不同喷涂方法制备WC－Co涂层性能的研究

介绍超音速火焰、等离子、氧乙炔火焰三种喷涂方法，在钢基体上喷涂钴包碳化钨粉末所制备涂层的工艺性能、结合强度、耐磨性能和机理。结果表明，三种喷涂方法都可制备ＷＣ－Ｃｏ金属陶瓷涂层；超音速火焰喷涂涂层的性能最好，其耐磨性能与硬质合金ＹＴ５相当；氧乙炔火焰喷涂涂层具有一定的耐磨性能。     

不同喷涂方法制备WC—Co涂层性能的研究

介绍超音速火焰、等离子，氧乙炔火焰三种喷涂方法，在钢基体上喷涂钴包碳化钨粉末所制备涂层的工艺性能，结合强度，耐磨性能和机理。结果表明，三种喷涂方法都可制备ＷＣ－Ｃｏ金属陶瓷涂层；超音速火焰喷涂涂层的性能最好，其耐磨性能与硬质合金ＹＴ５相当；氧乙炔火焰喷涂层具有一定的耐磨性能。     

超音速火焰喷涂WC-17Co合金涂层修复飞机燃油接受探管导轨磨损部位

某型飞机燃油接受探管外筒导轨镀铬层发生磨损剥落,采用超音速火焰(HVOF)喷涂WC-17Co合金涂层对其进行修复,研究了HVOF涂层的微观形貌、力学性能和耐磨性能,并对导轨修复的燃油接受探管进行了20次全行程收放转换模拟试验、30次地面运行试验和50次空中飞行运行试验。结果表明:HVOF涂层的硬度高达1 041 HV,与导轨基体的结合强度大于85.4MPa,涂层韧性良好,耐磨性能优于电镀铬层的,且与化学镀镍磨轮配对时的对磨表面磨损程度很小;修复导轨组装的探管在收放转换模拟试验和运行试验后,其HVOF涂层均未见磨损现象,修复导轨的使用状态良好。     

高速火焰喷涂工艺参数对镍基-碳化钨复合涂层结合强度的影响

利用高速速火喷涂技术在铜基体上制备了镍基一碳化钨复合涂层,采用正交试验法研究了喷涂工艺参数对镍基复合涂层结合强度的影响.结果表明:影响镍基复合涂层与铜基体结合强度的主要工艺参数是燃气压力,其次是喷涂距离和前处理时的喷砂压力;涂层具有良好结合强度的最佳工艺参数为喷涂距离170 mm,燃气压力0.49 MPa,喷砂压力0.4 MPa.     

颗粒致密度对WC-10Co-4Cr涂层性能的影响

利用超声速火焰喷涂技术(High velocity oxygen fuel,HVOF)并采用两种不同颗粒致密度的WC- 10Co-4Cr合金粉末在300M钢表面制备涂层.采用扫描电镜、X射线衍射仪、显微硬度计等设备对两种涂层的微观组织结构及特性进行分析,重点研究碳化钨颗粒的沉积过程,并通过腐蚀电化学试验研究两种涂层的耐...     

HVOF超音速火焰喷涂WC10Co4Cr涂层的研究

通过对HVOF超音速火焰喷涂WC10Co4Cr涂层的工艺研究,确定合理的喷涂工艺参数,并探讨喷涂工艺各因素对涂层的影响。涂层的金相组织、显微硬度、结合强度等性能测试结果表明:HVOF超音速火焰喷涂WC10Co4Cr涂层符合图纸的涂层性能要求。     

超级不锈钢涂层在风机主轴修复上的应用研究

为了解决风机主轴因磨损带来的尺寸超差问题,采用超音速火焰喷涂(HVOF)技术制备超级不锈钢涂层试样,并对试样的截面形貌、硬度、结合强度、耐磨性开展检测研究.结果表明,超级不锈钢涂层致密,孔隙率为1.26％,与基体的结合强度达到73.33Mpa,涂层具有与比基体1Cr13更高的硬度和更好的耐磨性能.由此,提出用HVOF技...     

煤化工用调节阀耐磨涂层工艺技术研究

针对煤化工用调节阀的特殊工况,为了提高阀内件表面的耐磨性,采用超音速火焰喷涂(high velocity oxy-fuel,HVOF)、等离子喷涂(atmospheric plasma spray,APS)及熔敷、等离子堆焊(plasma transferred arc,PTA)3种典型的处理工艺,并结合上述工艺选取与之相匹配典型的喷涂材料.通过磨损试验、硬度测试和显微组织结构的研究发现:APS喷涂的温度较高,引起碳化物分解并溶解于基体内,经过熔敷,涂层韧性增加,磨损表面不易产生裂纹和剥落;HVOF喷涂过程中,粒子的撞击速度高,不会产生过热现象,涂层受压应力、密度高,耐磨性好;PTA堆焊的涂层和基体的结合力较强,硬度高,涂层厚度大,耐磨性介于APS和HVOF之间.     

等离子喷涂技术在油膜轴承密封件上的应用

在介绍等离子喷涂技术和主要工艺参数的基础上,分析了油膜轴承密封件使用等离子喷涂的优势,并对比了油膜轴承密封件常用陶瓷涂层的喷涂参数与性能.     

ZrO2热障涂层耐高温冲刷性能研究

采用等离子喷涂工艺制备了NiCoCrAlY／ZrO2热障涂层，利用超音速火焰喷涂（HVOF）ZrO2粒子高速冲刷涂层表面，考察ZrO2热障涂层的耐高温冲刷性能。结果表明，等离子喷涂NiCoCrAlY／ZrO2热障涂层具有较好的耐高温冲刷性能，经高温高速粒子冲刷20s后，涂层与基体结合良好，涂层完整，未出现大面积的剥落。等离子喷涂ZrO2热障涂层高温冲刷的主要磨损机理为脉动冲击作用造成的裂纹扩展、涂层颗粒变形磨损和微切削。涂层的耐高温冲刷性能主要取决于涂层的硬度。     

Elevated temperature erosion–corrosion of thermal sprayed coatings in chlorine containing environments

A series of hot erosion and erosion–corrosion (E–C) tests was carried out on thermal sprayed coatings, diffusion coatings and boiler steels using a burner-rig type elevated temperature E–C tester in order to evaluate the possibility to utilise thermal sprayed coatings in shielding of boiler components. Test conditions simulated the E–C conditions in the superheater section of a circulating fluidised bed combustor (CFBC). Carbide containing HVOF coatings performed well in erosion tests, as expected. Also diffusion coatings and nickel-based, high-chromium HVOF coatings performed well. In E–C tests in presence of chlorine, nickel-based HVOF coatings performed the best, whereas carbide containing HVOF coatings and diffusion coatings wore away.     

The role of lubrication and corrosion in abrasion of materials in aqueous environments

A rubber wheel type test apparatus has been constructed which allows abrasion testing to be conducted in slurry or dry environments in otherwise identical conditions. Abrasion tests of a steel, a sintered tungsten carbide–cobalt hardmetal and an HVOF sprayed nickel chrome–chromium carbide cermet coating have been performed in dry and aqueous slurry conditions, the latter with both neutral and acidic carriers. It has been shown that the aqueous carrier acts as an effective lubricant and thus significantly reduces the abrasion rate over that observed in dry conditions. However, enhancement of corrosion by use of an acid slurry lead to an increase in the rate of material removal over that of the neutral aqueous conditions in all cases. Increases were small for the corrosion resistant cermet coating and moderate for the steel. Significant enhancement of wear was observed for the sintered WC–Co hardmetal where rapid removal of the cobalt binder by the acid resulted in a change in dominant mechanism of carbide removal from attritive wear to pullout.     

钴基合金-碳化钨复合涂层材料耐磨性能的研究

采用真空熔烧法制得钴基合金—碳化钨复合涂层材料,借助扫描电子显微镜、X射线衍射仪等先进的测试手段对涂层的组织结构和表面形貌进行观察分析。应用盘销式摩擦磨损试验机对不同碳化钨质量分数的复合涂层材料和淬火态45钢进行了磨损试验。结果表明:在相同试验条件下,复合涂层的耐磨性显著高于淬火钢,且其耐磨性随碳化钨质量分数的增加而提高:淬火钢的耐磨性随着载荷的增加迅速降低,而复合涂层的耐磨性则变化不大。     

Abrasion Resistance of Thermal Sprayed Composite Coatings with a Nickel Alloy Matrix and a WC Hard Phase. Effect of Deposition Technique and Re-melting

Coatings resulting from the spraying of mixtures with different proportions of two commercial alloys, a nickel self-fluxing alloy and a tungsten carbide with cobalt, have been produced using two flame-spraying techniques: HVOF, and powder oxy-acetylene flame spraying. The effect of both hard-phase content and coating-spraying technique on abrasion resistance is discussed in terms of the coatings' mechanical properties and microstructure.     

超音速火焰喷涂WC涂层超高速磨削试验研究

针对超音速火焰喷涂碳化钨涂层存在的加工困难,研究了不同砂轮线速度对涂层磨削力、表面粗糙度及表面微观形貌的影响,试验结果表明,随着砂轮线速度的大幅度提高,涂层磨削力、表面粗糙度值都能得到明显的减小;通过观察磨削表面的微观形貌发现,在超高速磨削条件下,涂层材料的去除方式更多的以塑性去除为主.     

Fine-particle slurry wear resistance of selected tungsten carbide thermal spray coatings

The surface degradation of tungsten carbide based thermal spray coatings when exposed to fine-particle slurry abrasion has been investigated. The coatings that were studied contain binder-phase constituents consisting of either nickel or cobalt. The coatings were deposited onto test cylinders using a detonation gun device. After applying approximately 0.15 mm thickness of thermal spray coating, the coatings were ground, then diamond polished to achieve surface roughnesses of 0.03 μm Ra or less. The coatings were exposed to a three-body abrasive wear test involving zirconia particles (less than 3 μm diameter) in a water-based slurry. Results show that preferential binder wear plays a significant role in the wear of these tungsten carbide coatings by fine abrasives. In the comparison presented here, the coating containing nickel-based binder with a dense packing of primary carbides was superior in terms of retaining its surface finish upon exposure to abrasion. The coating containing a cobalt binder showed severe surface degradation.     

A scanning electron microscope study of attrition wear in tungsten carbide taper pin reamers

The wear of tungsten carbide taper pin reamers used to ream holes in a composite structure of aluminium alloy plate overlaying a plate of ultra-high strength steel was examined under the scanning electron microscope. The predominant process of wear was by attrition, which involved the mechanical detachment of individual or groups of tungsten carbide grains from the reamers by both the swarf and workpiece material.This process of attrition wear was initiated by the removal of the cobalt binder phase, resulting in the undermining and subsequent removal of tungsten carbide grains. A mechanism is described for explaining how the cobalt binder phase is initially removed, and the means by which tungsten carbide grains are then removed are discussed. Consequent on the removal of tungsten carbide grains some cobalt binder phase attached to these grains is also removed, and this subsequently becomes an important mechanism of cobalt binder phase removal.     

Evaluation of surface residual stresses in HVOF sprayed WC-12Co coatings by XRD and ED-hole drilling

Thermally sprayed coatings are inherently associated with residual stresses in the coatings. These stresses have a noticeable effect on the physical and mechanical properties of coatings. The high speed hole drilling method is widely used to measure the residual stress. Due to the nature of the thermally sprayed coatings, the application of this method for WC/Co coatings has some limitations. In the current study, WC-12Co coatings were deposited using HVOF thermal spraying. The electro discharge hole drilling method was developed to measure the through thickness residual stress in WC-Co thermally sprayed coatings. Morphological studies were conducted using optical microscopy and scanning electron microscopy (SEM) to evaluate the powder and coating characteristics. The sin²ψ method was used to evaluate the surface residual stress by means of XRD. The residual stress at the surface using EDM and XRD was approximately ?32.54 MPa and ?40.6 MPa respectively. The experimental results reveal that the stress curves are not uniform through the coating thickness. It has been found that the mean residual stress is of approximately ?126 MPa. Obtained results are in good agreement with the reported values from literatures. The developed method confirms the feasibility of residual stresses measurement for HVOF thermally sprayed WC-Co coatings.     

A contribution to the surface analysis and characterisation of HVOF coatings for petrochemical application

The appropriate selection of bulk materials and coatings of valve components is an important factor for the economic success of oil and gas production activities in the petrochemical field. Materials and coatings are important because particle erosion and surface wear are associated to corrosion by hydrogen sulphide during oil and gas flow. The wear of high pressure valves of gas system will lead to pollution, safety problems and cost increases. The most common solution of these problems is the deposition of hard materials as tungsten carbide or chromium carbide by thermal spray. These coatings are deposited by high velocity oxygen fuel (HVOF) thermal spray process to obtain a very high hardness with excellent cohesion and adhesion. Tungsten carbide cobalt–chromium based coating, chromium carbide nickel–chromium coating as well as Inconel 625 have been adopted in the specifications of petrochemical companies and their behaviour and wear, erosion and corrosion properties are reported in the literature.

This paper addresses the experimental study, surface analysis and functional characterisation of HVOF coatings innovative for the specific application such as NiAl and composite material WC/intermetallic compounds containing Ni, Cr, Co and Mo. These coatings have been systematically submitted to corrosion and functional tests based on the determination of the behaviour of the coatings in H₂S and CO₂ atmosphere and to wear and erosion according to standard ASTM G75-95 (slurry test); material loss and surface damage have been determined; the coatings have been completely characterised from the point of view of the structure (morphology, porosity, hardness, wear) and of the surface properties by means of a prototype 3-dimensional (3-D) stylus micro-geometrical surface analysis system; their corrosion and functional behaviour have been compared with the behaviour of the above mentioned coatings.

The slurry test allows a clear discrimination among the performances of analysed coatings. Namely, WC/Mo compound, because of its carbide content, shows fairly good behaviour in an erosive environment and higher erosion resistance than Inconel 625 and NiAl; all the tested coatings show similar behaviour in a corrosive environment.     

Wear prevention in molds used to mold boron filled elastomers

An investigation was conducted to identify surface coatings which would improve the wear characteristics of compression molds used to mold contoured parts from elastomers filled with crystalline boron particles. An analysis was made of the mode of wear present on the surfaces of a production mold, followed by selection and modification of a capillary rheometer as the test device. Test specimens were coated by electroplating, electroless plating, plasma spraying, chemical vapor deposition, sputtering and a fused salt process. Testing was conducted under conditions simulating those encountered in the production molding operation.Techniques used in evaluating the results included optical microscopy, scanning electron microscopy, transmission electron microscopy and surface profilometry. The results are expressed as a ratio of volumetric wear of the tested coating to that of unprotected mold steel.Results indicate that titanium diboride (TiB₂) applied by chemical vapor deposition provides wear resistance superior to plasma sprayed aluminum oxide mixed with titanium dioxide, plasma sprayed chromium oxide, electrodeposited chromium, electroless nickel containing synthetic diamond powder, chemical vapor deposited tungsten carbide (W/W₂C), aluminum oxide and aluminum oxide over chromium carbide. Sputtered titanium diboride was also superior to these coatings and to sputtered titanium carbide and boron carbide.