硬质合金中温钎焊技术的实验研究

采用显微结构法,通过观察钎焊接头形成条件,研究了以B-Ag-1为钎料的硬质合金和钢的中温连接技术。实验表明,在感应电流为450～600 A时,B-Ag-1钎料能湿润并在硬质合金上铺展,形成组织均匀的钎缝,同时通过钎料中银原子和铜原子向硬质合金的扩散形成具有一定强度的界面。钎焊温度的降低以及铜缓冲层的加入,大大降低了钎焊过程的热应力,接头和母材上均未发现热裂纹。     

硬质合金刀具钎焊后性能变化的研究

对硬质合金刀具钎焊前后的硬度、裂纹形成及变化,焊缝质量和切削性能等进行了大量的试验研究。结果表明：硬质合金刀具钎焊后硬度下降范围在HRA1以内;采用延长钎焊后保温时间和增加补偿垫片均可以减少或避免刀具表面裂纹的产生;对18CrMnTi渗碳淬火齿轮（HRC55－58）单齿侧刃铣削中钎焊刀具的切削性能同机夹刀具相比无明显差异,它为硬质合金钎焊刀具在精密切削FMS和其他自动化加工中的广泛应用提供了实验和理论依据。     

45钢与YG6硬质合金的钎焊性能

本文通过对４５钢与ＹＧ６硬质合金的对接钎缝接头金相组织及强度分析，研究了钎焊加热时间、焊后冷却方法等对钎焊接头强度的影响，通过试验确定了一定工艺条件下的最佳钎焊时间及焊后冷却的几个工艺参数。     

硬质合金断裂力学参数的实验研究

对两种国产新牌号硬质合金的断裂力学参数进行了研究。实验表明,表面受控裂纹法可成功地用于评价硬质合金的断裂韧性,压痕处的残余应力可用“裂纹扩展法”加以消除,不会产生副作用;压痕法简单易行,所得结果与表面受控裂纹法相近。双扭试样恒定位移法可用于硬质合金中宏观裂纹亚临界扩展的高速部分,而压痕诱导裂纹法(IIF)可成功地用于微观裂纹亚临界扩展低速部分的特性研究。两部分中的da/dN-△K_1曲线均可用指数函数来描述。     

硬质合金疲劳行为研究

用远场循环压缩方法在淬火硬质合金试件缺口端部引发了自行中止的Ⅰ型疲劳裂纹，在三点弯曲循环载荷下该疲劳裂纹继续扩展，对裂纹扩展的各阶段的断口作了比较和解释。     

硬质合金刀具的脱焊及其控制方法

通过工艺分析及实验研究,揭示了钎料选择不当,钎剂没有进行脱水处理,钎焊工艺选择不当,钎焊法中电压参数不稳定及钎焊过程中刀槽发生了较大的塑性变形是引起硬质金刀具焊的主要原因,进而提出相应的控制措施。     

硬质合金钎焊接头的拘束强化

从力学观点分析了高温高压扩散处理硬质合金钎焊接头的拘束强化效应。文中指出，钎焊接头受力时，钎缝的拘束应力状态与双边半圆缺口平板中的应力状态相类似，据此，在一定范围内建立了钎缝宽度与接头强度间的定量关系，为通过控制钎缝宽度以提高接头强度提供了依据。     

硬质合金气中电火花线切割精加工技术研究

用气体介质代替液体介质，开发出了一种新型的电火花切割精加工工艺．在水、大气、压缩空气和压缩氧气的条件下，进行了硬质合金的气中电火花线切割精加工试验研究．试验结果表明：气中加工时的放电间隙比水加工时小，表面直线度明显优于水中加工，表面粗糙度与水中加工时相近，折断强度值与水中加工的几乎相同．采用水介质加工时，其加工速度(金属去除率)较高．     

Brazing behavior of ultrafine cemented carbide with stainless steel

In order to investigate the effects of brazing temperature, heating rate and cooling methods on shear strength, hardness, magnetic saturation and coercivity of the ultrafine cemented carbide, the ultrafine cemented carbide was fabricated according to conventional powder metallurgical procedures, and then brazed to the stainless steel with silver-based filler alloy by supersonic frequency induction brazing. The microstructure was observed using scanning electron microscope （SEM）, energy dispersive spectroscopy （EDS） and the magnetic properties were tested utilizing coercimeter and cobalt magnetism instrument. The results show that no micro-crack is found in the cemented carbide after brazing because of silver-based sandwich compound used as filler alloy. In the melted silver layer, there is more carbon in the region adjacent to the cemented carbide. Varied shear strengths, hardnesses, magnetic saturations and coercivities are present under different brazing temperatures, heating rates and coolings. This phenomenon is correlated with some factors such as wettability and fluidity of filler alloy, brazing stress, oxidation of cemented carbide, and allotrope transition of cobalt. Shear strength reaches the maximum of 340 MPa and hardness of ultrafine cemented carbide remains 1879 HV at the brazing temperature of 730℃. The carbon increases with the of increase of the heating rate. What＇s more, and there is no r/phase found under this condition. content decreases with the increase of brazing temperature, and it the lowest magnetic saturation reaches 81.8% of the theoretic value,     

WC-Co硬质合金的相组成及其相变

碳化钨（WC）是一种硬度高、热稳定性和耐磨性好的硬质合金材料，WC－Co硬质合金的性能除与WC晶粒的大小有关外，在很大程度上还取决于合金中的相组成及相转变，本文主要依据WC－Co系相图，采用热力学方法对烧结过程中合金的γ,η相的生长条件、成分结构以及相变过程进行了讨论，从本质上阐明WC－Co硬质合金的成相规律和影响因素。     

超重型切削过程硬质合金刀具高温力学特性

超重型切削过程中,刀具的高温失效是硬质合金刀具破损的主要形式之一。首先,通过理论分析、切削仿真及数学模型进行切削热产生过程分析,并研究切削温度对硬质合金刀具变形抗力的影响;然后,进行切削温度及材料高温硬度测量实验,实验结果验证模型有效,硬质合金和工件材料试块的硬度在1000℃时分别下降了28%和60%左右;最后,从刀具几何结构优化设计和复合涂层技术两方面提出超重型切削专用硬质合金刀具抗高温性能的提效措施,在5组切削参数下进行刀具寿命对比实验,优化设计的XF8刀具寿命是YT15刀具的2~5倍。研究结果可以为重型高效切削刀具技术的研究及推广提供借鉴。     

Microstructure and properties of gradient cemented carbide with Nano-TiN

Gradient cemented carbides with nano-TiN were prepared by the common powder metallurgical procedure. The formation of gradient zone and the microstructure, properties of the alloys were investigated using scanning electron microscope（SEM）, energy dispersive spectroscopy（EDS） and other performance testing apparatus. Moreover, the effect of nano-TiN on the gradient cemented carbide was studied. It is found that gradient zone width increases slightly with nano-TiN introduction. Both cobalt and titanium concentrations reach the maximum near the gradient border. Tungsten concentration shows fluctuation from the surface to the bulk. （Ti ,W）C phase grains are refined for nitrogen introduction. Core-rim structure has been observed under the SEM back-scattered mode. The core appears as dark due to more titanium in it and the rim with more tungsten appears as grey. In addition, the hardness and transverse rupture strength of gradient cemented carbide are enhanced with nano-TiN introduced.     

硼浓度对沉积在刀具上的金刚石膜表面的影响

在热丝CVD装置中，以氢气、丙酮、硼酸三甲脂为原料，在YG6上制备了含硼金刚石薄膜．研究丙酮中硼含量对薄膜表面晶形及晶粒度的影响．结果表明，薄膜中渗入适量的硼不改变薄膜表面晶形，细化晶粒．有利于薄膜附着力的提高；而过高的硼含量恶化金刚石薄膜质量，降低薄膜附着力．     

Rare earth doped new cemented carbide with Ni-Co binder for mining

ＴｈｅｗｅａｒｒｅｓｉｓｔａｎｃｅｏｆｔｈｅｔｒａｄｉｔｉｏｎａｌＷＣ Ｃｏｃｅ ｍｅｎｔｅｄｃａｒｂｉｄｅｆｏｒｍｉｎｉｎｇ ,ｗｉｔｈｔｈｅａｄｄｉｔｉｏｎｏｆｒａｒｅｅａｒｔｈ ,ｃａｎｂｅｉｍｐｒｏｖｅｄｏｂｖｉｏｕｓｌｙ[1] .Ｂａｓｅｄｏｎｔｈｅｉｎ ｈｅｒｅｎｔｓｉｍｉｌａｒｉｔｙｂｅｔｗｅｅｎＷＣ ＣｏａｎｄＷＣ Ｃｏ Ｎｉｃｅｍｅｎ ｔｅｄｃａｒｂｉｄｅｓｉｎｔｅｒｍｓｏｆｍｉｃｒｏｓｔｒｕｃｔｕｒｅ ,ｗｅｃａｒｒｉｅｄｏｕｔｔｈｅｓｔｕｄｙｏｆＷＣ Ｃｏ Ｎｉｃｅｍｅｎｔｅｄｃａｒｂｉｄｅｗ…     

Mierostrueture and Properties of Coating from Cemented Carbide on Surface of H13 Steel

The microstructures and properties of coating from cemented carbide on the substrate of H 13 by vacuum powder sintering were studied. The effect of sintering temperature on the microstructures of coating was discussed. The interface characteristics between coating and H 13 steel substrate, microhardness distribution and wear resistance in the coating were analyzed. The coating from cemented carbide with thickness of 1-3 mm by vacuum powder sintering at temperature ranging from 1280℃to 1300 ℃ was obtained. The experimental results indicated that the coating with microhardness of HV 1600 favorable to wear resistance is strongly bonded with the H 13 steel substrate by mutual diffusion and penetration of Fe,Cr, Mo,V in substrate towards the coating and W, Co,Ni in coating towards the substrate.     

Abnormal gradient microstructure in Cr_3C_2 based cemented carbide

Ｃｒ3 Ｃ2 ｂａｓｅｄｃｅｍｅｎｔｅｄｃａｒｂｉｄｅｓａｒｅｃａｌｌｅｄｔｈｅ“ｓｔａｉｎｌｅｓｓｓｔｅｅｌ”ａｍｏｎｇｃｅｍｅｎｔｅｄｃａｒｂｉｄｅｓｆｏｒｔｈｅｉｒｕｎｉｑｕｅｐｒｏｐｅｒｔｉｅｓ ,ｓｕｃｈａｓｅｘｃｅｌｌｅｎｔｃｏｒｒｏ ｓｉｏｎｒｅｓｉｓｔａｎｃｅｉｎｖａｒｉｏｕｓａｃｉｄｓ,ｏｘｉｄａｔｉｏｎｒｅｓｉｓ ｔａｎｃｅａｔｈｉｇｈｔｅｍｐｅｒａｔｕｒｅａｎｄｃｏｍｐａｒａｂｌｅ ｔｏ ｓｔｅｅｌｔｈｅｒｍａｌｅｘｐａｎｓｉｏｎｃｏｅｆｆｉｃｉｅｎｔ,ｓｕｇｇｅｓｔｉｎｇａｇｏｏｄｗ…     

Directional migration behavior of cerium during sintering process of mischmetal doped cemented carbide

Three observation methods were used to investigate the existing form and the behavior of rare earth during the sintering process of high activity mischmetal （RE, with lanthanum and cerium） doped WC-8%Co-0.048%RE（mass fraction） alloy with low carbon-containing level by scanning electron microscopy （SEM） and energy dispersive X-ray spectroscopy （EDXS）, considering the fact that the addition amount of rare earth in the alloy is very minute. The directional migration process and mechanism of cerium were discussed. First, the sinter skin （surface） is observed. oxide on the sinter skin, and lanthanum in these cerium observed, and lanthanum containing phase/micro-zone in It is shown that there exists a dispersedly distributed cerium containing enrichment positions is very minute. Secondly, the polished section is the alloy is identified. Finally, based on the fact that the fracture of cemented carbide is resulted from the heterogeneous phase or other defects within the microstructure, the fracture surface is observed and cerium containing phase/micro-zone in the fracture source approximately 260 μm from the surface is identified. These combined observations reveal adequately the fact that lanthanum and cerium get separated and cerium predominantly migrates towards the surface during the sintering process.