纯氮离子渗氮工艺及机理研究

采用高电压低气压、闭炉保温的渗氮工艺对合金钢在纯氮气氛下进行离子渗氮，测定了渗氮层的硬度梯度、渗层深度和相组成。在相同的渗氮时间里，纯氮离子渗氮获得了比以氨气作为渗氮气源进行离子渗氮更好的效果。而且克服了氨气渗氮容易产生环境污染的缺点。通过对纯氮渗氮不同工艺的对比试验，发现只有在足够高的电压下才有明显的渗氮效果。分析了离子渗氮过程中阴极位降区离子的行为，也对渗氮电压如何影响活性氮原子的产生进行了定量的计算，探讨了纯氮离子渗氮的机理。     

渗氮工艺基本原理、特点及优缺点

正渗氮工艺为向钢件表面渗入活性氮原子形成富氮硬化层的化学热处理工艺,分为液体渗氮、气体渗氮和离子渗氮,按用途可分为强化渗氮和抗蚀渗氮。原理:在400℃以上,氨分子在钢表面分解出活性氮原子(2NH_3=3H_2+2[N]),氮原子被钢表面吸收,溶入固溶体,与铁和合金元素形成化合物,氮原子并向心部扩散,形成一定厚度的渗氮层。     

纯氮气氛下活性屏离子渗氮处理及其影响因素

利用活性屏离子渗氮(ASPN)技术对38CrMoAl钢在纯氮气氛下进行离子渗氮处理,对渗氮层的硬度、深度、组织结构以及收集粒子的形貌、结构等进行了分析研究.结果表明,电压较低时,Fe主要与O结合生成大量的氧化铁而不能进行ASPN处理,氧起主导作用;只有在电压较高、Fe与N的结合能力较强时才主要生成吸附大量活性氮原子的氮化铁进行ASPN处理.     

纯氮气氛活性屏离子渗氮的研究

在纯氮气氛中，利用活性屏离子渗氮(ASPN)技术对38CrMoAl钢进行了离子渗氮处理，并对渗层的组织结构、硬度、深度等进行了分析。结果表明，只有直流辉光放电电压高于800V时，在纯氮气氛中才能进行活性屏离子渗氮处理。通过对等离子放电空间的粒子进行XRD分析发现，放电电压低于800V时，沉积在基材表面的粒子主要是氧化铁(Fe3O4)；放电电压高于800V时，沉积在基材表面的粒子才是能进行活性屏离子渗氮处理的铁的氮化物(ε，γ‘)。     

40Cr钢富氮层快速离子渗氮技术的探索

用活性屏离子渗氮(ASPN)技术对40Cr钢进行快速离子渗氮技术的研究.本项研究是利用氮在奥氏体与铁素体中分别具有不同的溶解度和扩散速度的特性,采用了在共析温度以上短时间溶氮和在共析温度以下长时间扩散渗氮的两种不同的渗氮机制,进行交替渗氮处理.试验结果表明,采用这种新的渗氮工艺不仅可以显著提高渗氮处理中氮在钢中的内扩散速度,而且渗氮层具有较高的硬度.这种快速渗氮工艺可以用"吸收-扩散"渗氮模型进行解释.     

富氮层快速离子渗氮工艺及机理研究

利用正交试验法对活性屏快速离子渗氮工艺参数进行优化,并对正交试验预测的优化工艺参数进行了验证。利用Fick第二扩散定律对快速离子渗氮优化工艺的富氮层进行了氮浓度、氮浓度梯度的计算。试验及计算结果表明,高温渗氮温度、高温渗氮时间和低温渗氮时间对渗层厚度的影响较大,选择合适的参数可以在渗氮时间不变、渗层硬度不降低的前提下显著增加渗层厚度。当富氮层厚度为8μm时,采用快速渗氮技术得到试样内表面与基体之间的氮浓度梯度,为传统渗氮模式的20倍以上。     

循环氮势快速离子渗氮

研究了循环氮势快速离子渗氮工艺机理和方法。对４０Ｃｒ和３８ＣｒＭｏＡｌ钢进行了离子湖氮。结果表明,与常规离子渗氮工艺相比,该工艺能显著地增加材料的渗氮层深度和耐磨性。     

纯氮气氛下铜制活性屏离子渗氮试验

铁-氮化合物微粒被认为是活性屏离子渗氮过程中活性氮原子的主要输运载体,试验采用既不吸附氮也不与氮反应生成化合物的铜制活性屏和纯氮气氛,在没有铁-氮化合物微粒的情况下,对45钢试样进行渗氮处理.结果表明,在此条件下,45钢存在渗氮层,渗氮过程除依托铁-氮化合物输运外,活性氮原子还有其它重要的不可忽视的输运方式.     

稀土Ce和C原子对20CrMnTi钢渗氮层的影响

通过在离子渗氮炉的阴极盘上放置少量的稀土Ce和椰壳活性炭C,采用循环变温工艺对调质后的20Cr Mn Ti钢进行离子渗氮。设计了几种渗氮工艺作为对比,经过试验和检测发现:同时加入稀土Ce和活性炭的离子渗氮工艺处理后的试样渗氮层厚度和表层硬度明显高于单独加稀土Ce或活性炭的工艺;稀土Ce能够同时促进C和N原子在20Cr Mn Ti钢中的扩散速度;C原子的加入有助于20Cr Mn Ti钢中ε相的增多,而稀土Ce的加入却阻碍了ε相的增多;     

国内外渗碳和渗氮热处理工艺的新进展（三）

5活性屏离子的渗氮技术 [22-26]钢铁工件渗氮的典型处理温度为450~590℃,一般工件处于铁素体或铁素体＋渗碳体状态。依靠辉光放电的离子渗氮技术自上世纪70年代以来已获得愈来愈广泛的应用,但气体渗氮和盐浴渗氮（硫碳氮共渗）仍占65%的比例。离子渗氮过程中工件的打弧和空心阴极效应以致损坏处理工件表面是必须予以克服的。5.1离子渗氮过程中氮传递的本质T.Bell等1987年综述了这个问题,Ederihofer和Keller等认为由于离子轰击使工件表面溅射出来的原子和气氛中的活性氮原子结合沉积,后来,     

氮势控制技术及其应用

简要介绍了渗氮机理及氮势控制技术，并在GN70／120型井式渗氮炉内进行了可控渗氮试验。结果表明，采用HydroNit氢探头能精确测量和控制炉内氮势，有效降低渗层氮浓度，减少表面白视层厚度，满足高质量渗氮要求。     

High frequency and low voltage plasma immersion ion implantation of nitrogen on industrial pure iron at different Rf power

Traditional plasma ion immersion implantation (PIII) can effectively improve material mechanical property and corrosion resistance. But the modified layer by PIII is too thin for many industrial applications. High frequency and low voltage plasma immersion ion implantation (HLPIII) has advantages of PIII and nitriding. Comparing with traditional ion nitriding, HLPIII can obtain higher implantation energy and create a thick modified surface layer. In the present paper nitriding layers were synthesized on industrial pure iron using high frequency and low voltage plasma immersion ion implantation with different RF power (400 W, 600 W, and 800 W). The microstructure of the nitriding layers was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The mechanical properties such as microhardness and wear resistance were analyzed using HXD1000 microhardness and CSEM pin-on-disk wear testing machine. The anodic polarization characteristics were measured in a 0.9% NaCl solution at room temperature to examine the corrosion resistance of the nitriding layer. The results reveal that Fe₂N, Fe₃N and Fe₄N coexist in the nitriding layer. The nitriding layer is a corrosion protective coating on industrial pure iron in 0.9% NaCl solution. The hardness, wear resistance and corrosion resistance of the nitrided layers on industrial pure iron increase with RF power.     

氮等离子焰纯钛表面氮化

利用改造TIG焊枪通入N2+Ar混合气体产生氮等离子焰,在大气中直接加热纯钛试件,使基体表面的Ti元素与等离子焰中的N元素相互作用形成氮化层.主要研究了氮化温度和氮化时间对纯钛表面氮化层组织及性能的影响规律,得到了较佳氮化工艺参数.采用金相显微镜、扫描电镜和X射线衍射等检测方法,分析了氮化层的形成机理、表面及截面微观形貌,并测试了表面显微硬度及耐磨性.结果表明,氮化层主要由TiN相组成,组织均匀、致密,与基体为良好的冶金结合,有效地改善了纯钛基体的耐磨性.     

40Cr钢氮气/甲烷离子氮碳共渗后的组织和耐磨性

用金相显微镜和X射线衍射仪研究了40Cr钢经氮气／甲烷离子氮碳共渗后的显微组织和微观结构。在HQ-1型摩擦磨损试验机上进行了耐磨性试验，并与普通氨气离子渗氮结果进行比较。结果表明：40Cr钢经氮气／甲烷离子氮碳共渗处理后，表层获得了由Fe3C和Fe3N组成的化合物层，摩擦系数降低，失重减少，明显提高了40Cr钢的耐磨性能,磨损痕迹只有轻微擦伤。     

Solid Solution Nitriding Technology of 15Cr-7.5Mn-2.6Mo Duplex Stainless Steel

NEW DEVELOPMENT of stainless steel mainlyoccurs in area of nitrogen-containing austenitic steeland austenitic-ferritic duplex steel.It has been proposedthat a nitrogen-alloyed steel can be considered as anhigh nitrogen steel(HNSs),when the nitrogenconcentration is higher than0.4wt%in austenitic steelsand higher than0.08wt%in martensitic steels'M1.Butthis concept has been developed for the newmanufacturing technologies of HNS,such as pressureor powder metallurgy.In addition,the chemical…     

节能和高效率的离子渗氮炉设计

针对国内离子渗氮炉使用中常见的问题,从减少炉壁散热损失、增加底座承重能力、提高电极连接可靠性等方面提出了改进设计方案.新的设计中取消了大部分的炉壁冷却水夹层,增加了真空隔热层,升温时减少热量损失,降温时充入氮气强制对流冷却,配合快速冷却装置,增加导热系数,加快工件冷却速度.采用圆弧型封头底座,增大炉体承重能力,并改善气体流动的均匀性.输电阴极采用迷宫式屏蔽结构,作为绝缘体的熔铸云母全部屏蔽在钢制外罩之内,不会因放电而损坏;阴极与底座之间采用可靠的密封方式,长期使用不漏气.实际使用表明,新型离子渗氮炉可大大降低热量损失,增加承重能力,维护保养方便;输电阴极使用三年不用拆卸,工作稳定可靠,劳动生产率比常规的离子渗氮炉提高30%.     

Research on component phases and microstructure shape of a rapid ion nitriding layer

The properties of nitrided parts are closely related to the component phases of their compound layers and microstructure shape of their diffusion layers. Based upon the influence of nitriding temperature and nitrogen (N) potential on formation and decomposition of ion nitriding layer, the component phases and microstructure shape of ion nitrided layer, which was processed under cyclic N potential, was studied with x-ray diffraction (XRD) analysis and transmission electron microscopy (TEM). The mechanism of rapid ion nitriding is also discussed in this paper. The results show that if the rapid ion nitriding by the thermal cycling and the N potential cycling is controlled, the nitriding speed and nitrided layer thickness of materials can not only be enhanced compared to the conventional ion nitriding technique, but also the alloy nitrides can be obviously increased. The precipitation hardness phases of diffusion layer became more trivial and spread in all directions. It is very important to improve the quality of the nitrided layer and to enhance the properties of nitrided parts.     

Intermediate temperature decomposition of supercooled high nitrogen austenite

Abstract

The mechanism of decomposition transformation of Fe–N the austenite system has been investigated. An improved process of austenitic nitriding, achieved by applying controlled nitrogen potential theory, allowed high nitrogen austenite samples with a uniform nitrogen concentration to be produced. The key point of this gas nitriding process is to keep the atmosphere at very low nitrogen potential. As a result, the nitride layer on the surface of the pure iron foil was reduced and pure iron ferrite was thoroughly nitrided, forming high N austenite (γ-Fe[N]) that is thermally stable at room temperature. The nitrogen concentration of this austenite was determined as 9·32 at.-%, which is almost the maximum value achievable in Fe–N austenite.