Quantitative Analysis on Carbon Migration in Double-Glow Discharge Plasma Surface Alloying Process

Carbon migration is of great significance in double-glow discharge plasma surface alloying process, but literature of quantitative analysis about carbon migration is relatively scarce. In this paper differential equations of the carbon and metal concentration distribution were established. By means of differential equations carbon migration was described and a numerical solution was acquired. The computational results fit the experiment results quite well.

Surface alloying of Cu with Ti by double glow discharge process

The surface of pure copper alloyed with Ti using double glow discharge process was investigated. The morphology, structure and forming mechanism of the Cu-Ti alloying layer were analyzed. The microhardness and wear resistance of the Cu-Ti alloying layer were measured, and compared with those of pure copper. The results indicate that the surface of copper activated by Ar and Ti ions bombardment is favorable to absorption and diffusion of Ti element. In current experimental temperature, as the Ti content increases, the liquid phase occurs between the deposited layer and diffused layer, which makes the Ti ions and atoms easy to dissolve and the thickness of Cu-Ti alloying layer increase rapidly. After cooling, the structure of the alloying layer is composed of CuTi, Cu4Ti and （Cu（Ti）） solid solution. The solid solution strengthening and precipitation strengthening effects of Ti result in high surface hardness and wear resistance.

Study on Mo Diffusion in Double Glow Plasma Surface Molybdenizing of Ti_2AlNb

Ti2AlNb orthorhombic alloy is an attractive high temperature structural material for aero-industries due to its high specific strength and fracture toughness as well as excellent creep resistance. However, insufficient wear-resistance is the main drawback which restricts the actual uses of this alloy in many circumstances. A double glow plasma surface molybdenizing on Ti2AlNb alloy is carried out as an attempt to resolve this problem. This paper deals with the effects of key process parameters on the diffusion behavior of Mo. The composition distribution and microstructare of the alloying layer are analyzed by SEM, XRD and GDS. Micro-hardness distribution profile is measured along the distance from surface to center. The results indicate that both the temperature and the processing time have significant effects on the diffusion process. Finally, the dif- fusion coefficient at optimized temperature of 980℃ is calculated through regression analysis.

Double Glow Plasma Surface Alloyed Burn-resistant Titanium Alloy

Conventional titanium alloy may be ignited and burnt under high temperature, high pressure and high gas flow velocity condition. In order to avoid this problem, we have developed a new kind of burn-resistant titanium alloy—double glow plasma surface alloying burn-resistant titanium alloy. Alloying element Cr , Mo, Cu are induced into the TJ-6A1-4V and Ti-6.5Al-0.3Mo-l.5Zr-0.25Si substrates according to double glow discharge phenomenon, Ti-Cr ,Ti-Mo, Ti-Cu binary burn-resistant alloy layers are formed on the surface of Ti-6Al-4V and Ti-6.5Al-0.3Mo-l.5Zr-0.25Si alloys. The depth of the surface burn-resistant alloy layer can reach to above 200 microns and alloying element concentration can reach 90%. Burn-resistant property experiments reveal that if Cr concentration reach to 14%, Cu concentration reach to 12%, Mo concentration reach to 10% in the alloying layers, ignition and burn of titanium alloy can be effectively avoided.

A Study of Multi-Permeating TiN/Ti Alloying Layer Using Plasma Surface Alloying Technology

TiN/Ti multi-permeating alloying layer has been formed on the low carbon steel by means of the double glow-discharge plasma surface alloying technique and hollow-cathode effect. The alloying layer was detected by axiovert 25 CA optical microscope with computer analyzing software （LEC）, GDA-2 glow discharge spectroscopy （GDS）, X-ray diffraction （XRD） and galvanochemical method. The results showed that the thickness of TiN/Ti multi-permeating alloying layer was about 10μm, the content of Ti on the surface was up to 63.48 wt% and the content of N was up to 12.46 wt%. The atom Ti and N concentrations changed gradually across the depth of the alloying layer and the preferred orientation of TiN/Ti alloying layer was crystal surface （200）. The multi-permeating alloying layer and substrate were combined through metallurgy. The surface appearances of the multi-permeating alloying layer were uniform and of a compact cellular structure. The hardness of the surface was about 1600-3000 HV0.1. The corrosion resistance of the permeating TiN/Ti alloying layer in 0.5 mol/L H2SO4 solution was greatly increased and the corrosion rate was only 0.3082 g/m^2. h.

Plasma surface alloying of titanium alloy for enhancing burn-resistant property

Conventional titanium alloy may be ignited and burnt under high temperature, high pressure and high gas flow velocity condition. In order to avoid this problem,burn-resistant alloying layers were made on the surface of Ti-6Al-4V and Ti-6.5Al-0.3Mo-1.5Zr-0.25Si titanium alloys by using double glow plasma surface alloying technology (DG Technology). Two typical burn-resistant layers Ti-Cr and Ti-Mo were made by DG plasma chromizing and DG plasma molybdenizing, respectively. Burn-resistant properties were tested by layer ignition method using 2 kW laser machine. Ignition experiments result reveals that the ignition temperature of alloyed layer with Mo and Cr concentration above 10% is about 200℃higher than ignition temperature of Ti-6Al-4V substrate.

工业纯铁表面离子W、Mo、Co多元共渗扩散行为

采用双层辉光离子渗金属技术在工业纯铁表面进行W、Mo、Co多元共渗,分别采用0.5、1、2和3h等渗金属时间,研究了合金层中W、Mo、Co含量随渗金属时间的变化规律。研究表明:渗金属初期,合金层中W含量>Co含量>Mo含量;渗金属后期,合金层中Co含量>W含量>Mo含量。理论分析认为:在渗金属初期,W、Mo、Co扩散主要受各元素原子与空位交换难易程度以及基体表面各元素活性原子量的控制;在渗金属后期,W、Mo、Co扩散主要受各元素在基体中的溶解度的控制。

Fe-Co-W-Mo型表面时效硬化合金的表面时效硬化特性(Ⅱ)

利用双层辉光离子渗金属技术在工业纯铁表面形成高钴的Fe Co W Mo型表面时效硬化合金。研究表明 ,这种表面合金具有时效硬化迅速、硬化能力强和抗回火软化能力强的特点。合金经 1 2 4 0℃固溶处理后于 540℃时效 5min ,硬度就从固溶态的 50 0HV0 .2 左右上升到 750HV0 .2 ;时效 40min ,硬度上升到 1 2 0 0HV0 .2 左右 ;于70 0℃回火 2h ,表层硬度仍保持 72 0HV0 .2 以上。

Fe-W-Mo-Co多元渗镀复合层研究

采用双层辉光离子渗金属技术,在工业纯铁和20钢表面进行W、Mo、Co多元共渗,形成Fe W Mo Co型渗镀复合层.对渗镀层进行了金相组织观察、成分及硬度测量,重点研究了镀层的相组成及镀层与基体间的结合强度.结果表明:纯铁和20钢表面镀层以金属钨、钼为基体,其上分布大量μ相,并有少量Laves相;镀层硬度高达1000～1400HV,固溶和时效处理对硬度提高影响不大;纯铁表面镀层在渗金属、固溶、时效状态下,持续加载100N未发生镀层剥落现象;20钢表面镀层经固溶处理后,所加载荷在100N内未发生剥落现象,但在渗金属及时效态,当载荷加至80N时,镀层开始剥落.

Corrosion property of copperized layer on Zr formed by double glow plasma surface alloying technique

Zr and its alloys have excellent mechanical properties as new structural material,but in specific application environment,its corrosion resistance still needs to be further explored.In this work,double glow plasma surface alloying technique was used for copperizing on pure Zr surface.Besides,X-ray diffraction（XRD）,scanning electron microscope（SEM） and energy dispersion spectrum（EDS） were employed to characterize the samples.Furthermore,research was also conducted on the polarization curve of the samples in different solutions.Copperizing on surface can improve corrosion resistance of pure Zr in 3.5 % Na Cl and 0.5 moláL-1Na OH solutions.Especially in 0.5 moláL-1Na OH solution,the corrosion resistance can achieve significant improvement.However,copperizing has no influence on the improvement of corrosion resistance of pure Zr in 0.5 moláL-1H2SO4 solution.The results may provide new insight into way for improving the corrosion property of zirconium alloys.

W Mo Co多元共渗扩散交互作用规律研究

采用双层辉光离子渗金属技术分别对工业纯铁进行了单元渗W、W-Mo二元共渗、W-Mo-Co三元共渗。通过相同渗金属工艺条件下合金层厚度对比,利用扩散热力学、扩散微观理论以及渗入原子的空位占有率等理论,揭示了渗金属条件下W、Mo、Co三种合金元素的扩散交互作用规律。分析结果表明,多元共渗过程中,共渗元素之间会对彼此的化学势、元素的空位浓度、元素的空位占有率等产生影响,进而影响到元素的扩散速率。

T8钢表面W-Mo-Co多元共渗层的组织和性能

采用双层辉光离子渗金属技术在T8钢表面进行了W—Mo—Co多元共渗，研究了表面合金层的组织、相组成、成分、硬度、脆性以及与基体的结合强度。结果表明，舍金层由MeC＋MC型碳化物层和W、Mo、Co固溶体扩散层组成。碳化物层硬度很高，渗金属态HV0.025硬度高达1200～1400，固溶、时效处理后硬度升高至1400～1600左右；固溶体扩散层在渗金属态硬度较低，HV0.025硬度只有400～550，固溶、时效处理后硬度升高至800～1000。碳化物层与基体之间为冶金结合，不存在膜基结合问题。

双辉离子W、Mo、Ti三元共渗特性研究

采用双层辉光离子渗金属技术 ,对工业纯铁、2 0钢、4 5钢和T8钢进行了W、Mo、Ti离子三元共渗 ,着重探讨了Ti的渗入特性。结果表明 ,渗层成分、组织因工艺条件不同而异 ,典型组织为合金沉积层、合金铁素体和合金珠光体。在同样工艺条件下钛元素不易渗入 ,在渗层中浓度较低 ,但通过工艺参数和源极成分的合理调整 ,可获得约 2 %Ti,W、Mo浓度与高速钢类似的合金铁素体层 ,为含钛表面冶金高速钢的制备提供了必要条件。

双层辉光离子渗W-Mo后球状析出相的研究

在双层辉光离子渗钨钼后形成了多种形态的析出物 ,本文主要针对其中的球状相 ,首先利用 SEM对球状相进行了微区成分分析 ,同时给出了它与 μ相析出的关系图 ;其次主要讨论了球状相的分布特点以及形成原因。对于球状相形成原因的探讨 ,有利于进一步澄清双层辉光离子渗钨钼后试样产生脆性的原因 。

Ti-6Al-4V钛合金的等离子W-Mo共渗

采用双层辉光等离子表面合金化技术对Ti-6Al—4V钛合金进行W—Mo共渗，研究了880—1000℃ W-Mo共渗时基体温度对渗层厚度的影响，采用SEM和XRD观察、检测渗层组织结构和相组成。结果显示，Ti-6Al—4V合金的W-Mo渗层组织良好。纳米压痕试验结果表明，合金渗层硬度高于基体。

双层辉光离子渗W-Mo后析出物TTT图测定

双层辉光离子渗W Mo后由于冷却速度缓慢 ,渗层中尤其在晶界上出现大量析出物 ,造成渗层质量严重下降 ,虽后经固溶处理 ,但由于其组织遗传等原因 ,依然造成不良影响。针对这个问题 ,首先采用恒电流电解萃取析出物 ,然后用X射线衍射法对析出物进行定性分析 ,结果表明析出物主要为 μ相 ;其次应用金相法和定量金相分析仪测定了析出相的等温转变动力学图 ,该图表明析出相分别在 950℃和 1 1 50℃达到转变高峰 ,孕育期分别为 6～ 8min和 4～ 5min。

表面等离子W-Mo合金化对粉末冶金齿轮组织成分及耐磨性能的影响

目的通过表面等离子W-Mo合金化提高粉末冶金齿轮硬度与耐磨性能。方法采用双层辉光等离子表面冶金技术,在粉末冶金齿轮表层制备W-Mo合金层。通过扫描电镜和能谱仪分析合金层的表面形貌和化学成分,用显微维氏硬度仪测量基体与合金层的显微硬度,通过不同载荷下往复式摩擦磨损实验研究等离子W-Mo合金化对粉末冶金齿轮耐磨性能的影响。结果通过双辉等离子冶金技术在粉末冶金齿轮表面成功制备了W-Mo合金层,合金层与基体为冶金结合。经双辉等离子表面W-Mo合金化后的基体的平均显微硬度由之前的145.8HV0.1提升至344.4HV0.1,提升了约1.4倍。不同载荷下的摩擦磨损实验结果表明,经W-Mo合金化后,试样摩擦系数由0.6~0.7降至0.45~0.5左右,下降了约30%。随着载荷的增加,基体与合金层的磨损体积增加,比磨损率由基体的18.70×10^-5~36.16×10^-5mm^3/(N·m)降至合金层的2.99×10^-5~8.79×10^-5mm^3/(N·m),约下降74%~84%。基体存在磨料磨损和粘着磨损现象,而W-Mo合金层则表现出轻微的磨料磨损。结论 W-Mo合金层显著提升了粉末冶金齿轮的硬度和耐磨性。表面等离子W-Mo合金化为粉末冶金齿轮的表面强化工艺提供了新的技术思路。

双层辉光离子W-Mo共渗层中的溶质贫化现象研究

论述了双层辉光离子钨钼共渗层中的沿晶界贫化、表面贫化和晶内析出物μ相周围的贫化现象.分析了贫化的形成原因及其对工件性能的影响,提出了消除贫化现象的方法.

γ-TiAl表面双辉等离子W-Mo合金化对其氧化行为的影响

目的研究W-Mo表面合金化对γ-TiAl合金抗高温氧化性能的影响。方法采用双层辉光等离子合金化技术在γ-TiAl合金表面进行W-Mo合金化,通过恒温氧化试验评价改性层的抗氧化性能,并通过扫描电子显微镜与X射线衍射仪对氧化膜表面及截面形貌和相组成进行分析。结果使用双层辉光等离子合金化技术可以在γ-TiAl表面制备出W-Mo改性层,改性层厚度为9μm,最外层为厚约6μm的W-Mo沉积层,而在沉积层与基体之间存在厚约3μm的扩散层。W-Mo改性层均匀、致密,基体与改性层之间没有裂纹、孔洞等明显缺陷,扩散层中的元素含量呈梯度分布。在750℃恒温氧化100 h后,γ-TiAl基体的氧化增重为5.306 mg/cm^2,W-Mo改性层的氧化增重为2.578 mg/cm^2,仅为γ-TiAl基体的48.6%。在氧化10、20、50 h后,改性层表面无明显变化,氧化膜层均匀、致密、无缺陷,几乎没有出现剥落现象;氧化100 h后,改性层中Mo与W的原子比由3:1降低到了1:2。结论通过双层辉光等离子合金化技术制备W-Mo改性层,能够改善γ-TiAl合金在750℃下的抗高温氧化性能。W-Mo改性层在经过氧化后所形成的氧化膜连续、致密,可以阻碍氧原子向基体内的扩散。但在氧化100 h后,Mo元素的蒸发会破坏氧化膜的完整性,使抗氧化性能有所降低。

纯铜表面Ta-W合金层的抗高温氧化及摩擦行为

采用双辉等离子渗金属技术在纯铜表面通过添加过渡层金属钽制备Ta-W合金层,通过在400℃下恒温氧化试验对比分析铜基体与Ta-W合金层的氧化性能,利用纳米压入和摩擦磨损试验评价Ta-W合金层的硬度和高温耐磨性能。结果表明,Ta-W合金层以胞状结构为主,均匀致密,厚度约为13μm,各层间元素含量呈梯度分布,界面结合良好,表面为单一的α-W相。在400℃恒温氧化50 h后,纯铜基体的氧化增重为13.9 mg/cm^(2),Ta-W合金层的氧化增重为4.6 mg/cm^(2),仅为纯铜基体的33.1%。Ta-W合金氧化试验后形成的氧化膜由WO和WO组成,连续致密、无缺陷,完整地覆盖住基体,有效阻碍了氧原子渗入基体,显著改善了纯铜基体的抗氧化性能。与纯铜基体相比,Ta-W合金层的表面纳米硬度从1.07 GPa提高到11.99 GPa,硬度显著提升;Ta-W合金层的平均摩擦系数变化不大,但摩擦系数的波动幅度显著降低,比磨损率由基体的13.77×10mm^(3)/(N·m)降至Ta-W合金层的7.24×10mm^(3)/(N·m),耐磨性得到提高,纯铜基体的磨损机制主要是粘着磨损、氧化磨损和磨粒磨损的共同作用,而Ta-W合金层则表现出轻微的磨粒磨损。