合金化渗氮的组织性能与应用

针对合金化涌氮的组织性能进行了研究，研究结果表明，合金化渗氮可形成高硬度，低脆性和致密的渗层；４０Ｃｒ钢合金化参氮后的接触疲劳强度与常规气体氮碳共渗相比提高８３．３３％。     

A source of broad electron beams with a self-heated hollow cathode for plasma nitriding of stainless steel

The principle of operation and characteristics of a broad electron beam source based on the discharge with a self-heated hollow cathode and widened anode part are described. The source is intended for the ion nitriding of metals in the electron beam plasma. The influence of the current density (1–7 mA/cm²) and ion energy (0.1–0.3 keV) on the nitriding rate of the 12X18H10T austenitic stainless steel is studied. It is shown that the maximal nitriding rate is reached by the combining of the minimal bias voltage across the samples (100 V) and maximal ion current density, which ensures the dynamic oxide layer sputtering on the sample surface. The electron source, in which electrons are extracted through a stabilizing grid in the direction normal to the axis of the hollow cathode, ensures the radially divergent electron beam formation with a 700-cm² initial cross section, a current of up to 30 A, and initial electron energy of 0.1–0.5 keV. The source stably operates at nitrogen-argon mixture pressures of up to 3 Pa.     

Interaction of fomblin® lubricant with surface nitrided and/or coated bearing (M50) steel

High‐temperature perfluoropolalkylether lubricants including Fomblin^® are susceptible to degradation and cause corrosion in the presence of ferrous metals such as M50 bearing steel. This paper describes the effect of surface treatment (nitriding), coating chemistry and architecture in preventing corrosion/oxidation of M50 steel and thermo‐oxidative degradation of Fomblin^® fluid. Specifically, Cr‐CrN multilayered coating architecture was used with and without a nitrided steel surface. The oxidation/corrosion tests were conducted by immersing the nitrided and/or coated M50 coupons in Fomblin^® fluid in an oxidative environment at 270°C for 24 h and compared with untreated/uncoated coupons. It is shown that a considerable lessening of the corrosion of the steel and degradation of the Fomblin^® fluid can be achieved by nitriding alone. Nitriding in combination with the multilayered Cr‐CrN coating exhibited the best protection. The results are discussed in relation to the literature data. Copyright © 2009 John Wiley and Sons, Ltd.     

稀土元素对LD钢氮化过程和抗滑动磨损性能影响的研究与应用

研究了稀土元素对LD钢氮化过程和抗滑动磨损性能的影响。结果表明：稀土对LD钢的氮化过程有明显的催渗作用；稀土对氮化层的改性作用可显著提高LD钢的抗滑动磨损性能．且该作用随着时间的延长更加明显。稀土氮化工艺处理的自行车车圈轧辊模具使用寿命较普通氮化提高了一倍以上。     

稀土元素对38CrMoAl钢氮化过程催渗和性能的影响

本文研究了在气体氮化过程中添加微量稀土元素对渗入动力学过程和性能的影响。试验结果表明：稀土对38CrMoAl钢氮化过程有显著的活化催渗作用,渗速提高25%～30%;耐磨性和弯曲疲劳强度有提高;电子探针证实,在氮原子子渗入的同时,稀土La作为活性组元也渗入了钢的表层,起微合金化作用,改善了钢的性能。     

A study on the cavitation resistance of ion-nitrided steel

Cavitation is a common deterioration process of a material resulting from high-speed fluid attack. Surface treatments are usually preferably considered to promote cavitation resistance because economic reason and longer durability consideration. The cavitation behaviors of ion-nitrided carbon steel, the response of nitriding layer to various cavitation environments, in particular, were studied. An ASTM G32-85 standard method was conducted to proceed cavitation test in fresh water, 3.5 wt.% NaCl and 3.5 wt.% HCl aqueous electrolytes, respectively.Experimental results show that nitriding of steel would reduce the cavitation rate of the S48C steel in fresh water due to the hard nitrided surface which could resist mechanical damage. Electrochemical corrosion plays a part in the case of 3.5 wt.% NaCl and 3.5 wt.% HCl electrolytes. Ion-nitrided specimens in the former electrolyte, therefore, become less protective than in fresh water with, however, lower cavitation rate than blank steel. Ion-nitrided specimen in the later electrolyte subjecting primarily to electrochemical attack to the nitriding layer, which has high corrosion current, shows inferior cavitation resistance than blank substrate. Therefore, the method of surface modification should be properly determined depending on what electrolyte would be used. Ion nitriding of carbon steel in our case is suitable for fresh water and 3.5 wt.% NaCl electrolyte, but not for 3.5 wt.% HCl electrolyte.     

渗氮GCr15钢在含氮硼酸酯添加剂润滑油作用下的摩擦学性能

针对提高滚动轴承使用寿命的问题,提出离子渗氮处理与添加剂结合的解决办法。用等离子渗氮炉在GCr15轴承钢表面制备了渗氮层,并用扫描电子显微镜(Scanning electron microscope, SEM )、X射线衍射仪(X-ray diffractometer, XRD)和显微硬度计观测了渗层的形貌、相结构和硬度变化。利用四球摩擦磨损试验机对比考察渗氮钢和未渗氮钢在含氮硼酸酯润滑条件下的摩擦学性能,并用X射线光电子能谱仪(X-ray photoelectron spectroscope, XPS)分析摩擦反应膜的成分与化学结合态。结果表明,渗氮层与润滑油添加剂之间发生了意想不到的良好交互作用,渗氮钢在质量分数为1.25%氮硼酸酯的润滑条件下表现出最低的摩擦因数和磨斑直径,比未渗氮钢分别降低了34%和45%;分析证明,渗氮层的摩擦表面生成了高BN质量分数的摩擦反应膜是获得优异摩擦学性能的主要原因,而在未渗氮钢摩擦表面未检测到BN。     

The effect of fretting on the fatigue behaviour of plasma nitrided stainless steels

The plain fatigue and fretting fatigue behaviour of a plasma nitrided dual phase stainless steel known as 3CR12 and an AISI 316 austentic stainless steel have been studied in the present work, using a modified Wohler rotating-bending configuration. Test specimens were produced at two nitriding temperatures, namely 400 and 520 °C, representing low temperature and conventional nitriding temperature, respectively. The test results demonstrate that both nitriding processes can enhance the plain fatigue limit of these steels by approximately 10-25%, with the high temperature process being slightly more effective. Under fretting fatigue conditions, the beneficial effect of plasma nitriding is even more significant and the fretting fatigue limit is increased between 50 and 100% for 3CR12 and at least 50-150% for the AISI steel as the nitriding temperature is raised from 400 to 520 °C.     

离子渗氮气氛对TC4钛合金组织与性能的影响

研究了在不同气氛下进行离子渗氮对TC4钛合金渗氮层的组织与性能的影响。进行了金相组织检查,显微硬度测定,X射线结构分析,磨损试验与渗氮层氧含量测定。试验结果表明,保温时的气氛对控制渗氮层质量有较大的影响     

Suppression of tool damage in ultraprecision diamond machining of stainless steel by applying electron-beam-excited plasma nitriding

Mirror surface machining of stainless steel with single-crystalline diamond tools is proposed in this study by applying a new nitriding method, called electron-beam-excited-plasma (EBEP) nitriding, to workpiece surfaces as pretreatment. It is well known that mirror surface finish of steel workpieces by conventional diamond cutting is unachievable owing to rapid tool wear. Nitriding of steel workpieces has been one of the several attempts to prevent the rapid tool wear of diamond tools. It has been reported that the rapid tool wear is caused by thermochemical interaction between diamond and steel, and that the wear can be greatly reduced by nitriding of steel. However, hard compounds formed on the outmost surfaces of workpieces by the conventional nitriding methods can cause micro-chippings of cutting tools. The authors has recently developed a new nitriding method called EBEP nitriding, in which a high dissociation rate for nitrogen molecules is achieved using the electron-beam-excited-plasma, and iron-compounds-free nitriding has been realized. Therefore, the EBEP nitriding is applied to a typical mold material, modified AISI 420 stainless steel, aiming at suppressing the micro-chippings as well as the thermochemical tool wear during diamond cutting of the stainless steel. The conventional ion nitriding and the gas nitrocarburizing are also applied to the same stainless steel in comparison. Chemical components of the nitrided workpiece surfaces are analyzed by an electron prove micro-analyzer (EPMA) and an X-ray diffraction (XRD) in advance, and turning experiments are conducted with single-crystalline diamond tools. Subsequently, changes in cutting forces and roughness of finished surfaces and tool damages after the turning experiments are evaluated. Finally, mirror surface machining by using the EBEP nitriding is demonstrated, and its advantages and disadvantages in the diamond cutting of stainless steel are summarized in comparison with the conventional nitriding methods.     

Wear kinetics of contact surfaces with use of C<Subscript>60</Subscript> fullerene additive to motor oil

It is shown that under nonstationary friction conditions, the wear resistance of contact surfaces increases when antifriction nanodisperse C₆₀ fullerene is added to the ESSO SAE 10w40 motor oil. The effect is attributed to a polymerization diamondlike molecular layer arising on the friction-activated metal surface, which leads to decreasing of the softening rate of the 40X steel surface layers and increasing of the hardening rate of the surface layers of SCh 32–52 cast iron.     

Multi-pass scratch test behavior of modified layer formed during plasma nitriding

316L stainless steel and Ti6Al4V alloy were plasma nitrided at different treatment parameters, and the wear behaviors of the modified layers formed on the surface during nitriding were investigated by multi-pass scratch test. Phase structure and cross-sections of modified layers were also examined with XRD and SEM. While a single modified layer formed on surface of the 316L stainless steel, both modified and diffusion layers were observed on the surface of the Ti6Al4V alloy after nitriding. As a result, it was observed that phase structure and thickness for modified layers of 316L stainless steel and Ti6Al4V alloy, respectively, were the significant parameters for friction coefficient and wear rate. In addition, diffusion layer formed during the nitriding process caused on increase of wear resistance of Ti6Al4V alloy by supporting the modified layer on the surface.     

不同热处理条件下45#钢与40Cr钢摩擦学性能比较

针对机械行业中45^#钢和40Cr钢使用混乱的状况,着眼于2种钢材的基础性能,从45^#钢和40Cr钢的耐磨性能入手,对二者在不同热处理条件下的摩擦学性能进行了研究和比较。结果表明：在调质处理状态下,45^#钢和40Cr钢与GCr15钢对磨时的摩擦因数基本相同,但45^#钢的磨损量要低于40Cr钢,在强度符合条件,工件形状不太复杂的情况下,建议采用45^#钢;在淬火加低温回火处理状态下,45^#钢的摩擦因数与磨损量均高于40Cr钢的摩擦因数。在强调工件的强度和耐磨性时,建议采用40Cr钢;在高频淬火加低温回火处理和在离子氮化处理状态下,45^#钢的摩擦因数与磨损量均接近于40Cr钢的摩擦因数与磨损量,在保证强度的情况下,可以考虑采用45^#钢以降低生产成本。     

Influence of heat and thermochemical treatment on abrasion resistance of structural and tool steels

Abrasive wear is responsible for intensive degradation of machine parts or tools. This process starts as an interaction between hard, mostly mineral, particles and the working surface. Methods of increasing the lifetime are based on application of abrasion resistant materials or creation of hard, wear-resistant surface layers or coatings on the surfaces of machine parts or tools. Carbon and low-alloy steels with different types of thermochemical treatment (case hardening, nitriding) are used in cases of low abrasion. Another method of increasing lifetime is the application of ledeburitic steels. The wear resistance of these steels depends on their chemical composition and heat treatment. The results of laboratory tests of thermochemically treated steels, heat-treated ledeburitic chromium steels and high-speed steels show the effect of the microstructure of these steels on their abrasion resistance. Abrasion resistance of carburized low-alloy steels is on the same level as in high-carbon structural and tool steels. In ledeburitic chromium steel maximum abrasion resistance was achieved by quenching from 1100 °C whilst in ledeburitic chromium–vanadium steel the optimum quenching temperature was 1150 °C. Growing abrasion resistance was caused by increasing amounts of retained austenite.     

Erosion–corrosion and corrosion properties of DLC coated low temperature gas-nitrided austenitic stainless steel

Low temperature nitriding of stainless steel leads to the formation of a surface zone of so-called expanded austenite, i.e. by dissolution of large amounts of nitrogen in solid solution. In the present work the possibility of using nitrogen expanded austenite “layers” obtained by gaseous nitriding of AISI 316 as substrate for DLC coatings are investigated. Corrosion and erosion–corrosion measurements were carried out on low temperature nitrided stainless steel AISI 316 and on low temperature nitrided stainless steel AISI 316 with a top layer of DLC. The combination of DLC and low temperature nitriding dramatically reduces the amount of erosion–corrosion of stainless steel under impingement of particles in a corrosive medium.     

Effect of hydrogen heat treatment on antifriction properties of nitrided VT6 titanium-based alloy

A comparative study of the antifriction characteristics of specimens of the VT6 titanium-based alloy subjected to nitriding without preliminary treatment and after hydrogen heat treatment has been carried out. Hydrogen heat treatment that precedes nitriding reduces the coefficient of friction of the nitrided specimens of the VT6 alloy in pair with the 12Kh18N10T stainless steel by 4–9% under dry friction and increases it by ~47% in a working fluid, which is a 0.9% NaCl solution. Hydrogen heat treatment combined with ionplasma nitriding reduces the coefficient of friction in working fluid by ~41%.     

High temperature friction and wear characteristics of various coating materials for steam valve spindle application

Various coatings such as chromium carbide (deposited by plasma spraying and detonation gun techniques), chromium oxide, chromium oxide+titania+silica, NiCrAlY, and Al₂O₃+NiAl, all deposited by plasma spraying; stelliting, and surface nitriding have been applied on X20CrMo V121 steel. This steel is used for high temperature applications such as steam turbine valve spindle. Friction and wear behavior of the surface coated and treated materials have been studied at an elevated temperature of 550°C while rubbing against graphite-filled stellited steel. These studies have been carried out on SRV Optimol reciprocating tribometer. Test parameters for tribological studies have been selected with a view to simulate operating conditions encountered in operation. Additionally, the structure, porosity, hardness, bond strength, and thermal cycling behaviour of these surface coated/treated materials have been characterised. Based on these laboratory investigations, chromium carbide coating deposited by plasma spraying technique has been identified as the most suitable coating for steam turbine valve spindle application. Process parameters have been established for deposition of chromium carbide coating by plasma spraying technique on actual valve spindles. The field results obtained are found to be commensurate with the laboratory findings.     

ESPCP系统推力球在原油态下摩擦磨损性能研究

利用SRV摩擦磨损试验机模拟了潜油螺杆泵采油系统（ESPCP系统）推力球在原油为润滑介质时的摩擦磨损性能，通过不同热处理的GCr15钢球与GCr15钢盘的摩擦磨损性能研究，考察了等离子渗氮GCr15钢代替淬火GCr15钢的可行性；利用X射线散射（XRD）对等离子渗氮GCr15钢表面进行成分分析，考察了以原油为润滑介质时，钢盘的摩擦磨损性能。结果表明，GCr15钢等离子渗氮后在提高表面硬度的同时，其抗磨性能大幅度提高。通过扫描电子显微镜（SEM）和X光电子能谱仪（XPS）对磨斑表面形貌和表面成分进行了分析，表明等离子渗氮层具有更好的抗磨、减摩性能和更高的承载能力。     

A compact pulsed X-ray source for high-speed radiography

A pulsed source of hard X rays for high-speed radiography is described. The source is composed of a line pulse transformer, which is discharged into an accelerating tube with a vacuum diode, producing a high-voltage pulse across the tube with an amplitude of up to 750 kV. The effective energy of X-ray quanta, determined by attenuation in a 5-mm-thick steel plate, is 125 keV. The X-ray dose at a distance of 1 m from the anode is 10 and 15 mR at a 40- and 60-ns full width at half-maximum of the X-ray pulse, respectively. The diameter of the X-ray emitting spot is <2 mm. Photographic images of a steel step wedge 5–15 mm thick and steel beads ≥0.5 mm in diameter have been obtained.     

模具钢表面多弧离子镀CrAlN涂层的制备及其摩擦性能研究

为了改善模具钢表面质量,采用多弧离子镀技术在H13模具钢表面沉积CrAlN薄膜,探讨H13钢基体表面渗氮处理后对薄膜表面形貌、硬度、结合力、抗氧化性和摩擦磨损性能的影响。结果表明：基体表面渗氮处理前后制备的CrAlN涂层表面均匀致密,都有少量的大颗粒,涂层表面均呈CrN（200）面择优取向,而渗氮后制备的涂层CrN（200）面择优取向更强;基体H13钢经过表面渗氮后,硬度显著提高,对制备的涂层具有支撑作用,降低了裂纹产生倾向,提高了涂层产生裂纹的临界载荷,提高了涂层的膜基结合力;相较于基体表面未渗氮处理制备的CrAlN涂层,基体表面渗氮后制备的CrAlN涂层具有更高的硬度和结合力,更为优异的摩擦磨损性能,且抗高温氧化性能显著增强。