【作者】 张旭；

【导师】 李惠琪；

【作者基本信息】 山东科技大学 ， 材料学， 2011， 硕士

【摘要】 硬质合金具有特殊的耐腐蚀性、高硬度、优良的断裂韧性和抗压强度,目前全世界生产的硬质合金中以WC硬质合金牌号最多、产量最大,用途也最为广泛。在传统工艺中,截齿用硬质合金的生产方法是粉末冶金技术,经过WC粉和钴粉混合压制烧结而成。粉末冶金技术对原料WC粉末的纯度、粒度均匀性,以及颗粒形貌、结晶完整性、亚晶尺寸大小等都有很高的要求,生产工艺复杂。与传统工艺的先制取WC粉末,继而烧结成硬质合金不同,本论文提出利用等离子原位冶金技术在截齿盲孔内由WO3或w制备截齿WC块体耐磨材料的新方法。使用该法制备块体耐磨材料的优点在于：(1)成本低,原料粉末以W03或w和炭黑为主；(2)短流程,直接在截齿盲孔内生成块体耐磨材料,取代了粉末冶金的复杂工艺；(3)冶金结合,避免了钎焊硬质合金带来的各种问题。本论文利用热力学第二定律,通过曲线外延法证明了在超高温下由W03或w制备WC的可行性。反应温度大于1000K时,C与W03可能发生固—固反应、液—固反应、铁浴反应、液—液反应,以上反应均为吸热反应,随着温度的上升,利于反应的正向进行。C与W生成WC的反应是放热反应,但当AG=0时,Tc>22000K,高于等离子原位冶金反应温度,故而反应也可以进行。在试验中由W03制备的块体耐磨材料,裂痕较多,成形性差,未能达到预期结果；由w试制的块体耐磨材料成型及致密性较好,最高硬度可达1987HV。WC晶粒呈聚集状态随机分布,其生成方式为台阶式逐步生长,除WC晶粒外,块体耐磨材料中还有M6C(Fe3W3C-Fe4W2C),Cr7C3,(Fe,Cr,Ni)3C和γ-Fe等物相,其中M6C是块体耐磨材料中主要的硬质相；块体耐磨材料中含有大量的w元素,显著提高了合金的抗腐蚀磨损能力；由W、Cr、Fe形成的碳化物作为主要硬质相弥散分布在齿体当中,对WC相起到良好的支撑作用,因此实现了高的显微硬度。对耐磨材料的成分、组织、性能进行了检测和分析,结果表明：由W制备的块体耐磨材料的硬度、耐磨性初步达到预期目标,整体平均显微硬度1254HV(载荷200g,保持时间10s),相对耐磨性0.83(参比样YG13C)。本论文对该法的工业应用进行了可行性评估,认为该法在成本和工艺上的具有巨大优势,在截齿制造领域将有广阔的应用前景。更多还原

【Abstract】 Currently, the wear-resistant materials of picks are coarse-grained WC carbide. Carbide has a special corrosion resistance, high hardness, excellent fracture toughness and compre-ssion strength, called modern industrial teeth. The most widely use of the cemented carbide is WC carbide. In the traditional process, the production of cemented carbide picks is sintered by the WC and cobalt, but that process is complicated.Different from the traditional process, this paper proposes using the plasma situ metallurgical technology preparation of the wear-resistant block materials in the blind hole of picks. This is a new method of preparation of making wear-resistant materials. There are three advantages of this new method. Firstly, low cost, raw materials are W or WO3 powder and carbon powder. Secondly, short process, replacing the complexity of powder metallurgy technology, wear-resistant materials directly generated in the picks block. Thirdly, achieve metallurgical bonding, avoiding the problems caused by brazing carbide.In this paper, it is proved that in the WC by the preparation of the feasibility of WO3 in ultra-high temperatures by using the second law of thermodynamics. When more than 1000K, C and WO3 may be solid-solid reaction, liquid-liquid reaction, iron bath reaction, liquid-liquid reactions, and all of those are endothermic reactions, as the temperature increased, the positive reactions were favorable, but WO3 trial in the experiment of the block by the wear-resistant materials, cracks are more poor shape, did not achieve the expected results.The density of wear-resistant materials bulk prepared by the W is better, WC grains are randomly distributed aggregation, the maximum hardness is more than 1987HV, WC crystal grain size is generated by the way of step-phase growth; addition to WC grain size, there are M6C (Fe3W3C-Fe4W2C),Cr7C3, (Fe,Cr,Ni)3C and y-Fe in the wear-resistant materials in the bulk phase. M6C in which wear-resistant materials is the main hard phase, the overall average micro hardness is 1254HV, the block contains a lot of wear-resistant just like the W elements, significantly increases the resistance of corrosion and wear ability; Formed by W, Cr, Fe which as the main hard phase dispersed points distributed in the picks body, the carbides play a good supporting role on the WC phase, to achieve a high hardness and wear resistance. Wear-resistant materials were tested and analyzed on the composition, microstruture, properties, the results showed that, wear-resistant materials prepared by the W hardness, wear resistance initially meet the target, and has good mechanical properties of strength and toughness. This method has the advantage of the process and cost, it will certainly have a great prospect in picks manufacturing.更多还原