电压对Q235钢等离子体电解硼碳共渗中光谱特性的影响

采用液相等离子体电解渗方法,在280 V和300 V电压下对Q235低碳钢进行硼碳共渗处理,分析了渗层的显微组织和相成分。研究不同电压下硼碳共渗过程的光发射谱(OES),并评估了等离子体放电区的电子温度、电子浓度特征参数。结果表明,等离子体电解硼碳共渗中放电区的电子浓度大于8×1022m-3,达到局部热平衡状态。电子温度为3000~12000 K,等离子体放电为活性碳原子和硼原子在钢基体中快速扩散创造了高温环境。随着电压的升高,等离子体放电变得剧烈,电子温度明显增加,Q235低碳钢表面岛状硼化物颗粒逐渐增大相连接,形成较厚的渗硼层。     

渗硼工艺研究与应用现状及发展

渗硼能够显著提高金属表面的性能，目前的研究方向主要是降低渗硼温度。多元复合渗硼改善渗层显微组织、显微硬度、脆性和耐磨性，以及渗硼共晶化使渗层与基体呈冶金结合，从而改善以往的渗硼层脆性大、容易剥落等问题。     

等离子电解渗入工艺和渗层组织

介绍了液相等离子体电解渗入技术,即利用液相中的等离子放电实现渗碳、渗氮、渗硼及多元共渗的基本工作原理、工艺特点和电解液成分等。论述了液相等离子体电解渗入过程中的电流-电压特性和物理化学效应。介绍了经液相等离子体电解渗入处理的20CrMnTi和40Cr钢的表面形貌、渗层显微组织和硬度分布。     

电压和占空比对TC4合金表面碳氮共渗层组织与性能影响

在尿素、硝酸铵和蒸馏水组成的电解液体系中,利用液相等离子体电解渗技术在TC4钛合金表面制备碳/氮共渗层,采用SEM、XRD和摩擦磨损试验分析渗层的表面形貌、相结构和磨损性能。试验结果表明:等离子碳氮共渗层主要由TiCN相、TiO相和Ti相组成,工作电压和占空比的提高可以显著增加渗层厚度及硬度,降低渗层的平均磨损率。     

钛合金表面等离子体电解氮碳共渗层的特征与耐蚀性

利用等离子体电解渗技术,在TC4钛合金表面制备了等离子体电解氮碳共渗(PEN/C)层.用X射线和扫描电镜分析了渗层的成分和结构特征;用动电位极化曲线和电化学阻抗谱分析PEN/C渗层在3.5%的NaCl溶液中的电化学腐蚀行为和耐蚀性.结果表明在钛合金表面形成的PEN/C渗层为多孔状Ti(C,N),它提高了基体的腐蚀电位,增大了电荷转移电阻,减小了腐蚀电流密度.PEN/C渗层提高了钛合金基体的耐蚀性.     

20钢固体粉末法渗硼和硼钒共渗的渗层研究

采用光学显微镜、扫描电镜和电子探针等检测手段，分析了20钢固体法渗硼和硼钒共渗的渗层组织结构、成分特点及其硬度分布。结果表明，硼钒共渗层厚度大于单一渗硼层，且渗层更加连续致密，其渗层主要由Fe2B、V2C和VB相组成，硼钒共渗层硬度比单一渗硼有所提高，硬度梯度较小。     

渗硼处理对Cr12冷轧辊表面组织及性能的影响

以Cr12冷作模具钢轧辊为研究对象,通过固体渗硼方法在其表面进行渗硼研究。使用单一变量法研究了渗硼剂类型、渗硼处理温度和处理时间对渗层厚度及性能的影响。同时借助蔡司金相显微镜对渗层组织进行分析,利用环-块摩擦试验机对渗硼前后的试样进行磨损实验。实验结果表明:使用硼铁型渗硼剂得到的渗层较厚,渗层较为平整。在渗硼实验过程中,最佳热处理参数为:渗硼温度950℃,保温时间5 h。在本次实验所选取的热处理参数范围内,渗硼层厚度随温度的升高和保温时间的延长而增加。试样经过渗硼处理后,表面形成的渗硼层增加了表面硬度,提高了表面耐磨性。     

TC4钛合金熔盐电解法渗硼

采用熔盐电解法对TC4钛合金表面渗硼以提高其表面硬度。选用硼砂和碳酸钠的混合盐作电解质,施加1.49 V电压进行渗硼实验,研究熔盐温度对渗层微观形貌及物相的影响,并对熔盐电解渗硼的反应机理进行了探讨。对不同组分的混合熔盐进行示差扫描热量(DSC)-热重(TG)分析,利用X射线衍射(XRD)仪对渗层表面及熔盐进行物相分析,利用扫描电镜(SEM)和能谱(EDS)仪分析渗层断面的形貌和元素成分。结果表明:在900℃时渗硼110 min,可获得均匀密实的渗层,主要物相是TiB_2和TiB;渗硼后试样的表面硬度为7.1 GPa;渗硼后熔盐中的主要产物是NaBO_2;渗层中先有TiB_2相生成,TiB在TiB_2相的下层形成。     

硬质合金渗硼层组织及厚度的研究

本文以WC-Co硬质合金为渗硼研究对象,研究开发出一种感应加热密闭容器气-固渗硼工艺方法 ,借助于金相显微镜对渗硼层厚度实现了直接观察,应用SEM、EDS能谱、XRD、场发射电镜等对合金的组织进行了分析。实验结果表明:渗硼层厚度可达0.1～0.5 mm,渗硼层Co粘结相中弥散分布羽毛状W-C-Co-B析出相;感应加热、密闭容器中气相的作用和渗硼剂中的稀土促进了渗硼过程的进行;硬质合金Co含量、渗硼温度、渗硼时间增加有利于渗硼层厚度增加;应用数据拟合得到了YG11合金渗硼层厚度与渗硼温度、渗硼时间关系表达式。     

中温渗硼应用

介绍了电影机上的导片片零件采用中温硼铝稀土多元共渗工艺,讨论了渗硼过程和渗剂成分、保温时间及淬、回火对渗层的影响。实践证明,中温渗硼零件变形小,成本低,工艺简单,渗硼后零件硬度和耐磨性能满足需要。     

阴极等离子体电解氧化表面改性新方法探索

阴极等离子电解氧化(CPEO)打破等离子体电解领域传统认识,利用液相放电现象,使钢铁及钛基材料阴极表面快速氧化,是一种氧化膜制备新方法,提高了材料的耐磨、耐蚀性能。与微弧氧化或阳极等离子电解氧化技术相比,CPEO技术的氧化膜生长速率显著提高,并适用于各种钢铁材料表面改性。介绍了CPEO技术的基本原理,包括液相放电现象和电压电流的演变过程、气膜形成与击穿过程、阴极内部近表面温度随电压变化规律和快速氧化过程,并对比分析了CPEO与阳极等离子体电解氧化和电解渗技术原理的共性与差异。介绍了光发射谱测量和等离子体参数的计算结果,分析阴极等离子体放电环境中阴极等离子体电解氧化机制。进一步总结了碳钢、不锈钢、Mo、TiAl合金表面CPEO膜的形貌、组织结构和性能特点,分析电解液中悬浮的碳粉特性,探讨放电过程中类金刚石(DLC)成分合成的可行性,并初步制备出含DLC成分的CPEO复合氧化膜。最后总结并展望了CPEO技术的发展方向以及应用前景。     

The Study on Plasma Boriding of H13 Steel at Low Temperature Assisted by Surface Nanocrystallization Technology

Plasma boriding treatment was carried out at low temperature for the hot work die steel H13 assisted by surface nanocrystallization technology in this paper.At the same time,the thermal fatigue property of it was investigated through thermal fatigue testing with 3000 continuous cycles from room temperature to 700℃.The changes of structure and grain size in surface layer were characterized by high-resolution transmission electron microscopy(HRTEM).After plasma boriding at 580℃ for 4 h,the phase composition,morphology and in-situ nanomechanical property of boride layer were investigated by X-ray diffraction spectroscopy(XRD),scanning electron microscope(SEM),nanoindentation test,respectively.The results show that the boride layer with about thickness of 5μm is composed with two phases of Fe2B and FeB.The nanohardness of boride layer is as high as 21 GPa.Furthermore,thermal fatigue testing shows that the boride layer with excellent oxidation resistance and mechanical strength at elevated temperatures could effectively delay the crack initiation and impede the crack propagation.Therefore,the thermal fatigue property of H13 can be remarkably improved.     

纯镁表面等离子体电解渗硼与微弧氧化复合膜的制备及耐蚀性

目的 在纯镁表面制备新型复合膜,以提高其耐蚀性.方法 先在硼砂系电解液中对纯镁进行等离子体电解渗硼(PEB)处理,预制表面改性层,然后在硅酸盐系电解液中对其进行微弧氧化(MAO)处理,从而获得PEB+MAO新型复合膜.分别使用扫描电子显微镜(SEM)、能谱仪(EDS)和X射线衍射仪(XRD)分析膜层的微观结构、元素分布及物相组成,膜层的耐蚀性则通过动电位极化曲线和电化学阻抗谱(EIS)来表征.结果 纯镁的等离子体电解渗硼过程经历了电离、置换、吸附和扩散四个阶段,获得的PEB表面改性层由氧化层和扩散层组成.在PEB+MAO复合膜的生长过程中,膜层在其厚度方向存在重叠的现象,而不是逐层的简单堆积.等离子体电解渗透时,硼元素渗入后所形成的渗层区域降低了纯镁基体表面的化学活性,改善了其微观组织结构,进而使PEB+MAO复合膜的腐蚀电流密度较基体、单一PEB改性层和单一微弧氧化膜层分别降低了3、2、1个数量级.同时,EIS研究也表明,PEB+MAO复合膜可以提供相对较长时间的抗蚀保护.另外,分析了PEB表面改性层的生成机理以及PEB+MAO复合膜的形成过程,并建立了物理模型.结论 PEB预处理会显著影响PEB+MAO复合膜的厚度、致密性及成分,继而明显提高纯镁的耐蚀性.该新型的复合膜制备方法有望进一步推广到镁合金上,以提高其耐蚀性和承载能力.     

Effects of electrochemical boriding process parameters on the formation of titanium borides

In this study, the boriding of titanium via molten salt electrolysis was investigated in borax based electrolyte at various current densities (50–700 mA/cm²), temperatures (900–1200°C) and process durations (1 min-4 h). Thin film XRD results revealed that two main titanium boride phases TiB₂ and TiB was formed even after 1 minute of process time. Scanning electron microscopy (SEM) images conducted on the cross-sections demonstrated a bilayer boride structure composed of a continuous uniform TiB₂ phase and TiB whiskers that grew below the TiB₂ layer toward the substrate. Dependence of boride layer thickness and morphology on the process parameters was evaluated. The results of the study showed that temperature of boriding was the most critical parameter both on boriding rate and morphology of the boride layer. It was possible to grow 8 μm thick TiB₂ layer on titanium in 30 minutes of boriding at 1200°C.     

The effect of boron-pack refreshment on the boriding of mild steel by the spark plasma sintering (SPS) process

Mild steel samples were borided with and without boron pack refreshment using the spark plasma sintering (SPS) process. Results show that the borided samples with boron pack refreshment developed a thicker boride layer compared to that without boron pack refreshment for the same boriding duration. When boriding duration is t < 120 min, the boriding growth in the samples borided with boron pack refreshment followed a parabolic growth pattern. In contrast, the boride growth in samples processed without boron-pack refreshment deviates from parabolic at t = 60 min. Computer simulation shows that the boron concentration change in the boriding media during the boriding process is an important factor affecting the composition and final thickness of the boride layer.     

钛金属表面熔盐电解法制备TiB2/TiB表面层

运用渗硼技术改进金属钛及其合金的表面特性。以无水硼砂为主渗硼剂,无水碳酸钠为助熔剂和高温络合剂的渗剂体系,在电流密度为7.3 A/dm2,保温温度为900℃,通电时间为30 min的电解渗硼工艺下制备出复合硼化物表面层。通过热重与差热图谱确定几种硼砂-碳酸钠配比体系的初晶温度。对4种不同配比的渗硼剂试验得到的样品做XRD测试,分析了相结构。并对硼化物生长机理与结构进行了研究与分析。结果显示:质量比为8∶2的渗硼剂组成最优。纯硼砂电解的样品表面物相组成与二渗硼钛标准粉末的XRD完全吻合。钛金属表面主要生成TiB2与TiB;扫描电镜图像可知渗硼表面致密,TiB2与TiB分层较为明显;TiB厚度可达35μm,TiB2厚度为43μm。     

Characterization of borided pure molybdenum under controlled atmosphere

In this study, the structural characterization and boriding kinetics of the molybdenum borides formed on the surface of borided pure molybdenum (Mo) have been investigated. Boronizing was carried out in solid medium with boron component forming Ekabor ® 2 (90% SiC, 5% KBF₄, 5%B₄C) powders at 1273 K, 1373 K for 2, 4, 6, 8 hours under a controlled atmosphere containing argon gas flow. The boride layer was characterized by the scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), Energy dispersive spectroscopy (EDS) and Vickers microhardness tester. X-ray diffraction analysis showed that the boride layers on molybdenum consisted of MoB and Mo₂B phases. However, the MoB phase was observed at certain boriding temperature and boriding times. The thickness of boronized layers almost ranged from 12 to 42.5 μm with boriding time. A parabolic relationship was observed between boride layer thickness and boriding time. The growth rate constant and activation energy for the boride layer were calculated. The hardness of borides compounds formed on the surface of molybdenum ranged from 925 to 1150 HV_0.05, whereas the hardness of the untreated molybdenum sample was 258 HV_0.05.     

A Kinetic Model for the Boriding Kinetics of AISI D2 Steel During the Diffusion Annealing Process

In this work, a diffusion model was proposed to estimate the boron activation energies for FeB and Fe₂B layers during the pack-boriding of AISI D2 steel at temperatures of 1223, 1253 and 1273 K for a treatment time varying between 2 and 10 h. This model considers the effect of boride incubation times during the formation of the FeB and Fe₂B phases. To study the influence of diffusion annealing process on the boriding kinetics of AISI D2 steel, the mass balance equations were modified in order to follow the evolution of boride layers as a function of annealing time for the specified boriding parameters. Finally, the kinetic model was validated by a comparison of the experimental thicknesses of boride layers with the predicted ones at a temperature of 1243 K for 2, 4 and 6 h. A simple equation was then obtained for estimating the total time necessary to get a single boride layer (Fe₂B) that depends on the boriding parameters and on the thickness of each boride layer prior to the diffusion annealing process.     

Indentation size effect on the Fe2B/substrate interface

This study evaluated the indentation size effect on the Fe₂B/substrate interface using the Berkovich nanoindentation technique. First, the Fe₂B layers were obtained at the surface of AISI 1018 borided steels by the powder-pack boriding method. The treatment was conducted at temperatures of 1193, 1243 and 1273 K for 4, 6 and 8 h at each temperature. The boriding of AISI 1018 steel resulted in the formation of saw-toothed Fe₂B surface layers. The formation of a jagged boride coating interface can be attributed to the enhanced growth at the tips of the coating fingers, due to locally high stress fields and lattice distortions. Thus, the mechanical properties achieved at the tips of the boride layer are of great importance in the behavior of borided steel.Applied loads in the range of 10 to 500 mN were employed to characterize the hardness in the tips of the Fe₂B/substrate interface for the different conditions of the boriding process. The results showed that the measured hardness depended critically on the applied load, which indicated the influence of the indentation size effect (ISE). The load-dependence of the hardness was analyzed with the classical power-law approach and the elastic recovery model. The true hardness in the tips of the Fe₂B/substrate interface was obtained and compared with the boriding parameters. Finally, the nanoindentation technique was used to estimate the state of residual stresses in this critical zone of the Fe₂B/substrate interface.