摘要
采用激光熔覆技术,通过调节Nb含量制备多组Fe-Cr-Nb-C合金。利用扫描电子显微镜(SEM)、 X射线衍射仪(XRD)、显微硬度计、洛氏硬度计和磨粒磨损试验机等设备分析比较了不同Nb含量对Fe-Cr-Nb-C熔覆层组织和耐磨性的影响。试验及分析结果表明:熔覆层表面组织由铁素体、奥氏体、 M7C3和NbC组成;随着合金中Nb含量的增加,断续网状M7C3相的数量逐渐减少, NbC的数量逐渐增多,且形态逐渐由树枝状向点状转变,当w(Nb)达到5.4%时, NbC的数量达到最高值且在熔覆层表面基体中呈均匀分布;熔覆层横截面显微硬度呈梯度分布,表层平均硬度的最高值达到HV0.2600~HV0.2910。在一定范围内,熔覆层的耐磨性随着Nb含量的增加呈先降低后显著提高的趋势,当w(Nb)为5.4%时,大量晶粒适中的点状NbC均匀弥散分布在铁素体和奥氏体基体上,使得熔覆层具有最佳的耐磨性。
A series of Fe-Cr-Nb-C hardfacing alloys with different niobium contents were prepared by laser cladding.The effects of addition amount of Nb on microstructure and wear resistance of cladding layers were investigated by means of scanning electron microscopy,X-ray diffraction,microhardness tester,Rockwell apparatus and abrasive wear tester.The results showed that the microstructure of cladding layers were composed of ferrite, austenite,M7C3and NbC.With the volume fraction of interrupted netted M7C3 complex carbides decreased,the volume fraction of NbC increased and the morphology changed from dendritic to globular shape as Nb content increased,the maximum volume fraction of primary NbC were attained and primary NbC were distributed uniformly in the matrix when the Nb content reached 5.4%.The microhardness of the cladding layer cross section appeared reasonable gradient distribution,the microhardness of the surface layer reached HV0.2600-HV0.2910.The wear resistance of cladding layers decreased and then increased significantly with the increasing amount of Nb.When Nb content was 5.4%,the microstructure characteristic with a high volume fraction of globular NbC with appropriate grain size were distributed uniformly and dispersly in the ferrite and austenite matrix,which suggested that the cladding layer had a excellent wear resistance.
作者
宗琳
张小玲
ZONG Lin;ZHANG Xiao-ling(School of Mechanical Engineering,Shenyang University of Chemical Technology,Shenyang 110142,Liaoning pro.,China)
出处
《焊接技术》
2018年第11期26-30,I0001,共6页
Welding Technology
基金
辽宁省教育厅科学技术研究一般项目(LQ2017014)
辽宁省自然科学基金研究项目(20180551117)
关键词
激光熔覆
耐磨性
组织
NBC
laser cladding
wear resistance
microstructure
NbC
