超音速火焰喷涂Fe基非晶合金涂层材料的摩擦磨损性能研究

目的通过优化涂层制备工艺,制备致密的Fe基非晶合金涂层,以提高非晶合金涂层的耐磨性。方法采用活性燃烧高速燃气超音速火焰喷涂(AC-HVAF)技术,通过工艺优化,制备了组织致密的Fe基非晶合金涂层。利用场发射扫描电子显微镜、X射线衍射仪、维氏显微硬度计、摩擦磨损试验机、三维光学轮廓仪等设备,对非晶合金涂层的组织结构、摩擦性能和磨损机制进行了深入分析。结果 Fe基非晶合金涂层呈现典型的非晶结构,涂层厚度在300μm左右,涂层的平均显微硬度值高达1000HV0.1。在干摩擦试验条件下,Fe基非晶合金涂层的磨损量远低于304不锈钢材料,磨损率是304不锈钢基体的1/3~1/2。Fe基非晶合金涂层的磨损机制以疲劳磨损为主,伴随着氧化磨损。氧化磨损主要是由干摩擦过程中产生的摩擦热导致,氧化磨损加速了片层剥落。结论 Fe基非晶合金涂层孔隙率的降低和非晶相含量的提高,有利于稳定摩擦系数和改善涂层的耐磨损性能。     

Synthesis and characterization of Y3Al5O12 and ZrO2-Y2O3 thermal barrier coatings by combustion spray pyrolysis

Y₃Al₅O₁₂ and ZrO₂-Y₂O₃ (8 mol% YSZ) coatings for potential application as thermal barrier coatings were prepared by combustion spray pyrolysis. Thermal cycling of as deposited coatings on stainless steel and FeCrAlY bond coat substrates was carried out at 1000 °C and 1200 °C to determine the thermal fatigue response. Structural and morphological studies on Y₃Al₅O₁₂ and 8 mol% YSZ coatings before and after thermal cycling have been carried out. It has been noted that the coatings on FeCrAlY substrates remain intact after 50 cycles between room temperature and 1200 °C, whereas the coatings on stainless steel show some minor damage such as peeling off near the periphery after 50 cycles at 1000 °C. Thermal diffusivity values of Y₃Al₅O₁₂ and 8 mol% YSZ films were measured by using photo thermal deflection spectroscopy and the values are lower than those of coatings produced by conventional techniques such as EBPVD and APS.     

Characterization of plasma sprayed Fe-17Cr-38Mo-4C amorphous coatings crystallizing at extremely high temperature

A Fe-17Cr-38Mo-4C alloy powder was plasma sprayed by three processes: an 80 kW low-pressure plasma spray (LPPS), a 250 kW high-energy plasma spray (HPS), and a 40 kW conventional plasma spray (APS). The as-sprayed coating obtained by the LPPS process is composed of only amorphous phase. As-sprayed coatings obtained by the HPS and APS processes are a mixture of amorphous and crystalline phases. The three as-sprayed coatings exhibit a high hardness of 1000 to 1100 DPN. The amorphous phase in these coatings crystallizes at a high temperature of about 920 K. A very fine structure composed of hard ϰ-phase and carbides is formed after crystallization. The hardness of the coating obtained by LPPS reaches a maximum of 1450 DPN just after crystallization on tempering and retains a high hardness more than 1300 DPN after tempering at high temperatures of 1173 or 1273 K. The corrosion potential of the amorphous coating is the highest among the three coatings and higher than that of a SUS316L stainless steel coating. The anodic polarization measurements infer that the corrosion resistance of the amorphous coating is superior or comparable to SUS316L stainless steel coating in H₂SO₄ solution.     

FeCrNiMoCu高熵合金涂层的多靶磁控共溅射制备及微结构分析

采用多靶磁控共溅射技术的单靶功率可调特点,在304不锈钢基体上,制备出了FeCrNiMoCu高熵合金涂层。通过纳米压入(Nanoindentation)、X射线衍射仪(XRD)、扫描电子显微镜(SEM)、原子力显微镜(AFM)等对不同组分含量的FeCrNiMoCu高熵合金涂层的纳米硬度、微观结构及形貌进行了表征。结果表明:磁控共溅射法制备的FeCrNiMoCu涂层具有简单的fcc结构和高的纳米硬度,表面硬度随铁元素含量上升而增加。     

Effect of Plasma Nitriding and Nitrocarburizing on HVOF-Sprayed Stainless Steel Coatings

In this work, the effects of plasma nitriding (PN) and nitrocarburizing on HVOF-sprayed stainless steel nitride layers were investigated. 316 (austenitic), 17-4PH (precipitation hardening), and 410 (martensitic) stainless steels were plasma-nitrided and nitrocarburized using a N₂ + H₂ gas mixture and the gas mixture containing C₂H₂, respectively, at 550 °C. The results showed that the PN and nitrocarburizing produced a relatively thick nitrided layer consisting of a compound layer and an adjacent nitrogen diffusion layer depending on the crystal structures of the HVOF-sprayed stainless steel coatings. Also, the diffusion depth of nitrogen increased when a small amount of C₂H₂ (plasma nitrocarburizing process) was added. The PN and nitrocarburizing resulted in not only an increase of the surface hardness, but also improvement of the load bearing capacity of the HVOF-sprayed stainless steel coatings because of the formation of CrN, Fe₃N, and Fe₄N phases. Also, the plasma-nitrocarburized HVOF-sprayed 410 stainless steel had a superior surface microhardness and load bearing capacity due to the formation of Cr₂₃C₆ on the surface.     

304L stainless steel oxidation in carbon dioxide: An XPS study

From the early beginning of the oxidation of 304L stainless steel in carbon dioxide at 1273 K (1 min, for a weight gain of 0.02 mg cm⁻²), the surface of the alloy was entirely covered by oxides: magnetite Fe₃O₄, chromia Cr₂O₃ and traces of wüstite Fe_1−xO. Later on, for weight gains approaching 1 mg cm⁻², magnetite remained at the outer interface, with traces of hematite (Fe₂O₃), above a thick layer of wüstite Fe_1−xO. Magnetite and wüstite may favour adhesion of thermal plasma protective coatings such as alumina.     

Characterization of plasma sprayed Fe-10Cr-10Mo-(C,B) amorphous coatings

Alloys of Fe-10Cr-10Mo containing a large amount of carbon and/or boron were plasma sprayed by low-pressure plasma spraying (LPPS) and high-energy plasma spraying (HPS). The as-sprayed coatings obtained by the LPPS process are composed of only an amorphous phase, while as-sprayed coatings obtained by the HPS process are a mixture of amorphous and crystalline phases. The amorphous phase in these coatings crystallizes on tempering at about 773 to 873 K, and the crystallization temperatures depend on the content of carbon and boron. Thermal stability of the amorphous phase containing boron is higher than those phases containing carbon. A very fine mixed structure of ferrite and carbide, borocarbide, or boride is formed by decomposition of the amorphous phase, bringing about a hardness of 1200 to 1400 DPN (Vickers hardness). The coatings containing carbon retain a hardness of more than 1000 DPN, even on tempering at temperatures of 1073 K or higher. The anodic polarization behavior of the coatings exhibits an activation-passivation transition in 1N H₂SO₄ solution. The active and passive current densities of the as-sprayed amorphous and tempered crystalline coatings containing carbon is lower than the coatings containing boron. The corrosion resistance of the as-sprayed and crystallized coatings containing carbon is superior to a SUS316L stainless steel coating.     

Erosion and Corrosion Behavior of Laser Cladded Stainless Steels with Tungsten Carbide

Laser cladding of tungsten carbide (WC) on stainless steels 13Cr-4Ni and AISI 304 substrates has been performed using high power diode laser. The cladded stainless steels were characterized for microstructural changes, hardness, solid particle erosion resistance and corrosion behavior. Resistance of the clad to solid particle erosion was evaluated using alumina particles according to ASTM G76 and corrosion behavior was studied by employing the anodic polarization and open circuit potential measurement in 3.5% NaCl solution and tap water. The hardness of laser cladded AISI 304 and 13Cr-4Ni stainless steel was increased up to 815 and 725Hv_100?g, respectively. The erosion resistance of the modified surface was improved significantly such that the erosion rate of cladded AISI 304 (at 114?W/mm²) was observed ~0.74?mg/cm²/h as compared to ~1.16 and 0.97?mg/cm²/h for untreated AISI 304 and 13Cr-4Ni, respectively. Laser cladding of both the stainless steels, however, reduced the corrosion resistance in both NaCl and tap water.     

TiOxNy coatings grown by atmospheric pressure metal organic chemical vapor deposition

Titanium oxynitride coatings were deposited on various substrates by an original atmospheric pressure metal organic chemical vapor deposition (MOCVD) process using titanium tetra-iso-propoxide as titanium and oxygen precursors and hydrazine as a nitrogen source. The films composition was monitored by controlling the N₂H₄ mole fraction in the initial reactive gas phase. The variation of the N content in the films results in significant changes in morphological, structural and mechanical properties. When a large excess of the nitrogen source is used the resulting film contains ca 17  at % of nitrogen and forms dense and amorphous TiO_xN_y films. Growth rates of these amorphous TiO_1.5N_0.5 coatings as high as 14 μm/h were obtained under atmospheric pressure. The influence of the deposition conditions on the morphology, the structure, the composition and the growth rate of the films is presented. For the particular conditions leading to the growth of amorphous TiO_1.5N_0.5 coatings, first studies on the mechanical properties of samples grown on stainless steel have revealed a high hardness, a low friction coefficient, and a good wear resistance in unlubricated sliding experiments against alumina which make them very attractive as protective metallurgical coatings.     

The influence of Al2O3 reinforcement on the properties of stainless steel cold spray coatings

The effect of Al₂O₃ additions to type 316 austenitic stainless steel cold spray coatings was studied. Adding Al₂O₃ to the feedstock powder increased the overall deposition efficiency, though the Al₂O₃ itself deposited less efficiently than the stainless steel. Shear testing of the coatings using a shear lug test revealed a change in fracture from cohesive to adhesive with increasing alumina addition. The corrosion behaviour, assessed using anodic polarisation tests of the coatings, showed a shift towards the polarisation behaviour of bulk stainless steel with Al₂O₃ additions. All of these changes in coating behaviour with Al₂O₃ additions suggest an improved degree of metallurgical bonding, likely due to increased plasticity in the stainless steel particles.     

Thermal-sprayed Fe-10CM3P-7C amorphous coatings possessing excellent corrosion resistance

An alloy of Fe-10Cr-13P-7C was thermally sprayed by three different processes: (1) 80 kW low-pressure plasma spraying (LPPS), (2) high-velocity oxyfuel (HVOF) spraying, and (3) 250 kW high-energy plasma spraying (HPS). The as-sprayed coating obtained by the LPPS process was composed of an amorphous phase. In contrast, the as-sprayed coatings obtained by the HVOF and HPS processes were a mixture of amorphous and crystalline phases. The as-sprayed coatings showed a high hardness of 700 DPN. A very fine structure composed of ferrite, carbide, and phosphide was formed, producing a maximum hardness of greater than 1000 DPN in the LPPS coating just after crystallization on tempering. The corrosion re-sistance of the amorphous coating was superior to a SUS316L stainless steel coating in 1N H₂SO₄ solution and 1N HC1 solution. Furthermore, the amorphous coating underwent neither general nor pitting corro sion in1NUCI solution and 6% FeCl₃ 6H₂O solution containing 0.05N HCl, whereas the SUS316L stain less steel coating was attacked aggressively.     

Untersuchung der Eigenschaften von nach einem neuen Verfahren hergestellten Phosphatüberzügen

Investigation into the properties of phosphate layers obtained according layers obtained according to a new process Phosphate coatings were obtained by anodic phosphatizing in sodium phosphate solutions (2.5-5% phosphate, PH 4.2-5.4, current density 2.5-5.0m Amps/cm²). The coatings (coating weight 7.3–20 g/cm₂) consist of ferrous/ferric phosphates, the Fe²⁺: Fe³⁺ ratio depending from bath composition. he hardness of the coatings is lower than the hardness of coatings from Zn and Mn phosphate baths and their absorption capacities for chromic acid, mineral oil and paints are higher because of their fine crystalline structure. With respect to corrosion behaviour they are superior in NaCl and equivalent to Zn and Mn phosphate coatings in moist atmospheres, while the latter seem to be superior in the salt spray seem to be superior in the salt spray test. The minimum coating thickness required for subsequent painting is 8/m² subsequent oil impregnation or cold working require higher weight.     

The Effect of Water Vapor on the Oxidation Behavior of CVD Iron-Aluminide Coatings

The oxidation behavior of iron-aluminide coatings, Fe₃Al or (Fe,Ni)₃Al, produced by chemical-vapor deposition (CVD) was studied in the temperature range of 700–800°C in air + 10 vol.% H₂O. A typical ferritic steel, Fe–9Cr–1Mo, and an austenitic stainless steel, 304L, were coated. For both substrates, the as-deposited coating consisted of a thin (<5μm), Al-rich outer layer above a thicker (30–50 μm), lower-Al-content inner layer. In addition to coated and uncoated Fe–9Cr–1Mo and 304L, cast Fe–Al model alloys with similar Al contents (13–20 at.%) to the CVD coatings were included in the oxidation exposures for comparison. The specimens were cycled to 1000 1 hr cycles at 700°C and 500 1 hr cycles at 800°C, respectively. The CVD coating specimens showed excellent performance in the water-vapor environment at both temperatures, while the uncoated alloys were severely attacked. These results suggest that an aluminide coating can substantially improve resistance to water-vapor attack under these conditions.     

Effect of remelting process on characterization of air-plasma sprayed Fe67.5Ni23.5B9 alloy coatings onto 1Cr18Ni9Ti stainless steel

To develop a composite material with good mechanical and radiation shielding properties, the Fe–Ni–B (Fe_67.5Ni_23.5B₉, wt. %) coatings onto ₁Cr₁₈Ni₉Ti stainless steel substrate (SS, same as below) were prepared using air-plasma spraying (APS) technique in this work. A remelting process (1050 °C/2 h) was performed on the Fe–Ni–B coatings laminated composite under vacuum condition. The microstructure, phase composing, adhesion strength, Vickers hardness distribution and residual stress of Fe–Ni–B coatings before and after the remelting process were contrastively characterized. The results show that the remelting process decrease the coating defects and make the coating more cohesive and stable. The element diffusion and new compounds formation within the coating and interface area improves the adhesion and thermal fatigue of Fe–Ni–B coatings. In addition, the drop of variability of Vickers hardness data and residual stress level qualitatively identify that the Fe–Ni–B coatings possess more consistent microstructure and mechanical integrity after the remelting process.     

Production of LaPO4 coatings using a novel ultrasonically-assisted plating technique

Dense LaPO₄ and LaPO₄-Al₂O₃ coating films were produced on the surface of stainless steel substrates at room temperature and ambient pressure with the aid of a novel ultrasonic-based mechanical coating method, which we call UMCA. The main emphasis was on examining the conditions necessary for the successful coating operation and characterizing the as-deposited coatings for the thickness, uniformity and surface morphology. The experimental results suggested that hardness and thermal conductivity of balls and substrate are key parameters influencing the coating efficiency. The coated samples showed an improved hot corrosion resistant in Na₂SO₄-NaCl molten salts at 950 °C.     

激光比能对Fe2B激光熔覆涂层微观组织与性能的影响

利用粉末喷射激光熔覆以球形硼铁粉末为原材料成功制备了 Fe₂B 金属间化合物涂层。 采用金相显微镜 (OM)、 X 射线衍射仪 (XRD)、 扫描电镜 ( SEM)、 电子探针 (EPMA)、 显微维氏硬度计及摩擦磨损试验机对涂层的组织与性能进行了表征。 结果表明: 当激光比能控制在 3. 00×10 ⁸ kJ/ m ² 左右时, 采用粉末喷射激光熔覆能制备较为理想的 Fe₂B 金属间化合物涂层。 制备的单层涂层的物相为 Fe₂B 与 Fe, 显微硬度峰值达 1360 HV_{0. 05} , 涂层组织中大量弥散分布的 Fe₂B 相的生成是涂层具有高硬度的原因。 制备的多层涂层与基体具有良好的冶金结合, 从基体到涂层, 组织经历了一个由平面外延生长组织到胞状晶再到等轴晶的演变过程, 涂层稳定摩擦因数为 0. 385, 磨损率为 5. 67×10 ^-15 m ³ / N·m,表现出良好的耐磨性能, 磨损机制为磨粒磨损与疲劳磨损。     

Nanoscratching deformation and fracture toughness of electroless Ni-P coatings

In the present investigation electroless Ni-P coatings were prepared. Structural characterizations indicated that the as-deposited coating had an amorphous structure with a P content of 23 at.%. The deformation behavior of an electrolessly amorphous Ni-P coating was investigated by using the Vickers indentation and the Tribo-indenter instrumented nano-indentation technique. The hardness of the Ni-P coating is remarkably improved after proper heat-treatment and the hardness is as high as 12.7 GPa for the coating annealed at 400 °C for 1 h. However, the cracks were observed during the indentation of the Ni-P coatings annealed at 400 °C and 500 °C for 1 h. The corresponding fracture toughness was evaluated as 2.58 MPa m^0.5 and 1.33 MPa m^0.5, respectively. Nanoscratching tests indicated that the wear resistance of the Ni-P coatings was improved significantly with an increasing ratio of hardness (H) to elastic modulus (E). It was observed that the friction coefficient increased from 0.083 ± 0.006 for the Ni-P coating annealed at 300 °C up to 1.337 ± 0.009 for the IF steel substrate, while the H/E simultaneously decreased from 0.084 (10.7/128) to 0.009 (1.85/200). The study revealed that the electrolessly amorphous Ni-P coating had offered better corrosion resistance than the Ni-P coatings after heat-treatment. An annealing temperature of 300 °C is preferentially suggested for the trade-off between the wear resistance property and anti-corrosion property of the Ni-P coating.     

Effect of prior conversion treatment on high temperature oxidation behaviour of ceramic coated 17Cr ferritic stainless steel

Abstract

Convers(on coatings modified by deposits of alumina or zirconia have been studied as a way of improving the resistance to thermal oxidation of a 17Cr ferritic stainless steel. Conversion coatings, characterised by high porosity, facilitate the electrochemical deposition of alumina or zirconia layers and enhance their adhesion to the substrate. The resulting coats, after heating, possess compositional gradients which are favourable to strong adhesion. Alumina coatings are more effective than zirconia coatings in suppressing thermal oxidation of the steel.     

The corrosion and wear behavior of TiN and TiAlN coated AISI 316 L stainless steel

In this study, TiN and TiAlN coatings were deposited on AISI 316 L stainless steel substrates by PVD techniques. The composition and crystalline structure of the as-deposited coatings were analyzed by energy dispersive X-ray analysis (EDX) and X-ray diffraction (XRD) methods, respectively. The corrosion resistance studies of TiN-coated and TiAlN-coated samples were carried out in 0.9 wt % NaCl and SBF solutions using the electrochemical potentiodynamic polarization method and the wear behavior was evaluated with the ball-on-disk wear method at a sliding speed rate of 0.3 m/s under 2.5 N load in a dry medium. It was found that both TiN and TiAlN coatings exhibited relatively good corrosion resistance, however, TiAlN coatings showed a better corrosion resistance than TiN coatings. The TiAlN coating contributes positively against corrosion and wear behavior by increasing the surface hardness and by decreasing the friction coefficient of AISI 316 L stainless steel, respectively.     

煤油流量对HVOF铁基非晶涂层组织与性能的影响

以工业原材料制备的FeCoCrMoCBY非晶粉末为喷涂材料,采用超音速火焰喷涂(HVOF)制备铁基非晶合金涂层。通过X射线衍射仪(XRD)、差示扫描热仪(DSC)、扫描电子显微镜(SEM)、维氏显微硬度计等测试方法,探讨煤油流量对涂层显微组织、微观结构及显微硬度的影响,并分析涂层与316 L不锈钢在1 mol/L HCl溶液中的动态极化特征。结果表明:涂层与基体结合良好,呈现典型的层状结构,非晶含量高,表现出比316 L不锈钢更高的耐腐蚀性能。其它参数一定时,煤油流量越高,涂层致密度越高,非晶含量先增多后减少,显微硬度先增大后减小;当氧气流量为50 m~3/L,煤油流量为26 L/h时,涂层非晶含量最高,为99.4%,孔隙率为1.51%,自腐蚀电流密度低,为5.62×10~(-6) A/cm~2,自腐蚀电位为-0.36 V,耐腐蚀性能表现最佳。