Cr12MoV钢盐浴渗钒后的组织及耐蚀性能

目前,对Cr12Mo V盐浴渗钒层的耐蚀性鲜有研究。采用自配的混合盐对Cr12Mo V钢在不同温度和时间进行盐浴渗钒处理。通过表面显微硬度测试、金相显微和SEM形貌观察、EDS和XRD分析表征了Cr12Mo V渗层性能与组织结构,选定了较佳渗钒的温度(1 000℃)和时间(6 h),对最优工艺渗件在3.5%Na Cl溶液中进行了电化学测试,以检验渗层的耐蚀性。结果表明:Cr12Mo V钢渗钒后形成了致密的渗层,表面硬度从渗钒前的713HV3 N提高到1 800~2 700 HV3 N;渗层厚度分别与渗钒温度和保温时间成正比关系;最优工艺渗钒后的耐蚀性比渗钒前提高了36%。     

金属陶瓷覆层-钢基体界面结合状态的研究

为提高钢基材料的耐磨性和耐腐蚀性,以金属Mo粉、Fe粉和B-Fe合金粉末为原料,采用原位反应真空液相烧结技术,在钢基体表面制备三元硼化物金属陶瓷覆层.测定了覆层-钢基体界面结合强度及界面结合区的显微硬度变化,研究了界面微观结构和界面区元素分布,并对覆层-钢基体界面层形成的机理进行了分析.结果表明,覆层与钢基体之间的断裂破坏发生于界面附近的钢基体和覆层内,而不是覆层与钢基体之间结合界面的剥离;在覆层-钢基体结合界面处,存在由高硬度覆层到低硬度钢基体的狭窄过渡区,合金元素的分布形成具有一定厚度的过渡层.     

大面积、薄覆层钛/钢复合板爆炸-轧制工艺研究

探索了大面积、薄覆层钛/钢复合板生产工艺.分析了不同的轧制温度下爆炸-轧制钛/钢复合板的性能和组织.结果表明,配制低爆速混合炸药,在覆层与基层之间增加一层纯铁过渡层,采用合适的爆炸复合工艺制得轧板复合板坯,再在适当的热轧温度下轧制,可获面积超过35 m2、覆层厚度≤2.0 mm的钛/钢双金属复合板且各项性能指标符合国家标准要求;此项研究填补了国内空白,满足了市场需求.     

Q235钢固体粉末渗硼及渗层生长动力学行为

各类材料渗硼工艺不同,硼的扩散也不同,其中有许多现象往往不能定量分析.采用固体粉末法对Q235钢进行了渗硼,得到的渗硼层为锯齿状,垂直于钢表面楔入基体.用sigma Plot 10.0软件对试验数据进行了分析和拟合,得出了渗硼层等厚度图,为制定渗硼工艺提供了依据:利用此图,既可以对设定的渗硼时间和温度预测渗硼层厚度,又可以用一定的固体渗硼厚度值确定渗硼时间和温度.通过动力学研究得到了渗层相组成为单一的Fe2B相硼,在不同温度下的扩散速率常数:K800℃=1.074×10-13m2/s,K850℃=1.622×10-13m2/s,K900℃=3.921×10-13m2/s,平均扩散激活能为134.473 kJ/mol.     

Cr12MoV钢表面化学热处理的研究进展

Cr12MoV钢是国内使用最广泛的高碳高铬莱氏体型冷作模具钢,优良的表面处理工艺是保证其高强度高寿命的前提,本文概述了Cr12MoV钢的渗氮、渗硼、渗钒表面化学热处理工艺,以及不同工艺处理下Cr12MoV钢的微观组织结构和性能的改变,阐述了Cr12MoV钢化学热处理的研究现状及发展趋势。     

液体渗氮工艺对CrNiMo钢渗层厚度和硬度的影响

为了探讨无毒液体渗氮工艺对CrNiMo钢渗层的效果,采用正交试验方法研究了氮化温度、氮化时间和尿素添加量对CrNiMo钢液体渗氮层的脆性、渗层厚度和硬度的影响.结果表明,尿素添加量是影响渗层脆性和硬度的主要因素,氮化时间是影响渗层厚度的主要因素,氮化温度对渗层厚度和硬度的影响较小.最优渗氮工艺为570℃,氮化时间5 h,尿素添加量为50 g/h,此时渗层厚度为0.235mm,最高硬度为920HV,脆性级别为1级.     

Q235钢表面氩弧热源熔覆镍基自熔合金层的组织及性能

目前,鲜见氩弧熔覆镍基合金粉末工艺参数对熔覆层表面耐磨性能影响的研究报道,先将镍基自熔合金粉末涂覆于Q235钢表面,再利用氩弧热源熔覆.采用金相显微镜观察熔覆层表面和截面组织,采用硬度计及磨损试验分析熔覆层的表面硬度及耐磨性,研究了涂覆层厚度、熔覆电流对熔覆层表面组织、力学性能的影响.结果表明:基体与熔覆层形成了良好的冶金结合;随熔覆电流的增加,熔覆层表面硬度和耐磨性先增加后降低;随涂覆层厚度的增加,熔覆层表面硬度和耐磨性随之增加;涂覆层厚3 mm,熔覆电流为180 A时,熔覆层表面金相组织为少量初生固溶体枝晶和大量奥氏体与碳、硼化物的共晶,熔覆层表面硬度最大,为45.0 HRC,耐磨性最好.     

不同电源等电位离子钨钼共渗的研究

利用脉冲单电源和直流单电源,分别在Q235钢表面进行等离子钨钼共渗.通过对不同电源钨钼共渗试样的渗层组织、渗层成分分布、晶体结构、渗层硬度分布的检测和比较,分析了2种电源对等离子钨钼共渗的影响.结果表明,利用单一电源均可在Q235钢表面形成明显反应扩散层;在相同工艺下,采用脉冲电源所得到的试样渗层厚度较采用直流电源的渗层厚度增加了18.1%;脉冲电源试样表面W、Mo含量(质量分数,下同)分别约为8.4%和9.8%,直流电源试样表面W、Mo含量分别为8.2%和8.9%,可见2种电源渗层表面含W、Mo量相差不大;2种电源渗层相结构均为Fe_7W_6和Fe_3Mo金属间化合物相;钨钼共渗后渗层硬度提高不明显.     

不同Ni60-SiC比例及厚度等离子熔覆层的组织及性能

为了提高热锻模具的使用寿命,以W6Mo5Cr4V2为模具钢,在其表面通过等离子熔覆制备了Ni60-SiC金属陶瓷层.用X射线衍射仪对不同Ni60-SiC配比及厚度的熔覆层进行了物相鉴定;用光学显微镜对熔覆层的显微组织进行了分析,用维氏硬度计测定了熔覆层的显微硬度.结果表明:熔覆层厚度为3 mm、Ni60-25%SiC混合粉末所得熔覆层具有最好的冶金结合和最佳的显微硬度.     

渗硼层与渗氮层深度的测定

以H13钢的渗氮层和渗硼层为例，借助于光学显微镜、扫描电镜(SEM)、显微硬度计和X射线衍射(XRD)，分析了两者组织形态和硬度梯度上的差别，指出了两者渗层深度不同的界定标准。即渗硼层厚度的测量不能将过渡层记入渗硼层厚度，而应采用硼化物齿峰和齿谷的统计算术平均值得到渗硼层厚度。     

Sliding wear evaluation of various coating processes on AISI 52100 and M 50 steels

Abstract

Lubricated sliding wear tests were carried out on various surface coatings that were deposited on AISI 52100 and M50 steel substrates. The coatings include titanium nitride (TiN) deposited via an ion plating process, an electroplated chromium termed thin dense chrome (TDC), and a vanadium carbide (VC) deposited via the Toyota diffusion (TD) process. The tests were carried out using a synthetic turbine oil at one sliding speed and stepwise loading until catastrophic failure of the coating occurred. Friction coefficients were measured throughout the test interval, which showed that the vanadium carbide coating produced the lowest values (less than 0·055). Furthermore, this coating process had the greatest load carrying capacity, followed by the ion plated TiN on the M 50 substrate. Optical and scanning electron microscopy revealed that each coating process exhibited a different wear mode. In the TiN and VC coatings, polishing occurred along with the formation of cracks perpendicular to the sliding direction. Portions of the TiN coating spalled off the substrate via a delamination process. The TDC coating exhibited only a polishing wear mode.

MST/1691     

Corrosion Behavior of Vanadium Carbide Coating Produced by a Thermal Diffusion Process

Vanadium carbide coating was deposited on carbon steel (EN9) and mild steel using a thermal diffusion process. Samples were immersed in a molten salt bath containing appropriate carbide forming compounds at temperatures ranging from 850°C to 1100°C. Samples were treated for various lengths of time in order to obtain coatings of various thicknesses. The corrosion behavior of the vanadium carbide coatings was evaluated by accelerated electrochemical tests. The corrosion resistance of the carbide coating was found to be superior to that of the untreated base alloys.     

溅射气压对碳化钒薄膜微结构与力学性能的影响

采用碳化钒靶的磁控溅射方法在不同的Ar气压下制备了一系列碳化钒薄膜,利用能量分析光谱仪,X射线衍射,扫描电子显微镜,原子力显微镜和微力学探针研究了气压对薄膜成分、相组成、微结构以及力学性能的影响。结果表明磁控溅射VC陶瓷靶可以方便地制备晶体态的单相碳化钒薄膜,并且溅射气压对薄膜的化学成分、相组成、微结构以及相应的力学性有较大的影响。在溅射气压为2.4~3.2 Pa的范围内,可获得结晶程度好和硬度与弹性模量较高的碳化钒薄膜,其最高硬度和弹性模量分别为28,269 GPa。低的溅射气压(0.32~0.9 Pa)下,所得薄膜结晶较差且硬度较低;过高的溅射气压(>4.0 Pa),薄膜的溅射速率降低,结晶变差,其硬度和弹性模量亦随之降低。低气压下薄膜碳含量较高和高气压下溅射原子能量降低可能是薄膜结晶程度降低的主要原因。     

Microstructural and tribological characterization of laser surface engineered VC coating on tool/die steel

A successful effort has been made to deposit vanadium carbide on AISI H13 steel using Nd:YAG laser. A search for an ideal coating and equally suitable coating method for various applications will always be an interesting and challenging area in surface engineering. In the present study, a continuous, adherent, crack-porosity-free coating—composite in nature—has been obtained, which can serve as a protective tool for various surfaces. To explore the properties of this coating in greater detail, it has been evaluated for chemical, structural, mechanical, and tribological properties. It shows very high hardness and excellent wear resistance as compared to substrate H13 steel.     

Growth morphology and mechanism of primary TiC carbide in laser clad TiC/FeAl composite coating

TiC-reinforced FeAl intermetallic matrix composite (IMC) coatings were fabricated on substrate of 1Cr18Ni9Ti stainless steel using laser cladding. X-ray diffraction (XRD) was used to identify the phases in the laser clad composite coating and the growth morphologies of TiC carbide were observed by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results showed that there are two phases in the laser clad composite coating: TiC and FeAl intermetallic matrix alloy. The primary TiC carbide in laser clad coating nucleates heterogeneously on the surface of oxide particles; its growth morphology is found to be in a unique radial-branching dendrite with strongly faceted feature. The growth mechanism of TiC is confirmed to be lateral growth from the ledges or steps existing on the growing fronts.     

A two-component preceramic polymer system for structured coatings on metals

A liquid polysiloxane system consisting of a polymethoxymethylsiloxan and a hydroxy-terminated linear polysiloxane was used as preceramic polymer coatings on stainless steel. Interface reactions between the polymer derived ceramic matrix and the steel substrate were evaluated during and after pyrolysis with X-ray diffraction analysis and energy dispersive X-ray analysis. The system was loaded with different fillers and the rheological behaviour was investigated with respect to the coating thickness evolution by dip coating processing. Interface reactions with the steel components such as carbide formation and spinel formation were detected in the filler-free system and shear thinning was found to be a useful tool for coating thickness adjustment.     

A Study on Wear Failure Analysis of Tungsten Carbide Hardfacing on Carbon Steel Blade in a Digester Tank

This paper addresses wear failure analysis of tungsten carbide (WC) hardfacing on a carbon steel blade known as the continuous digester blade (CD blade). The CD blade was placed in a digester tank to mix ilmenite ore with sulphuric acid as part of a production process. Tungsten carbide hardfacing was applied on the CD blade to improve its wear resistance while the CD blade was exposed to an abrasive and acidic environment. Failure analysis was carried out on the hardfaced CD blade in order to improve its wear resistance and lifetime. A thickness and hardness comparison study was conducted on worn and unworn specimens from the CD blades. The carbide distribution along with elemental composition analysis of the hardfaced CD blade specimens was examined using scanning electron microscopy and energy-dispersive spectroscopy. The investigation revealed that an inconsistent hardfacing thickness was welded around the CD blade. Minimum coating thickness was found at the edges of the blade surfaces causing failure to the blades as the bare carbon steel blades were exposed to the mixed environment. The wear resistance of the CD blade can be improved by distributing the carbide uniformly on the hardfaced coating. Applying extra coating coverage at the critical edge will prevent the exposure of bare carbon steel blade, thus increasing the CD blade lifetime.     

钴基合金-碳化钨复合涂层耐磨抗蚀性能研究

采用真空熔烧法制得钴基合金-碳化钨复合涂层.应用盘销式摩擦磨损试验机对不同碳化钨含量的复合涂层和淬火态45#钢进行了磨损试验.借助自设计振动装置,在10%HCl溶液及10%NaOH溶液中进行了室温全浸泡振动腐蚀试验.试验结果表明,复合涂层的耐磨性显著高于淬火钢,且其耐磨性随碳化钨含量的增加而提高,复合涂层在腐蚀液中耐蚀性也远高于45#钢.     

N_2流量对车用钢表面磁控溅射CrTiAlN涂层性能的影响

目前,关于N_2流量对磁控溅射CrTiAlN涂层性能影响的研究不多。在SDC99冷作模具钢表面以不同N_2流量条件磁控溅射CrTiAlN涂层,采用扫描电镜、X射线衍射仪、显微硬度仪、显微镜和摩擦磨损试验分析涂层性能。结果表明:随着N_2流量的降低,涂层中Cr元素含量也随之下降,而N元素含量则逐渐增大,CrN(211)晶面的衍射峰缓慢增加,而CrN(200)衍射峰明显增加;CrTiAlN涂层硬度较基材提高约25%,随N_2流量降低,涂层的硬度逐渐增大;在60 m L/min的N_2流量下制备的CrTiAlN涂层和基体间结合力最佳,涂层对表面磨粒磨损情况起到最佳改善效果,此时磨痕的"犁沟"深度与宽度都减小,涂层耐磨性得到显著提高。     

The Influence of Vanadium Microalloying on Voids Occurence in Low-Alloyed Cr-Mo Steels After Continuous Casting

We discuss the correlation between segregation of carbide forming elements (vanadium) and void initiation and propagation in low-alloyed Cr-Mo steels. The internal defects are created during blooms straightening in radial type of casting machine due to strain deformation field in the temperature range characteristic for vanadium nitride, carbide or carbonitride precipitation. Based on the statistical analysis (1097 continuously cast blooms) of three low-alloyed Cr-Mo steel variants with different vanadium content, we conclude that the void occurence is strongly associated with the level of vanadium content. The experiments performed by means of microstructural, fractographic investigations and microchemical point analysis proved that preffered areas for void initiation are interdendritic segregations in the core of bloom. We observed vanadium carbide precipitates that are situated close to the cracks, whereas the content of vanadium was 7,5 times more then in an average smelt composition. The further development of defects is connected with fast heating up to the austenization temperature in soaking pit. Our results confirm that marked decrease of defects can be achieved by optimization of production process, i. e. optimized casting speed, steel overheat above the liquidus temperature and/or application of M-EMS.