矿用截齿等离子堆焊层耐磨性能研究

发布时间：2018-06-24 01:26

本文选题：截齿 + 等离子堆焊　；参考：《中北大学》2017年硕士论文

【摘要】：矿用截齿是采煤机上用来割煤、凿岩的刀具。截齿在工作过程中,受到煤层的周期性冲击、剧烈摩擦和挤压以及合金内部交变热应力等多种因素的综合作用,其失效比较严重,必须进行修复或更换。矿用截齿的主要失效形式有:磨损、崩刃、碎裂及断裂,其中磨损失效是截齿失效的最主要形式。因此,提高截齿的耐磨性,延长其使用寿命具有重要意义。本文采用等离子堆焊技术,在中碳低合金钢表面堆焊一层不同质量比的Ni60、WC、Cr3C2和TiC合金粉末,通过实验试图找到强化截齿表面性能的最优合金粉末。使用光学金相显微镜、扫描电子显微镜+能谱仪、X射线衍射仪、显微硬度计对堆焊层进行微观组织结构及硬度分析。使用冲击磨粒磨损实验机对堆焊层的耐磨性能进行了研究,同时利用扫描电镜,对磨损形貌进行观察,研究其磨损机理。结果表明:在显微组织方面,堆焊层中出现了鱼骨状、蜘蛛网状、碎花状组织,此外,四个试样堆焊层熔合层出现大量针状马氏体,并带有少量的奥氏体,3号试样堆焊层的中间层存在较多的奥氏体。XRD分析得出,堆焊层主要由Ni-Cr-Fe奥氏体相,硼化物硬质相CrB、Ni4B,碳化物硬质相WC、W3C、Cr7C3、TiC等组成。TiC密度小,含量较少,堆焊过程中,熔化充分,主要分布在堆焊层表层及中间层,即从堆焊表层向熔合线附近逐渐减少。相比碳化钛,碳化钨、碳化铬的密度较大,在熔合层附近出现没有完全熔化的碳化钨、碳化铬颗粒。显微硬度沿着熔合线至表面方向呈梯度变化,中间层区域的硬度比熔合层附近堆焊层的硬度略有降低,到了表层区域附近硬度有所上升。耐磨性方面,在同种工况条件下对四个试样进行耐磨性实验,结果显示:随着时间的进行,磨损量不断增加。磨损前期质量损失小,中期质量损失大,后期质量损失小,剧烈磨损点均出现在磨损中期。其中1号试样磨损量最大,2号和3号试样磨损量较少,基本一致,耐磨性较强。4号试样磨损量最少,耐磨性最强。通过扫描电子显微镜观察,四个试样堆焊层磨损机制以磨粒磨损、疲劳磨损和粘着磨损为主。此外,磨损过程中试样表面均出现脱落坑、微裂纹、犁沟等磨损缺陷。
[Abstract]:Mining cutter is the cutting tool for cutting coal and drilling rock on the shearer. In the process of working, the teeth are subjected to periodic impact of coal seam, severe friction and extrusion, internal alternating thermal stress and other factors, its failure is serious, it must be repaired or replaced. The main failure forms of mine cutter are wear, breakage, fragmentation and fracture, among which wear failure is the main form of tooth cutting failure. Therefore, it is of great significance to improve the wear resistance and prolong its service life. In this paper, plasma surfacing technology is used to surfacing a layer of Ni60WCtCr3C2 and tic alloy powder with different mass ratio on the surface of medium carbon low alloy steel. The microstructure and hardness of the surfacing layer were analyzed by means of optical metallographic microscope, scanning electron microscope energy spectrometer and X-ray diffractometer. The wear resistance of the surfacing layer was studied by impact abrasive wear tester. The wear morphology was observed by scanning electron microscope (SEM) and the wear mechanism was studied. The results show that the microstructure of the surfacing layer is fishbone, spider mesh and broken flower. In addition, a large amount of needle martensite appears in the fusion layer of the four sample surfacing layers. With a small amount of austenite, there is more austenite. XRD analysis shows that the surfacing layer is mainly composed of Ni-Cr-Fe austenite phase, boride hard phase CrBN Ni4B, carbide hard phase WCC3C0Cr7C3TiC and so on. In the process of surfacing welding, the melting is sufficient, mainly distributed in the surfacing layer and the middle layer, that is, from the surfacing layer to the fusion line. Compared with titanium carbide, tungsten carbide and chromium carbide, the density of chromium carbide is higher than that of titanium carbide, and there are not completely melted tungsten carbide and chromium carbide particles near the fusion layer. The hardness of the middle layer is slightly lower than that of the surfacing layer near the fusion layer, and the hardness of the surfacing layer increases slightly near the surface layer. In the aspect of wear resistance, four samples were tested under the same working conditions. The results showed that the wear amount increased with time. The mass loss in the early wear stage is small, the mass loss in the middle period is large, and the mass loss in the later period is small. The severe wear points appear in the middle wear period. The wear capacity of specimen No. 1 is the largest, that of specimen No. 2 and sample No. 3 is less, and the wear resistance of specimen No. 4 is the least, and the wear resistance of specimen No. 4 is the strongest. The wear mechanism of surfacing layer of four samples was mainly abrasive wear fatigue wear and adhesive wear observed by scanning electron microscope. In addition, the wear defects such as shedding pits, microcracks and ploughs appeared on the surface of the specimens during wear.
【学位授予单位】：中北大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD421.6;TG455

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