Surface hardening of Fe-based alloy powders by Nd:YAG laser cladding followed by electrospark deposition with WC-Co cemented carbide

This paper presents the results of a study concerned with the surface hardening of Fe-based alloys and WC-8Co cemented carbide by inte- grating laser cladding and the electrospark deposition processes. Specimens of low carbon steel were processed firstly by laser cladding with Fe-based alloy powders and then by electrospark deposition with WC-SCo cemented carbide. It is shown that, for these two treatments, the electrospark coating possesses finer microstructure than the laser coating, and the thickness and surface hardness of the electrospark coating can be substantially increased.

Interface behavior study of WC92-Co8 coating produced by electrospark deposition

ESD (electrospark deposition) is a promising process to produce hard and wear-resisting coatings on metallic substrates. In this paper microstructure and interfacial characteristics of the WC92-Co8 coated on titanium and carbon steel are presented. A metallurgical bonding between the coating and substrate is obtained. The Ti element was found to distribute in WC92-Co8 at the metal pool, as well as the interface by diffusion. Some new phases were produced in the coating layer due to the chemical reaction during the ESD process. Experimental observation and thermodynamic analysis were utilized to study the mechanism of ESD.

Effect of Electrospark Alloying Process on Microstructure and Properties of the coating

Using electrospark alloying machine, a series of experiments were carried out to investigate the effect of electrospark surface strengthening process on the microstructure and the properties of the coatings with ultrafine cemented carbide as electrode material and white cast iron as substrate material. The results indicated that the optimum process parameters to be used reached a satisfying coating surface. Wear test results showed the coatings had a high wear-resistance.

Influence of Carbon Content of WC-Co Electrode Materials on the Wear Resistance of Electrospark Coatings

In the electrospark deposition (ESD) of WC-Co materials on low carbon steel, tungsten carbide (WC) decarburization is observed. The use of an inert atmosphere (argon) does not eliminate the problem of tungsten carbide decarburization during electrospark processing. The effect of the carbon concentration of electrode materials on the phase composition and mechanical properties of WC (10 wt% of Co) ESD coatings has been investigated in this work. The introduction of additional carbon (graphite) in the electrode material on the basis of the WC-10%Co leads to an increased amount of WC in the obtained coatings and thus improves their wear resistance.

Electrospark Coatings Based on WC-Co Alloys with Aluminium Oxide and Carbon Additives

The structure and properties of coatings based on WC-Co alloys containing additives of 1% - 5% aluminium oxide and 2.5% - 4.5% carbon were investigated. The coatings had a nanocrystalline structure. Depending on the duration and frequency of the discharge pulses, the ratio between WC and W2C in the coatings was different. The additives in the hard alloy allowed us increase the microhardness and wear resistance of the coatings by a factor of 2 - 3 in comparison to coatings created using a conventional WC-10%Co alloy.

Research on depositing Ni45 alloy on titanium alloy surface by electrospark deposition

Taking Ni45 bar as electrode,a strengthened layer of thickness up to 50μm was built up on BT20 titanium alloy matrix by means of electrospark deposition.Results of phase analysis by using of X-ray diffraction confirmed that the deposition layer was composed mostly of three phases,NiTi,NiTi2 and Ti.The surface microhardness of the deposition layer was up to 910 HV0.05,about 2.7 times as high as that of the matrix.The hardness at the cross-section of the entire deposition layer showed a gradient distribution.The effects of capacitance and deposition time on thickness of deposition layer were also studied,and results showed that with relatively low capacity and short deposition time the deposition layer without cracks can be obtained.

M CrAlY/TaC Metal Matrix Composite Coatings Produced by Electrospark Deposition

MCrAlY/TaC metal matrix composite coatings with 10, 20 and 30 wt.% TaC have been successfully produced by electrospark deposition （ESD）. The effects of TaC content on microstructure, hardness and oxidation behavior of the composite coatings were studied. The results showed that the composite coatings were composed of superfine 9＇ columnar dendrite and large TaC particles dispersedly distributed. The hardness was enhanced but oxidation resistance of the composite coatings was reduced with increasing TaC contents.

Preparation and mechanical properties of two nickel base alloy coatings achieved by electrospark deposition

Ni398 and Ni818 base alloy coatings were deposited on 1045 steel by electrospark deposition technique （ESD）. Forming properties, thickness, microhardness and wear resistance of the coatings were investigated. The chemical composition and cross- section morphology were analyzed through energy dispersive spectrum （EDS） and metalloscope. The results show that the technological parameter window of Ni398 is larger than that of Ni818 electrode. However, other properties of the Ni818 coating, such as thickness and microhardness, were better than those of the Ni398 coating. Especially the wornout volume of Ni818 coating is only 1/6 of that for 1045 steel and 1/3 for Ni398 coating. Chemical composition analysis indicated that the addition of Mo promoted grain refinement of nickel alloy. Metallographic analysis shows that the molten droplets of Ni398 coatings have an average structure thickness of 20-40 #m while the microstructure of Ni818 coatings is flat with width of 5-20 #m.

钢表面电火花沉积合成W-Mo高熔点复合涂层

目的 采用ZY-10型电火花堆焊/涂层沉积设备,分别以钼和钨棒料为电极,以超纯氩气为保护气体,在PCrNi3MoVA钢基体表面沉积合成W-Mo高熔点复合涂层。方法 在PCrNi3MoVA钢基体表面先沉积出一定厚度的钼涂层作为打底层,在此基础上,采用更高的电参数沉积硬度和熔点都较高的钨涂层。作为同族元素的钼和钨,在高温电弧作用下能较好地合成W-Mo高熔点复合涂层。通过对复合涂层的成分、微观形貌等进行观察和分析,用等离子烧蚀实验检测复合涂层的抗烧蚀性能,并计算复合涂层的质量烧蚀率和线烧蚀率。结果 采用电火花沉积工艺在PCrNi3MoVA钢基体表面成功制备了W-Mo高熔点复合涂层,其厚度达到100μm以上,该复合涂层主要由W、Mo、Fe等成分组成,且越靠近涂层表面,W和Mo元素的含量越高,复合涂层主要有Mo、MoC、Fe_(2)Mo_(3)、Fe_(2)W等物相,复合涂层的耐烧蚀性能较好,在前10 s内其线烧蚀率仅为0.090~0.267 mm/s。结论 W-Mo高熔点复合涂层的厚度随着沉积次数和沉积电压的增加而增加;复合涂层与基体相互熔融,具有较好的冶金结合特征;复合涂层能够承受等离子火焰的短时高温冲击与冲刷,增加复合涂层的厚度可以有效抑制涂层试样烧蚀率的增加。

Q235钢表面电火花沉积铁基非晶改性层及其性能

采用电火花沉积技术在Q235钢表面制备了Fe基改性层,以提高Q235钢的硬度、耐磨性和抗高温氧化性。通过X射线衍射(XRD)、扫描电镜(SEM)、能谱仪(EDS)和高温循环氧化试验对比了基体和改性层的微观结构及抗高温氧化性能。结果表明,所得改性层为非晶态结构,在700℃退火6 h能实现晶化转变;改性层厚度约为12.5μm,表面呈现丘陵状形貌,与基体之间存在很好的冶金结合;电极成分中的Al、Cu和Sn分布于改性层整个表面,并且在凸起和凹陷处的含量更高;相对于基体,改性层具有更好的抗高温氧化性能。改性层的显微硬度为265.90 HV,高于基体和晶化转变改性层,耐磨性也更优。

电火花沉积工艺参数对涂层质量影响的研究现状

电火花沉积作为一种比较成熟的表面处理技术,输入热量小,对基材的热冲击和变形小,涂层与基材为冶金结合,广泛应用于零件表面改性和失效零件表面的修复。本文介绍了电火花沉积技术的原理,总结了近年来国内外电火花沉积技术的主要工艺参数(脉冲能量、比沉积时间、电极尺寸、沉积接触力和沉积气氛)对涂层质量、沉积效率、涂层硬度、厚度的影响规律。近年来,电火花沉积技术与其他技术相结合,可进一步提高涂层质量,通过双电极沉积方式的运用和设计,可得到复合涂层和复相涂层,扩大涂层应用范围。

转向架关键部件低热输入增材修复工艺研究

为优选转向架金属部件局部增材修复用的补焊工艺,文章将电火花沉积、火焰钎焊和脉冲冷焊3种低热输入焊接工艺用于40Cr钢的局部焊补,通过微观组织观察、硬度分布测试、弯曲和剪切性能测试评估补焊层的结合强度,并通过焊后工件的变形量和热影响区拉伸性能评判补焊工艺对工件的整体影响程度。结果表明:电火花沉积工艺的连接强度难以满足转向架部件的使用要求,不适用于转向架部件的局部缺陷修复;火焰钎焊以黄铜焊丝作为钎料时,连接界面存在脆性的Fe-Si界面反应层,致使连接强度降低。此外,火焰钎焊虽然加热温度低,但加热时间长,形成较宽的热影响区,不仅试件变形较大,而且热影响区的抗拉强度比母材下降20%,也不适用于转向架关键部件进行局部增材修复。脉冲冷焊工艺具有结合强度高、热影响区窄、对母材性能影响小及焊后工件变形小等优点,并且所需焊材方便生产现场就地取材,工艺过程简单,是3种备选工艺中最适合于对转向架关键金属部件进行局部增材修复的工艺方法。

电火花表面强化层组织结构和性能的研究

采用电火花表面强化设备,以DH-1型硬质材料作为强化电极材料,白口铸铁为基体材料,研究了电火花表面强化工艺对强化层性能的影响.结果表明,选择合适的工艺参数,可获得较好的强化层表面质量,且强化层硬度高,耐磨性显著提高.

钛合金表面电火花沉积WC涂层的研究

以WC为电极 ,采用不同的电火花强化工艺 ,在钛合金表面制备了强化涂层。为了比较不同工艺条件下获得涂层的组织结构 ,确定最佳的电火花沉积工艺 ,通过金相、SEM、EDS等试验方法对涂层的微观组织结构进行了研究。结果表明 ,仅改变电火花沉积参数对获得性能优良的沉积涂层效果不明显 ,当复合超声加工 ,并且达到一定频率范围时 ,可以明显改善涂层质量。所获涂层是由基体中Ti元素与WC电极发生反应生成的反应涂层 ,涂层的主要成分是TiC、W和W2 C。

电火花表面强化技术的研究进展

介绍了电火花表面强化的原理与特点,概述了电火花表面强化技术的研究现状,指出了电火花表面强化技术的发展趋势。

电火花沉积表面处理技术的应用进展

电火花沉积是一种具有独特技术优势,节能、省材、环保的新兴材料表面处理技术,不仅广泛应用于工具、模具、刃具、矿山、冶金、汽车、医用器材等一般工业领域,还可以应用到核反应堆、直升机和战机引擎等军工零部件的表面处理。介绍了电火花沉积技术的特点,通过典型事例介绍了该技术在耐磨损、耐腐蚀、抗氧化、表面修复与改性方面的应用,分析了电火花沉积技术的应用现状,指出了国内在电火花应用和研究方面与国外的差距,并提出了促进我国表面技术研究者积极研究并大力推广应用的建议。

电火花涂层的特性和耐磨性研究

采用电火花表面强化设备,以YS2硬质合金作为强化电极在45钢表面涂覆形成一层合金强化涂层。用扫描电镜、X射线衍射仪和显微硬度计分析了电火花表面强化层形貌、性能和组织结构。在磨损试验机上对其耐磨性进行测试,同时利用扫描电镜对试样的磨损形貌进行观察分析。结果表明,获得了冶金结合的强化层,显著提高了基体的硬度和耐磨性。

氮气流量对TC11钛合金表面电火花原位反应沉积TiN强化层显微组织和摩擦学性能的影响（英文）

为提高钛合金表面耐磨性能,运用电火花沉积技术在TC11钛合金表面原位反应沉积TiN强化层,研究N2流量对强化层显微组织和摩擦学性能的影响。结果表明：当N2流量过小时,强化层厚度较薄,主要由Ti2N、α-Ti、TiO和TiN等相组成,电火花快速放电导致基体表面产生的熔池急速冷凝,使得亚稳态Ti2N相保留在强化层中;当N2流量过大时,强化层微裂纹和孔洞等缺陷较多;而当N2流量适中时,强化层主要由TiN等物相组成,且致密均匀（50~55μm）,平均显微硬度达HV0.21165.2,是TC11钛合金基体的3.4倍。当N2流量适中时,TiN强化层的耐磨性能最好,此时其磨损质量为0.4 mg,是TC11基体的2/9,其主要磨损机理为微观切削磨损和多次塑变磨损。

TC1合金表面电火花沉积WC-8Co涂层界面行为

钛合金在航空、航天工业得到了广泛应用。但其耐磨性差,对磨面容易产生粘结及对微动磨损敏感等缺点,限制其应用领域的进一步扩大。实践证明,采用电火花强化技术在TC1合金表面制造WC-8Co强化层,可以有效提高TC1基体表面耐磨性能。作者研究了WC-8Co强化层的表面状态、界面行为以及相结构组成,认为TC1合金表面强化高熔点的WC-8Co材料,厚度可大于50μm;强化层与基体之间存在过渡区;强化层表面由TiC、W_2C和少量W组成;强化层截面的显微硬度是基体的3倍以上。