P20模具钢表面合金化组织与性能

在P20模具钢表面进行激光合金化,利用金相显微镜、维氏硬度计等设备检测了合金化层的组织和性能。试验表明,激光合金化可在材料表面获得组织致密,晶粒细化,深度大,与基体结合牢固的强化层。合金化区的硬度范围为635～699HV0.2,热影响区硬度范围为441～474HV0.2。激光合金化试样的耐磨损性能比预硬化的P20钢提高了35%。采用激光合金化对模具表面进行强化,将大大提高模具的使用寿命。     

The effect of solid diffusion surface alloying on properties of ZM5 magnesium alloy

In this research, solid diffusion process was used to form a diffusion alloying layer on the surface of ZM5 magnesium alloy to improve corrosion and wear resistance. It is shown that the solid diffusion layer was mainly composed of Mg–Al–Zn intermetallic compounds and Mg–Al–Zn solid solution transition zone that had more Zn and Al elements than untreated ZM5 magnesium substrate. The continued immersion test in 3% NaCl solution displayed that the diffusion-treated specimen had better corrosion resistance compared to the untreated ZM5 specimen. The polarization test indicated that the Mg–Al–Zn intermetallic compounds of the diffusion alloying layer were an effective corrosion barrier to decrease the corrosion rate for ZM5 magnesium alloy when exposed to 3% NaCl solutions. In addition, the microhardness values of the Mg–Al–Zn intermetallic compounds were much higher than those of the substrate and this would greatly contribute to the enhancement of wear resistance.     

Effect of nano-Al2O3 on erosion–corrosion behaviour of composite alloying layer under two phase flow conditions

Abstract

The present study was focused on understanding the effect of the added nano-Al₂O₃ on erosion–corrosion behaviour of composite alloying layer. The nano-Al₂O₃ reinforced composite alloying layer was prepared by duplex surface treatment, which consisted of Ni/nano-Al₂O₃ predeposited by brush plating and a subsequent surface alloying with Ni–Cr–Mo–Cu by double glow process on the surface of AISI 316L stainless steel. Current response with applied potential, potentiodynamic polarisation curve, electrochemical impedance spectroscopy and weight loss techniques were applied to evaluate the erosion–corrosion behaviour of composite alloying layer compared with the single alloying layer and 316L stainless steel under hydrodynamic conditions. Results of electrochemical measurements showed that the erosion–corrosion resistance of composite alloying layer was lower than that of single alloying layer when the rotating velocity of tested samples was below 2·51 m s^?1, whereas the erosion–corrosion resistance of composite alloying layer was higher than that of single alloying layer when the rotating velocity of tested samples above 2·51 m s^?1. The weight loss rate studies and surface analysis suggested that the dispersive undissolved nano-Al₂O₃ particles and γ′ prime (Ni₃Al) phase were helpful to improve the erosion–corrosion resistance of composite alloying layer at high rotational speed, though the γ′ prime phase was deleterious to corrosion resistance of composite alloying layer.     

Laser surface alloying fabricated porous coating on NiTi shape memory alloy

Laser surface alloying technique was applied to fabricate a metallic porous coating on a solid NiTi shape memory alloy. By laser surface alloying a 40%TiH2-60%NiTi powder mixture on the surface of NiTi alloy using optimized laser process parameters, a porous but crack-free NiTi layer can be fabricated on the NiTi substrate. The porous coating is metallurgically bonded to the substrate NiTi alloy. The pores are uniformly distributed and are interconnected with each other in the coating. An average pore size of less than 10μm is achieved. The Ni content of the porous layer is much less than that of the original NiTi surface. The existence of the porous coating on the NiTi alloy causes a 37% reduction of the tensile strength and 55% reduction of the strain as compared with the NiTi alloy. Possible biomedical or other applications for this porous surface with good mechanical strength provided by the substrate are prospective.     

Modifying the steel surface by laser heating

Methods of increasing the service properties of steel components by producing hardened modified layers on the surface using laser heating are described. It is proposed to use a combined technology based on laser alloying the steel surface with nitride-forming elements and nitriding. It is shown that laser alloying in the continuous mode results in the formation of a layer with a uniform fine-grained structure with a thickness of 600 μm in the surface layer. Subsequent nitriding eliminates the unfavourable residual stresses and increases the microhardness of low-carbon steels to 20,000 MPa, cracking resistance 1.5–1.8 times and wear resistance 1.5–3 times.     

Laser surface alloying of ferritic Fe-40Cr alloy with ruthenium

An investigation is made of the laser surface alloying of an experimental ferritic Fe-40Cr alloy with a rutherium powder coating using a continuous wave CO₂ laser. Themicrostructure and corrosion behaviour of the laser surface alloying layer and the Fe-40Cr bulk allyo were examined by means of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy, microhardness, potentiodynamic and corrosion potential measurements. The results of the microstructural examination showed that fine cellular dendrites with a ruthenium content as high as 51.84wt.% were produced by laser surface alloying. The extended solubility of ruthenium in the cellular dendrites resulted in a dramatic increase of the hardness in the laser alloying layer. Potentiodynamic and open circuit corrosion potential measurements indicated that the ruthenium-containing surface layer spontaneously passivated in hydrochloric and sulphuric acid solutions, whereas the bulk Fe—40Cr alloy remained in the active state when exposed in these reducing acid solutions.     

Gradient complex protective coatings for single-crystal turbine blades of high-heat gas turbine engines

Complex diffusion-condensation protective coatings characterized by gradient distribution of alloying elements over the thickness due to formation of a diffusion barrier layer on the surface of blades followed by deposition of condensation alloyed layers based on the Ni-Co-Cr-Al-Y system and an external layer based on a NiAl alloyed β-phase and a ZrO₂: Y₂O₃ ceramics are presented. A complex gradient coating possessing unique protective properties at t = 1100–1200°C for single-crystal blades from alloy ZhS36VI for advanced gas turbine engines with gas temperature of 1550°C at the inlet to the turbine is described. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, pp. 41–48, May, 2007.     

W-Mo-Dy三元共渗合金层的研究

采用双辉等离子渗金属技术,在20钢表面进行W-Mo-Dy三元共渗.探讨了气压、保温时间、温度对合金渗层厚度的影响,并获本试验条件下的最佳工艺参数.对合金渗层金相显微组织和形成机理进行分析;用能谱仪检测合金元素的浓度和分布;用XRD分析合金渗层物相.结果表明:在本试验条件下最佳工艺参数为气压30 Pa,保温时间4.5h,温度1020℃,获得的共渗合金层厚度约115 μm;合金渗层中W、Mo合金元素含量随到试样表面的距离增加而减少,呈梯度分布;由于稀土的较大原子半径与核外电子的极化作用使得Dy分布不规律;合金渗层的物相主要为Fe( Mo,W,Dy)、Dy2O3和少量的DyFe10Mo2等.     

Corrosion resistance of benzotriazole passivated Cu-Zn-Alshape memory alloy in artificial Ringer's solution

1 IntroductionThe shape memory alloy (SMA) is a novel func-tional material, which combines recognition behav-ior with driving capability. Among SMAs, the Ti-NiSMA possesses shape memory effect, superelastic,well wear resistance, and low elastic modulus. A…     

双辉多元共渗与电刷镀复合表面耐蚀渗镀层的研究

在20钢表面电刷镀快速Ni层作为过渡层，然后采用双层辉光离子技术将Ni-Cr-Mo-Cu合金进行多元共渗，对形成的复合镀层在5%HCl溶液中进行了电化学腐蚀性能测试，利用XRD，扫描电镀以及EDX对渗层的组织结构和合金元素及碳元素在渗层中的分布进行了分析，结果表明；预先刷镀快速Ni镀层再进行双层辉光多元渗Ni-Cr-Mo-Cu的复合渗镀层的耐蚀性能明显优于双辉多元渗Ni-Cr-Mo-Cu以及单独电刷镀Ni镀层的耐蚀性能，分析认为，由于双辉多元共渗中的温度效应，使层复合渗镀层具有较好的耐蚀性能。     

Microstructure and residual stresses in surface layer of simultaneously laser alloyed and burnished steel

The new hybrid method, which combines the laser alloying process with slide burnishing, was investigated and presented in the work. Both treatments were performed on the laser stage in one operation. The experiments were done on carbon steel alloyed with cobalt stellite. The alloying process was conducted with continuous laser CO₂, at different parameters. The single- and multiple-path processes were investigated.The microstructure, microhardness and residual stresses of surface layer after the laser alloying process and laser alloying combined with burnishing were presented. The results of the experimental studies have shown that the proposed new hybrid method allowed for the generation of compressive stresses in surface layer of the alloyed material. The structural analysis has proven that the burnishing process had caused deformation of grains in the 20–30 μm thick zone and increased microhardness of the surface zone material.The X–ray diffraction measurements of residual stresses in surface layer of the samples subjected to the alloying process and burnishing, both in cold and hot conditions, were performed. In the case of multiple-path laser alloying treatment the tensile stresses, approximately 500 MPa, were obtained at the surface. Multiple alloying combined with burnishing generated compressive stresses of about ?600 MPa at the surface, substantially improving the surface layer.     

钨钼钇等离子共渗工艺及渗层组织的研究

利用辉光等离子渗金属技术,在低碳钢Q235表面进行钨钼钇共渗,研究了极间距、保温温度、气压、保温时间对渗层厚度的影响,进而确定最优工艺参数,并对渗层的金相组织、合金元素分布及物相组成进行分析。结果表明:极间距25mm、保温温度1 000℃、工作气压30Pa、保温时间3h为最优参数,所得渗层的厚度可达37μm;渗层组织为柱状晶,渗层与基体有一明显分界线;钨、钼在渗层中呈梯度分布,钇在渗层中呈不均匀分布并在晶界处发生偏聚。     

等离子共渗W-Mo-Y工艺及渗层组织的研究

采用辉光等离子渗金属技术对Q235钢进行W-Mo-Y三元共渗,探讨了极间距、气压、保温时间、温度对共渗层厚度的影响,并分析了共渗层的金相显微组织、合金元素分布及物相组成.结果表明:在试验涉及的条件下,以极间距25 mm,气压30 Pa,保温时间3 h,温度1000℃为最佳工艺参数;共渗层主要由Fe3Mo,Fe(Mo,W...     

Verteilung einiger Elemente in der Oxidschicht eines unlegierten Stahls

Distribution of some elements in the oxide laver of an unalloyed steel In an investigation into the properties of oxide layers formed on the surface of an unalloyed carbon steel (?SN 12022) at 650 °C in CO₂ the distribution was determined of certain alloying elements and impurities in the metal and the oxide layer. The oxide layer was formed by two layers; the inner one was in most cases somewhat thicker than the external one. Between the two there were pores (up to 200pm ?) and a phase boundary. The concentration of 8 alloying elements was determined with the aid of a microprobe applied to an entire cross section. In this it was found, that Al, C, S and Cu are concentrated at the phase boundary metal-oxide, while s, Cu, Si and Mn are found predominantly at the phase boundary between the two oxide layers. These phenomena may help to solve the problem of scale blistering because the solubility of carbon and oxides of alloying elements in iron oxides is by far exceeded at the two phase boundaries.     

304不锈钢双辉等离子渗铜铪表面合金层组织及抗菌性能

利用双辉渗金属技术在304不锈钢表面进行铜铪共渗,使用光学显微镜、X射线衍射仪和扫描电镜研究铜铪共渗合金层的显微组织、相结构、形貌、成分和表面硬度,采用薄膜密贴法对合金层进行抗菌性能的检测。结果表明:铜铪共渗合金层由扩散层和沉积层构成,合金层表面组织致密、分布连续、无明显裂纹和孔隙。铜、铪含量由表至里逐渐减少,渗铜铪试样中的铬和碳都出现向渗层表面迁移的现象。抗菌检测中,铜铪合金层表面对大肠杆菌和金黄色葡萄球菌都具有优良的抗菌性能,抗菌率均达到99%以上。当铜在源极棒中比例达到80%和90%时,所得到的渗铜铪试样抗菌率分别为99.83%和99.12%,当铜比例为70%时得到渗后试样的抗菌率仅为93%。渗后试样表面硬度约为605 HV0.1,大于渗铜试样和304不锈钢表面硬度。     

Improvement of the wear resistance of titanium alloyed with boron nitride by electron beam irradiation

Surface alloying of commercially pure titanium was carried out with an electron beam (EB) apparatus using a boron nitride powder which was previously deposited on its surface by Atmospheric Plasma Spraying (APS) in order to produce a composite layer with high wear resistance.Electron beam surface alloying is an important surface engineering routine that involves melting of a pre-deposited layer or concomitantly added alloying elements/compounds with a part of the underlying substrate by direct energy electron beam irradiation to form an alloyed zone characterized by a novel microstructure and composition.The present study is concerned with the influences of EB-remelting process on the wear resistance of the alloyed titanium material. The microstructure, corrosion resistance and phase analysis were also examined. Scanning electron microscopy (SEM), light microscopy (LM) and X-ray Diffraction (XRD) were performed to characterize the phase modification and morphology after the EB treatment. The sliding wear as well as the hardness of the remelted material was significantly improved (in comparison with pure Ti) through this alloying technique. The corrosion behaviour of the modified surfaces was compared with that of Ti in order to demonstrate that its initial good corrosion resistance is not strongly influenced due to surface alloying.     

Experimental Research on 32Cr3Mo1V Substrate AntiMolten Aluminum Corrosion by Laser Treatment

Two types of layers were prepared by means of laser surface alloying process using High-power Transverse Flow CO2 laser beam with different additions,which were pure Cr powder and Co alloy powder on the 32Cr3Mo1V substrate.The unique characters of laser treatments,such as microstructure,distribution of elements,and micro-hardness were studies in thorough;furthermore,the abilities anti-molten aluminum’s corroding of the layers were tested in 700 centigrade molten aluminum.The results indicate that both laser treated layers can enforce the ability anti-corroding of the molten aluminum on 32Cr3Mo1V substrate,while the laser alloying layer with Cr powder shows the most advantage of anti-aluminum corrosion character,i.e.the layer does not be corroded at all in the corrosion experiment.And the diffused thickness of aluminum in the layers by laser alloying process with Co powder is half below that of in the 32Cr3Mo1V substrate.     

Effect of ternary alloying elements on the shape memory behavior of Ti–Ta alloys

The effect of ternary alloying elements (X = V, Cr, Fe, Zr, Hf, Mo, Sn, Al) on the shape memory behavior of Ti–30Ta–X alloys was investigated. All the alloying elements decreased the martensitic transformation temperatures. The decrease in the martensitic transformation start (M_s) temperature due to alloying was affected by the atomic size and number of valence electrons of the alloying element. A larger number of valence electrons and a smaller atomic radius of an alloying element decreased the M_s more strongly. The effect of the alloying elements on suppressing the aging effect on the shape memory behavior was also investigated. It was found that the additions of Sn and Al to Ti–Ta were effective in suppressing the effect of aging on the shape memory behavior, since they strongly suppress the formation of ω phase during aging treatment. For this reason the Ti–30Ta–1Al and Ti–30Ta–1Sn alloys exhibited a stable high-temperature shape memory effect during thermal cycling.     

Ti6Al4V钛合金表面激光合金化制备Ti-Cu合金层的组织结构

采用激光合金化技术在Ti6Al4V合金基体表面制备了厚度约为120 μm均匀致密连续的Ti-Cu合金层,分析了合金层的元素分布和显微组织结构。结果表明,Ti-Cu合金层中Cu元素随着合金层深度呈梯度分布,在靠近Ti-Cu合金层表面的区域主要是柱状晶夹杂着少量的块状晶,中上部区域主要是生长取向各异且较粗的不发达枝状晶和部分胞状晶,中下部区域主要是生长取向各异的胞状晶,合金层与基材的界面处主要以细小的平面晶为主。合金化层中Cu元素和Ti元素除了形成固溶体外,还形成了Ti₂Cu、Ti₃Cu和Cu₃Al₄等金属间化合物,同时还形成了Cu₃TiO₄和Al₂TiO₅等金属陶瓷相。     

Alloying effects on properties of Al2O3 and TiO2 in connection with oxidation resistance of TiAl

In the present work, a first-principles method is used to calculate the oxidation energies of Al₂O₃ and TiO₂ as well as the formation energy of oxygen vacancy in TiO₂ containing various alloying elements, in order to shed some light on the alloying effects on the oxidation resistance of γ-TiAl. Our calculations demonstrate that almost all alloying elements increase the oxidation energies of Al₂O₃ and TiO₂. The alloying elements with number of d electrons from 2 to 5 in the forth and fifth rows of the periodic table (e.g., Zr, Nb, Mo, Hf, Ta, W) increase significantly the oxidation energy difference between Al₂O₃ and TiO₂, i.e., reduce the relative stability of Al₂O₃ to TiO₂. On the other hand, these alloying elements increase the formation energy of oxygen vacancy in TiO₂. The effects of other alloying elements are less significant or opposite. Observing the experimental mass gains of TiAl alloys and unalloyed TiAl due to oxidation, we find that the elements reducing the relative stability of Al₂O₃ to TiO₂ and increasing the formation energy of oxygen vacancy enhance the oxidation resistance of TiAl whereas others do not. Such correlations are rationalized by analyzing the alloying effects on the internal oxidation of Al in the γ-TiAl matrix and the diffusion of oxygen in TiO₂ surface scale.