Form and Distribution Characterization of Reaction Products at the Brazing Interface Between Ni-Cr Alloy and Diamond
Form and Distribution Characterization of Reaction Products at the Brazing Interface Between Ni-Cr Alloy and Diamond
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DOI：
10.4028/www.scientific.net/kem.259-260.151
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发表时间：
2003-12
期刊：
影响因子：
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通讯作者：
B. Xiao;H. Xu;Yucan Fu;Jiu-hua Xu
中科院分区：
文献类型：
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作者：
B. Xiao;H. Xu;Yucan Fu;Jiu-hua Xu
为了揭示Ni-Cr合金钎焊金刚石界面合成物的大小、数量、形态和分布特征，进行了真空炉钎焊。SEM-EDS微分析表明，在钎焊过程中，合金中的铬优先偏析到金刚石表面，形成富铬反应产物。x射线衍射结果表明，高温下Ni-Cr合金中的Cr原子与金刚石表面的C原子相互作用产生Cr3C2和Cr7C3，从而实现了Ni-Cr合金熔液在金刚石表面的润湿键合行为。此外，还发现了Cr3C2和Cr7C3的尺寸、数量、形态和分布特征，阐明了金刚石钎焊机理。钎焊金刚石工具越来越受到人们的重视，其中单层钎焊金刚石工具作为一种新型工具诞生并开始实际应用。在单层钎焊工具中，钎焊界面合成物的大小、数量、形态和分布特征是决定钎焊材料粘附性能和使用寿命的关键因素。钎焊金刚石的主要结合方法是利用含Cr、Ti、Mo、Zr或V等均为碳化物形成金属的合金作为钎焊材料，然后在真空或惰性气氛中将金刚石钎焊在金属基体上。利用加工试验评价切削工具或磨削工具的性能的文章很多，但对钎焊金刚石界面合力的形成和分布特征的讨论却很少。因此，本研究的基本目的是研究真空炉钎焊过程中镍铬合金钎焊金刚石界面结的形成和分布特征。实验方法采用适当成分的镍铬合金进行钎焊。将上述合金涂在钢的上表面，然后在上面撒上金刚石砂。在真空气氛下，在中等温度下进行钎焊。通过扫描电镜观察到的钎焊金刚石外观如图1所示。结果表明：金刚石磨粒被有效润湿，磨粒的突出高度可达到其粒径的2/3以上；SEM-EDS显微分析（图2）表明，合金中的铬在钎焊过程中向金刚石表面析出，很可能形成碳化铬。表1中的热力学数据清楚地表明碳化铬的化学稳定性比金刚石高。因此，在普遍钎焊条件下，界面处碳化铬的形成是很有希望的。关键工程材料在线：2004-03-15 ISSN: 1662-9795， vol .259-260, pp 151-153 doi:10.4028/www.scientific.net/KEM.259-260.151©2004 Trans Tech Publications Ltd， Switzerland版权所有。未经Trans Tech Publications Ltd， www.scientific.net的书面许可，不得以任何形式或任何方式复制或传播本文的部分内容。(Semanticscholar.org-13/03/20 19:03:37) 152年的进步磨削和研磨过程图1润湿和金刚石磨粒的粘结镍铬合金浓度图2曲线界面元素的镍铬合金和钻石表1自由能的形成和碳化铬和钻石的生成热在298 k的生成自由能(千卡·摩尔(1)的生成热(千卡·摩尔(1)钻石-39.9 - -38.7 0.6850 - 0.4532 -19.5 - -19.3 Cr3C2 Cr7C3 Cr23C6 -89.3 - -87.2的样子Ni-Cr合金钎料与钢基体化学腐蚀后，通过SEM观察到的钎焊金刚石表面的合力如图3所示。金刚石砂明显被界面产物所覆盖。为了揭示钎焊金刚石界面合成物的类型和结构特征，进行了x射线衍射分析。从图4可以看出，高温下Ni-Cr合金中的Cr原子与金刚石表面的C原子相互作用产生Cr3C2、Cr7C3和Cr23C6，从而实现了Ni-Cr合金熔液在金刚石表面的润湿和键合行为。图5显示了Cr3C2和Cr7C3的形态和分布特征。此外，从图5可以看出，生成的界面由内到外的顺序为Cr3C2 Cr7C3 Cr23C6。金刚石界面Ni-Cr 152磨削磨料研究进展
In order to reveal the size, number, form and distribution characterization of resultant at the brazing diamond interface using Ni-Cr alloy, vacuum furnace brazing was carried out. SEM-EDS microanalyses have shown that during brazing the chromium present in the alloy segregated preferentially to the surface of the diamond to form a chromium-rich reaction product. X-ray diffraction revealed that the wetting and bonding behaviour on diamond surface by molten Ni-Cr alloy is realized through Cr3C2 and Cr7C3 which are produced by interaction between Cr atoms of Ni-Cr alloy and C atoms of diamond surface at elevated temperatures. Furthermore, the size, number, form and distribution characterization of Cr3C2 and Cr7C3 were discovered and the brazing mechanism for diamond was illuminated. Introduction Much attention has been paid to brazed diamond tools, among which mono-layer tools are born and come into practical use as a new tool. In mono-layer tools, the size, number, form and distribution characterization of resultant at the brazing interface are key factors to determine the adhesion performance and service life. The main bonding method used for brazing diamond is to utilize alloy containing Cr, Ti, Mo, Zr or V, which are all carbide-forming metals, as brazing materials, and then to braze diamond on a metal substrate in vacuum or inert atmosphere. Many papers have reported on the performance evaluation of cutting or grinding tools by machining test, but few have been found to discuss the form and distribution characterization of resultant at the brazing diamond interface. Therefore the basic objective of the present work was the study on the form and distribution characterization of resultant at the brazing diamond interface using Ni-Cr alloy during vacuum furnace brazing. Experimental Procedure Ni-Cr alloy with a suitable composition was used for brazing purpose. The said alloy was applied on the top surface of the steel, followed by sprinkling of diamond grits on it. The brazing was carried out under vacuum atmosphere at moderate temperature. Results and Discussion The appearance of brazing diamond observed by SEM was shown in Fig.1. The result illustrated that diamond grits were effectively wetted and protrusion height of grit could reach more than 2/3 of its size. SEM-EDS microanalyses (Fig.2) have shown that the chromium present in the alloy segregated during brazing towards the diamond surface, most probably to form chromium carbide. The thermodynamic data presented in Table 1 clearly indicate a high chemical stability of chromium carbide than that of diamond. Therefore under the prevalent brazing condition the formation of chromium carbide at the interface is quite expected. Key Engineering Materials Online: 2004-03-15 ISSN: 1662-9795, Vols. 259-260, pp 151-153 doi:10.4028/www.scientific.net/KEM.259-260.151 © 2004 Trans Tech Publications Ltd, Switzerland All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications Ltd, www.scientific.net. (Semanticscholar.org-13/03/20,19:03:37) 152 Advances in Grinding and Abrasive Processes Fig.1 Wetting and bonding of diamond grits by Ni-Cr alloy Fig.2 Concentration curves of elements at the interface of Ni-Cr alloy and diamond Table 1 Free energy of formation and heat of formation of chromium carbide and diamond at 298K Free energy of formation [Kcal·mol -1 ] Heat of formation [Kcal·mol -1 ] Diamond 0.6850 0.4532 Cr3C2 -19.5 -19.3 Cr7C3 -39.9 -38.7 Cr23C6 -89.3 -87.2 The appearance of resultant at the surface of brazing diamond observed by SEM after chemical corrosion of Ni-Cr alloy filler and steel substrate was shown in Fig.3. Obviously diamond grit was covered with the interface resultant. In order to reveal the type and structure characterization of resultant at the brazing diamond interface X-ray diffraction was carried out. Fig.4 reveals that the wetting and bonding behaviour on diamond surface by molten Ni-Cr alloy is realized through Cr3C2, Cr7C3 and Cr23C6 which are produced by interaction between Cr atoms of Ni-Cr alloy and C atoms of diamond surface at elevated temperatures. Fig.5 shows the form and distribution characterization of Cr3C2 and Cr7C3. Furthermore, Fig.5 reveals the sequence from interior to exterior of the interface resultant is Cr3C2 Cr7C3 Cr23C6. Diamond Interface Ni-Cr 152 Advances in Grinding and Abrasive Processes