原位复合(Nb-Cr-Ti)C堆焊金属的组织与性能

Microstructure and Properties of In-Situ Synthesized Nb-Cr-Ti/C Surfacing Welded Metal

工业机械设备表层磨损失效非常普遍,堆焊是其最有效的保护方法之一。采用自制焊条,通过对堆焊合金的组织结构设计和成分调整,自行设计了Nb-Cr-Ti系堆焊金属,并堆焊出了耐磨抗裂的合金层。采用光学显微镜、扫描电镜、能谱分析仪器以及磨损试验机等,分析了堆焊层组织结构和性能,探讨了各合金元素在堆焊层中的作用。结果表明:堆焊层组织为混合型马氏体和少量残余奥氏体+弥散分布的复合(Nb-Cr-Ti)C颗粒,低碳马氏体和高碳马氏体数量相当。铌在高温下先析出生成硬质相NbC,碳化物硬质点呈颗粒状弥散分布,使组织细化,也使焊层达到较高的硬度,提高了耐磨性。碳化物的大量弥散析出,使得基相含碳量较低而转变成低碳马氏体,因基相有较高的塑韧性,抗裂性增强。该堆焊层的耐磨性和抗裂性明显优于商用D667焊条。

The worn and failed surface of workpieces made of 0235 steel can be effectively rebuilt bv hardfacing.Thus wear- and crack-resistant Nb-Cr-Ti/C surfacing welded coating was prepared on the surface of the steel by using the welding rods and by conducting design of microstructure and manipulation of composition.The microstruerure and properties of Nb-Cr-Ti hardfacing coating were analyzed bv means of optical microscopy, scanning electron microscopy, energy dispersive spectrometry, and dry sand abrasion test.And the function of various alloy elements in the hardfacing coating was explored.Results show that the hardfacing coating is composed of martensite mixed with a small amount of residued austenite, and Nb-Cr-Ti/C is well dispersed in the matrix.At the same time, the amount of low-carbon martensite was comparable to that of high-carbon martensite.Nb precipitated firstly forming NbC phase, contributing to refined structure and improved wear resistance of the hardfacing coating.The dispersed precipitation of a large amount of carbides led to reduced content of carbon in the matrix and transformation of the matrix to low carbon martensite.And the matrix with good plasticity and toughness was helpful to improve the crack-resistance.In one word.the present hardfacing coating has better wear- and crack-resistance than that obtained from commercial D667 welding rod.