堆焊硬面合金中碳氮化物质点对其组织和性能的影响

发布时间：2018-01-03 14:40

  本文关键词：堆焊硬面合金中碳氮化物质点对其组织和性能的影响　出处：《华中科技大学》2015年硕士论文　论文类型：学位论文

  更多相关文章： 马氏体不锈钢 药芯焊丝 碳氮化物 组织 性能

【摘要】：现广泛使用的硬面药芯焊丝主要是利用碳与铬、钛、铝、钒、铌等形成碳化物硬质点,来提高硬面合金的硬度和耐磨性。由于药芯焊丝中含碳量较高、合金元素较多,导致堆焊层的碳当量较高,使其产生裂纹的趋势明显升高,再加上高碳硬面药芯焊丝堆焊层中的碳化物常呈板条状,这些板条状碳化物容易在晶界聚集,造成其成分的分布不均匀,使堆焊层硬面合金的塑性降低,使用过程中容易剥落,使得与其本应该起的作用背道而驰。本课题针对传统硬面合金的不足,结合堆焊工艺,以Cr13马氏体不锈钢为研究对象,提出用氮代替部分碳进行氮合金化,获得足够多数量弥散分布的碳氮化物硬质相质点。利用这些弥散分布的碳氮化物硬质相来提高机械零件耐磨粒磨损性能和耐高温磨损性能。通过优化焊接工艺规范,在Q235钢板上堆焊5道4层。用化学成分分析仪分析堆焊层熔敷金属成分及含量,用高温摄影仪观察熔敷金属在加热和冷却过程中组织变化规律,对截取试样在450℃~600℃不同温度下回火热处理,用洛氏硬度计测量硬度,用金相显微镜观察显微组织,用自制磨粒磨损试验机测量磨损失重,用高温磨损试验机测量试样在500℃高温下磨损失重,用扫描电镜观察堆焊层微观组织和磨损形貌,用电子探针对第二相粒子和磨屑进行能谱点分析,研究结果如下:(1)所研制的硬面药芯焊丝堆焊层组织为马氏体+残余奥氏体,同时在基体和晶界分布着均匀细小的碳氮化物(Nb、V、Cr)x(C、N)y,且硬面合金组织随着氮化铬和氮化物形成元素钒、铌的加入而细化,当氮化铬添加量超过一定值时,堆焊层将形成氮气孔。(2)药芯焊丝中仅添加氮化铬,堆焊层硬度变化不大,当添加钒、铌后,焊态下堆焊层硬度随着氮化铬含量的增加而增加。对堆焊层金属进行回火热处理时,当回火温度在450℃以下时,堆焊层硬度几乎没有变化;当回火温度为480℃时,堆焊层硬度略有下降;继续提高回火温度,堆焊层硬度先回升后降低。(3)在药芯焊丝中添加2%铌铁、2%钒铁和5%氮化铬,焊态下堆焊层耐磨粒磨损性能比碳合金化硬面合金提高约30%。采用合适的热处理方案,氮合金化硬面合金堆焊层耐磨粒磨损性能比未热处理时提高约15%,比碳合金化硬面合金堆焊层的耐磨粒磨损性能提高约35%。(4)高温磨损的主要失效形式为高温氧化皮的剥落、摩擦磨损和磨粒磨损,药芯焊丝中添加钒铁、铌铁和氮化铬可有效提高堆焊层焊态下的耐高温磨损性能。在磨损环境温度为500℃时,500℃以下回火热处理对堆焊层耐高温磨损性能影响不大,500℃以上回火热处理,碳合金化硬面合金堆焊层耐高温磨损性能不断下降,而氮合金化硬面合金堆焊层耐高温磨损性能先提高后降低。
[Abstract]:The hard cored wire which is widely used now mainly uses carbon and chromium, titanium, aluminum, vanadium, niobium and so on to form carbide hard spots, to improve the hardness and wear resistance of hard face alloy, because of the high carbon content in the flux cored wire. With more alloy elements, the carbon equivalent of the surfacing layer is higher, and the tendency of cracks is obviously increased. In addition, the carbides in the surfacing layer of high carbon hard cored wire are often in the shape of sheet. These carbides are easily accumulated at grain boundaries, resulting in the uneven distribution of the composition, which reduces the plasticity of hardfacing alloys in the surfacing layer and is easy to peel off in the process of use. This subject aims at the shortage of traditional hard alloy, combined with surfacing welding technology, taking Cr13 martensitic stainless steel as the research object. Nitrogen is used instead of carbon for nitrogen alloying. A sufficient number of carbon and nitride hard phase particles were obtained, which were used to improve the wear resistance and high temperature wear resistance of mechanical parts. By optimizing the welding process rules, the wear resistance and wear resistance of mechanical parts were improved. Van. The composition and content of cladding metal were analyzed by chemical composition analyzer. The microstructure of deposited metal during heating and cooling was observed by high temperature photography. The samples were annealed at 450 鈩，

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