能的规律有所不同。在较高的燃气流量、适中的氧气流量和喷涂距离条件下,涂层具有较高的显微硬度;而氧气流量和燃气流量对涂层的磨粒磨损性能影响较大,适中的燃气流量条件下,涂层的磨粒磨损失重量较低,高的氧气流量条件下,磨损失重量     

超音速火焰喷涂钴基陶瓷涂层的组织与性能研究

本文在氧气流量和喷涂距离一定的条件下,研究了燃气流量对超音速火焰喷涂WC-Co涂层显微组织、相结构及性能的影响。结果表明:燃气流量低的涂层结合强度、显微硬度最低,孔隙率最大;燃气流量适中的涂层结合强度最高,显微硬度低于另外两种涂层,燃气流量最高的涂层,燃气流量高的涂层的显微硬度最大。     

中性盐雾对等离子喷涂NiCr-Cr3C2涂层摩擦磨损性能的影响

利用超音速等离子喷涂(SPS)技术制备了陶瓷相增强的NiCr-Cr3C2涂层,采用线接触往复滑动方式进行摩擦磨损实验,测定了NiCr-Cr3C2涂层/Q235碳钢摩擦副在盐雾腐蚀前后涂层的摩擦系数和磨损量,此外,还采用SEM、EDS等技术观察分析了涂层表面的形貌和微区元素分布,探讨了盐雾腐蚀环境对涂层摩擦磨损性能的影响。结果表明：NiCr-Cr3C2涂层的磨损机制主要为磨粒磨损,而盐雾腐蚀后的磨损机制为腐蚀磨损。盐雾腐蚀后涂层的摩擦系数比盐雾腐蚀前的摩擦系数降低了1/5;不过,盐雾腐蚀后涂层的磨损失重量是盐雾腐蚀前磨损失重量的5倍左右,说明盐雾腐蚀环境加速了其摩擦学性能的恶化,涂层的耐蚀性有待进一步提高。     

大气等离子喷涂和超音速火焰喷涂WC-Ni涂层组织结构和性能的对比研究

采用大气等离子喷涂和超音速火焰喷涂技术在不同工艺参数下制备WC-Ni涂层。涂层的相结构和显微组织结构分别采用X射线衍射(XRD)和扫描电镜(SEM)进行表征。涂层的显微硬度、弹性模量和断裂韧性采用显微维氏硬度计进行表征。采用销盘磨损试验对涂层的磨损性能进行表征。结果表明,较大功率下等离子喷涂的涂层较致密,WC相脱碳程度较大。超音速火焰喷涂距离较小时,制备的涂层较致密,脱碳分解程度较小。相比等离子喷涂技术,超音速火焰喷涂制备的涂层中WC相的分解更少,涂层组织结构相对致密,力学性能相对较高,耐磨粒磨损性能较好。致密度相近,但脱碳程度较小的涂层耐磨性能较好。     

超音速火焰喷涂耐磨性TiC-Ni金属陶瓷涂层

石油大学(华东)机电工程学院材料科学与工程系利用超音速火焰喷涂合成技术制备了3种不同Ni含量的TiC—Ni金属陶瓷涂层，并对涂层进行了组织和性能研究。结果表明，Ni在喷涂过程中起到了吸收反应热，减缓喷涂合成过程中粉末组分的氧化，并且在涂层中起到作粘结相金属的作用。原料中的Ni含量对涂层的组织和性能影响很大。Ni含量较低时涂层巾含有大量氧化物，涂层组织疏松。涂层的耐滑动磨损性能较差；随着Ni含量的升高，涂层的氧化物含量降低，耐滑动磨损性能增强；     

中性盐雾腐蚀对等离子喷涂NiCr-Cr_3C_2涂层摩擦磨损性能的影响

利用超音速等离子喷涂(SPS)技术制备了陶瓷相增强的NiCr-Cr_3C_2涂层,采用线接触往复滑动方式进行摩擦磨损实验,测定了NiCr-Cr_3C_2涂层/Q235碳钢摩擦副在盐雾腐蚀前后涂层的摩擦系数和磨损量,此外,还采用SEM、EDS等技术观察分析了涂层表面的形貌和微区元素分布,探讨了盐雾腐蚀环境对涂层摩擦磨损性能的影响。结果表明:NiCr-Cr_3C_2涂层的磨损机制主要为磨粒磨损和氧化磨损,而盐雾腐蚀后的磨损机制为粘着磨损、磨粒磨损和腐蚀磨损。盐雾腐蚀后涂层的摩擦系数比盐雾腐蚀前的摩擦系数降低了1/5;不过,盐雾腐蚀后涂层的磨损失重量是盐雾腐蚀前磨损失重量的5倍左右,说明盐雾腐蚀环境加速了其摩擦学性能的恶化,涂层的耐蚀性有待进一步提高。     

多尺度WC-17Co热喷涂层的组织结构与耐磨损性能

采用超音速火焰喷涂技术在4种氧气流量条件下制备多尺度WC-17Co金属陶瓷涂层,研究不同氧气流量对涂层的组织结构与耐磨损性能的影响。通过扫描电子显微镜和X射线衍射仪分别对涂层的微观组织形貌和物相进行分析,对4种涂层的硬度和耐磨损性能进行了测试。研究结果表明:所制备的4种涂层组织致密,孔隙率低,涂层与基体结合良好;随着氧气流量降低,涂层中WC陶瓷相分解逐渐增加;涂层的硬度值分布在862±10.5 HV0.3(322 L/min)至938.4±19.9 HV0.3(543 L/min)之间,涂层硬度值随氧气流量增大而增加;经过磨损试验发现,涂层磨损量随氧气流量增加而降低,涂层磨损量分布在8.58±0.04 mg(543 L/min)至15.82±0.17 mg(322 L/min)。     

热喷涂工艺对涂层摩擦磨损性能的影响

采用超音速火焰喷涂和爆炸喷涂法在金属表面制备了WC-Co单层涂层和NiCrAl／WC-Co梯度涂层，对涂层的室温干摩擦磨损性能进行了测定和分析。结果表明，超音速火焰喷涂WC-Co单层涂层具有最好的综合磨损性能。梯度涂层较好的结合力对摩擦磨损性能的影响只有在轻载时表现明显。涂层中原有的孔隙和摩擦过程中形成的孔洞可以在一定程度上减轻磨损，而不同条件下形成的磨屑对涂层的摩擦性能亦有较大影响。     

燃气流量对超音速火焰喷涂Cr3C2-NiCr涂层组织与冲蚀性能的影响

在氧气流量和喷涂距离一定的条件下,揭示了燃气流量对超音速火焰喷涂Cr3C2-NiCr涂层显微结构及冲蚀性能的影响,并探讨了冲蚀角度对Cr3C2-NiCr涂层冲蚀性能的影响.结果表明: 在相同冲蚀角度下,高燃气流量制备的涂层损耗率小;随着冲蚀角度的增加,涂层的损耗率逐渐增加;在90°时,损耗率达到最大.     

CoCrMoSi涂层冷热疲劳和磨损性能

采用超音速火焰喷涂技术,在CrZrCu表面制作了CoCrMoSi涂层.采用光学显微镜、SEM及EDS等方法,对涂层的冷热疲劳性能和抗磨损性能进行了分析研究,并与当前冶金行业大量使用的电镀NiCo镀层进行对比.结果表明,450 ℃试验条件下,经113次冷热疲劳后,CoCrMoSi合金涂层仍完好无损,而NiCo电镀层循环37.8次就剥落30%以上;CoCrMoSi涂层和NiCo镀层均发生了磨粒磨损和粘着磨损,镀层以粘着磨损为主,同时伴有严重的磨粒磨损,而涂层磨粒磨损不明显,主要表现为粘着磨损.涂层的抗磨损性能远高于电镀层,同样磨削条件下(30 min),电镀层失重0.598 6 g时,喷涂层仅仅失重0.057 2 g,电镀失重是喷涂的10.5倍还多.     

超音速火焰喷涂Cr3C2-NiCr涂层磨粒磨损行为

采用橡胶轮磨损实验机，对不同工艺条件下三种类型粉末制备的HOVF Cr3C2-25％NiCr涂层进行了磨粒磨损实验，发现该涂层的磨损失重量与磨程基本呈现线性关系，磨损率远低于低碳钢。氧气流量，燃气流量适中的条件下制备的涂层磨损率较低，用团聚致密化工艺制备的粉末沉积的涂层耐磨粒磨损性能较好，涂层的磨损机制主要为先期的粘结相优先切削和随后的碳化物剥落，其中碳化物的剥落对磨损过程起制约作用。     

Effect of flame conditions on abrasive wear performance of HVOF sprayed nanostructured WC-12Co coatings

Nanostructured WC-12Co coatings were deposited by high velocity oxy-fuel (HVOF) spraying with an agglomerated powder. The effect of flame conditions on the microstructure of the nanostructured coatings was investigated. The wear properties of the coatings were characterized using a dry rubber-wheel wear test. The results show that the nanostructured WC-Co coatings consist of WC, W2C, W and an amorphous binder phase. The microstructure of the coating is significantly influenced by the ratio of oxygen flow to fuel flow. Under the lower ratio of oxygen/fuel flow, the nanostructured coating presents a relative dense microstructure and severe decarburization of WC phase occurs during spraying. With increasing ratio of oxygen/fuel flow, the bonding of WC particles in the coating becomes loose resulting from the original structure of feedstock and the decarburization of WC becomes less owing to limited heating to the powder. Both the decarburization of WC particles in spraying and the bonding among WC particles in the coatings affect the wear performance. The examination of the worn surfaces of the nanostructured coatings reveals that the dominant wear mechanisms would be spalling from the interface of WCCo splats when spray particles undergo a limited melting. While the melting state of the spray particles is improved,the dominant wear mechanisms become the plastic deformation and plowing of the matrix and spalling of WC particles from the matrix.     

Tribological properties of TiC-Fe coatings obtained by plasma spraying reactive powders

Titanium carbide-based coatings have been considered for use in sliding wear resistance applications. Carbides embedded in a metal matrix would improve wear properties, providing a noncontinuous ceramic surface. TiC-Fe coatings obtained by plasma spraying of spray-dried TiC-Fe composite powders containing large and angular TiC particles are not expected to be as resistant as those containing TiC particles formed upon spraying. Coatings containing 60 vol% TiC dispersed in a steel matrix deposited by plasma spraying reactive micropellets, sintered reactive micropellets, and spray-dried TiC-Fe composite powders are compared. The sliding wear resistance of these coatings against steel was measured following the test procedure recommended by the Versailles Advanced Materials and Standards (VAMAS) program, and the inherent surface porosity was evaluated by image analysis. Results show that, after a 1-km sliding distance, TiC-Fe coatings obtained after spraying sintered reactive powders exhibit scar ring three times less deep than sprayed coatings using spray-dried TiC-Fe composite powders. For all coatings considered, porosity is detrimental to wear performance, because it generally lowers the coating strength and provides cavities that favor the adhesion of metal. However, porosity can have a beneficial effect by entrapping debris, thus reducing friction. The good wear behavior of TiC-Fe coatings manufactured by plasma spraying of sintered reactive powders is related to their low coefficient of friction against steel. This is due to the microstructure of these coatings, which consists of 0.3 to 1 μm TiC rounded particles embedded in a steel matrix. Presented at the International Conference on Metallurgical Coatings and Thin Films, ICMCTF-92, Apr 6–10, 1992, San Diego.     

Study of plasma- and detonation gun-sprayed alumina coatings using taguchi experimental design

Atmospheric plasma spraying (APS) is a most versatile thermal spray method for depositing alumina (Al₂O₃) coatings, and detonation gun (D-gun) spraying is an alternative thermal spray technology for depositing such coatings with extremely good wear characteristics. The present study is aimed at comparing the characteristics of Al₂O₃ coatings deposited using the above techniques by using Taguchi experimental design. Alumina coating experiments were conducted using a Taguchi fractional-factorial (L₈) design parametric study to optimize the spray process parameters for both APS and D-gun. The Taguchi design evaluated the effect of four APS and D-gun spray variables on the measured coating attributes. The coating qualities evaluated were surface roughness, porosity, microhardness, abrasion, and sliding wear. The results show that the coating quality is directly related to the corresponding coating microstructure, which is significantly influenced by the spray parameters employed. Though it is evident that the D-gun-sprayed coatings consistently exhibit dense and uniform microstructure, higher hardness, and superior tribological performance, the attainment of suitable plasma-sprayed coatings can be improved by employing the Taguchi analysis.     

Sliding and abrasive wear resistance of thermal-sprayed WC-CO coatings

We studied the resistance of the coatings to abrasive and unlubricated sliding wear of 40 WC/Co coatings applied by high velocity oxygen fuel (HVOF), high-energy plasma spray (HEPS), and high velocity plasma spray (HVPS), using commercial and nanostructured experimental powders. The hardness of the coatings varies from 3 to 13 GPA, which is much lower than that of sintered samples (10 to 23 GPA) because of the porosity of the coatings. Phase analysis by x-ray diffraction revealed various amounts of decarburization in the coatings, some of which contain WC, W₂C, W, and η phase. The abrasive and sliding wear resistance is limited by the hardness of the samples. For a given hardness, the wear resistance is lowered by decarburization, which produces a hard but brittle phase. Nanocarb powders have the shape of thin-walled hollow spheres that heat up rapidly in the gun and are more prone to decarburization than commercial materials. The work shows that, in order to obtain the performance of nanostructured coatings, the powder and spray techniques must be modified.     

不同参数下超音速火焰喷涂Cr_3C_2-NiCr涂层磨粒磨损性能

通过超音速火焰(HVOF)技术,采用不同的工艺参数在低碳钢表面喷涂Cr_3C_2-NiCr涂层;对所得涂层进行磨粒磨损实验.同时考察低碳钢磨损性能,比较喷涂层之间的磨损性能及其与基体的磨损性能.采用光学金相显微镜观察涂层断面的形貌,通过显微硬度计测试涂层的显微硬度.结果表明.Cr_3C_2-NiCr涂层磨损质量损失与磨程基本呈线性关系;涂层的磨损性能高于低碳钢;不同参数制备的涂层,其磨粒磨损性能也不一样,其中燃气流量为38 L/min时的涂层磨损性能较好,该条件下涂层的断面显微组织呈现层状结构,其显微硬度也较高.     

铝合金基体电热爆炸喷涂钼涂层的制备工艺与性能

采用电热爆炸喷涂技术在铝合金基体上制备钼涂层,用SEM、划痕仪、显微硬度计、表面粗糙度仪、微磨损试验机等表征了涂层性能。借助正交试验方法分析了钼涂层制备中各工艺参数对涂层质量的影响,确定了最佳工艺参数。结果表明:用电热爆炸喷涂方法制备的钼涂层均匀致密,孔隙率低;涂层与基体形成冶金结合,结合强度高;涂层硬度为基体的4.9倍,体积磨损量仅为基体的11.2%,耐磨性大幅增加。电爆炸喷涂的工艺参数中,对涂层质量和结合力影响最大的是喷涂距离,其次是喷涂次数,影响最小的是喷涂电压。     

Sliding wear evaluation of hot isostatically pressed thermal spray ceramet coatings

The principal aim of this study was to compare the sliding wear performance of as-sprayed and Hot Isostatically Pressed (HIPed) thermal spray cermet (WC-12Co) coatings. Results indicate that HIPing technique can be successfully applied to post-treat thermal spray cermet coatings for improved sliding wear performance, not only in terms of coating wear, but also in terms of the total volume loss for test couples. WC-12Co coatings sprayed by a HVOF system were deposited on SUJ-2 bearing steel substrate and then encapsulated and HIPed at 850 °C for one hour. A high frequency reciprocating ball on plate rig was used to measure the sliding wear resistance of these coatings in dry conditions under steel and ceramic contact configurations at two different loads. Results are discussed in terms of coating microstructure, microhardness, fracture toughness and residual stress evaluations. Microstructural investigations indicate fundamental changes in grain morphology, whereas x-ray diffraction revealed beneficial transformations in phase composition of these coatings during the HIPing post treatment. The effects of these microstructural changes on the physical properties and wear resistance are discussed.     

Propylene flow,microstructure and performance of WC–12Co coatings using a gas-fuel HVOF spray process

Five WC–12Co coatings were deposited by a high velocity oxy-fuel (HVOF) system using constant oxygen flow and varying propylene flow. The phase composition, microstructure, as well as abrasive and sliding wear performance of the as-sprayed coatings were investigated. The degree of tungsten carbide (WC) decarburization in the as-sprayed coatings increases while the coating porosity decreases with the increase of the propylene flow. The coating hardness, fracture toughness, resistance to abrasive and sliding wear increases with the increase of the propylene flow, reaches maximum and then decreases. At the low flow of the propylene, relatively loose coating microstructure is formed, which leads to fracturing and pulling off the WC particles during abrasive and sliding wear process. Herewith, at the high flow of the propylene, the high degree of the WC decarburization and high brittleness of the coating leads to micro-cutting during abrasive wear as well as to cracking and delamination of the coating in the sliding wear process.