發(fā)布時(shí)間：2018-06-24 01:26

  本文選題：截齒 + 等離子堆焊��； 參考：《中北大學(xué)》2017年碩士論文

【摘要】：礦用截齒是采煤機(jī)上用來(lái)割煤、鑿巖的刀具。截齒在工作過(guò)程中,受到煤層的周期性沖擊、劇烈摩擦和擠壓以及合金內(nèi)部交變熱應(yīng)力等多種因素的綜合作用,其失效比較嚴(yán)重,必須進(jìn)行修復(fù)或更換。礦用截齒的主要失效形式有:磨損、崩刃、碎裂及斷裂,其中磨損失效是截齒失效的最主要形式。因此,提高截齒的耐磨性,延長(zhǎng)其使用壽命具有重要意義。本文采用等離子堆焊技術(shù),在中碳低合金鋼表面堆焊一層不同質(zhì)量比的Ni60、WC、Cr3C2和TiC合金粉末,通過(guò)實(shí)驗(yàn)試圖找到強(qiáng)化截齒表面性能的最優(yōu)合金粉末。使用光學(xué)金相顯微鏡、掃描電子顯微鏡+能譜儀、X射線衍射儀、顯微硬度計(jì)對(duì)堆焊層進(jìn)行微觀組織結(jié)構(gòu)及硬度分析。使用沖擊磨粒磨損實(shí)驗(yàn)機(jī)對(duì)堆焊層的耐磨性能進(jìn)行了研究,同時(shí)利用掃描電鏡,對(duì)磨損形貌進(jìn)行觀察,研究其磨損機(jī)理。結(jié)果表明:在顯微組織方面,堆焊層中出現(xiàn)了魚(yú)骨狀、蜘蛛網(wǎng)狀、碎花狀組織,此外,四個(gè)試樣堆焊層熔合層出現(xiàn)大量針狀馬氏體,并帶有少量的奧氏體,3號(hào)試樣堆焊層的中間層存在較多的奧氏體。XRD分析得出,堆焊層主要由Ni-Cr-Fe奧氏體相,硼化物硬質(zhì)相CrB、Ni4B,碳化物硬質(zhì)相WC、W3C、Cr7C3、TiC等組成。TiC密度小,含量較少,堆焊過(guò)程中,熔化充分,主要分布在堆焊層表層及中間層,即從堆焊表層向熔合線附近逐漸減少。相比碳化鈦,碳化鎢、碳化鉻的密度較大,在熔合層附近出現(xiàn)沒(méi)有完全熔化的碳化鎢、碳化鉻顆粒。顯微硬度沿著熔合線至表面方向呈梯度變化,中間層區(qū)域的硬度比熔合層附近堆焊層的硬度略有降低,到了表層區(qū)域附近硬度有所上升。耐磨性方面,在同種工況條件下對(duì)四個(gè)試樣進(jìn)行耐磨性實(shí)驗(yàn),結(jié)果顯示:隨著時(shí)間的進(jìn)行,磨損量不斷增加。磨損前期質(zhì)量損失小,中期質(zhì)量損失大,后期質(zhì)量損失小,劇烈磨損點(diǎn)均出現(xiàn)在磨損中期。其中1號(hào)試樣磨損量最大,2號(hào)和3號(hào)試樣磨損量較少,基本一致,耐磨性較強(qiáng)。4號(hào)試樣磨損量最少,耐磨性最強(qiáng)。通過(guò)掃描電子顯微鏡觀察,四個(gè)試樣堆焊層磨損機(jī)制以磨粒磨損、疲勞磨損和粘著磨損為主。此外,磨損過(guò)程中試樣表面均出現(xiàn)脫落坑、微裂紋、犁溝等磨損缺陷。
[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.
【學(xué)位授予單位】：中北大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TD421.6;TG455

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本文編號(hào)：2059346