本文選題：超硬材料 + 立方氮化硼　； 參考：《山東大學(xué)》2017年碩士論文

【摘要】：立方氮化硼(cBN)是一種硬度僅次于金剛石的材料,具有優(yōu)異的機(jī)械、電學(xué)、光學(xué)和熱學(xué)性能,在各種高新科技領(lǐng)域具有重要的研究和應(yīng)用價(jià)值。聚晶立方氮化硼(PcBN)以cBN單晶為主要原材料,在高溫高壓下燒結(jié)而成,是一種應(yīng)用廣泛的刀具材料。在PcBN的燒結(jié)過程中,粘結(jié)劑作為一個(gè)重要的影響因素,與cBN單晶相互作用,對PcBN的性能有很大影響,具有重要的研究價(jià)值。合成PcBN的粘結(jié)劑有很多種,主要包括金屬粘結(jié)劑,陶瓷粘結(jié)劑以及一些其它粘結(jié)劑。本文選取了較為常見的金屬鋁(Al)和陶瓷碳化鈦(TiC),以及新型三元過渡族金屬碳化物鈦碳化硅(Ti3SiC2)和鈦碳化鋁(Ti3AlC2)分別作為粘結(jié)劑材料用來合成PcBN塊體材料。分析研究了 PcBN的成分、抗彎強(qiáng)度、抗壓強(qiáng)度、硬度以及熱穩(wěn)定性。研究發(fā)現(xiàn),當(dāng)以Al作為粘結(jié)劑時(shí),Al會與cBN在高溫高壓下發(fā)生反應(yīng),生成AlN和AlB2等物質(zhì)。隨著Al的添加量從5 wt.%增加到10 wt.%,后增加至20 wt.%,所合成的PcBN的抗彎強(qiáng)度和抗壓強(qiáng)度表現(xiàn)出先降低,后增大的趨勢。燒結(jié)過程中所產(chǎn)生的AlN和AlB2對整體PcBN有粘結(jié)作用,同時(shí)也是斷裂容易發(fā)生的地方。而當(dāng)TiC作為粘結(jié)劑時(shí),由于TiC惰性強(qiáng),熔點(diǎn)高,TiC和cBN之間并未發(fā)生反應(yīng),所合成的PcBN仍然由cBN和TiC組成。添加10 wt.%的TiC可使合成的最致密的結(jié)構(gòu),同時(shí)可使燒結(jié)得到的PcBN具有較好的機(jī)械性能。當(dāng)以Ti3AlC2或Ti3SiC2作為粘結(jié)劑在高溫高壓下燒結(jié)PcBN時(shí),在燒結(jié)過程,Ti3AlC2或Ti3SiC2會分解并與cBN發(fā)生反應(yīng),并最終生成TiC,TiC0.7N0.3,TiB2,SiC以及AlN等物質(zhì)。對于cBN-Ti3AlC2燒結(jié)組來說,當(dāng)添加20 wt.%Ti3AlC2時(shí),燒結(jié)出的PcBN具有最致密的結(jié)構(gòu),同時(shí)具有最高的抗彎強(qiáng)度、抗壓強(qiáng)度以及硬度。而當(dāng)以Ti3SiC2為粘結(jié)劑時(shí),當(dāng)添加10wt.%Ti3SiC2時(shí),燒結(jié)出的PcBN具有最高的抗彎強(qiáng)度;添加20wt.%Ti3SiC2時(shí),PcBN具有最高的抗壓強(qiáng)度;而添加40 wt.%Ti3SiC2時(shí),PcBN具有最高的硬度和最致密的結(jié)構(gòu)。對于這四種粘結(jié)劑所合成的PcBN,各取一個(gè)試樣進(jìn)行熱分析,并且分析了氧化后的表面成分。氧化過后,PcBN表面會形成Al和Ti等的氧化物層,并伴隨著裂紋的出現(xiàn)。盡管氧化層不夠致密,但能對PcBN材料內(nèi)部起到一定的保護(hù)作用。
[Abstract]:Cubic boron nitride (CBN) is a kind of material whose hardness is second only to diamond. It has excellent mechanical, electrical, optical and thermal properties, and has important research and application value in various high-tech fields.Polycrystalline cubic boron nitride (PcBN) is a widely used tool material, which is sintered at high temperature and high pressure using cBN single crystal as the main raw material.In the sintering process of PcBN, the interaction between binder and cBN single crystal, as an important influence factor, has great influence on the properties of PcBN and has important research value.There are many kinds of binders for the synthesis of PcBN, including metal binders, ceramic binders and some other binders.In this paper, the more common metal Al) and the ceramic titanium carbide TiCX, as well as the new ternary transition metal carbides Ti3SiC2) and the Ti3AlC2Ti3AlC2) are used as binders to synthesize PcBN bulk materials, respectively.The composition, bending strength, compressive strength, hardness and thermal stability of PcBN were studied.It is found that when Al is used as binder, Al can react with cBN at high temperature and high pressure to form AlN and AlB2.With the increase of Al content from 5wt.% to 10wt.and then to 20wt.k., the bending strength and compressive strength of the synthesized PcBN show a tendency of first decreasing and then increasing.The AlN and AlB2 produced in the sintering process have bond effect on the whole PcBN and are also the places where the fracture is easy to occur.However, when TiC is used as binder, because of the strong inertness of TiC, there is no reaction between tic and cBN with high melting point, and the synthesized PcBN is still composed of cBN and TiC.Adding 10 wt.% TiC can make the synthesized PcBN have the densest structure and the sintered PcBN has better mechanical properties.When PcBN is sintered with Ti3AlC2 or Ti3SiC2 as binder at high temperature and high pressure, Ti3AlC2 or Ti3SiC2 will decompose and react with cBN during sintering, and finally, TiC0. 7N0. 3TIB 2 sic and AlN will be formed.For the cBN-Ti3AlC2 sintering group, the sintered PcBN has the densest structure and the highest bending strength, compressive strength and hardness when 20 wt.%Ti3AlC2 is added.When Ti3SiC2 is used as binder, PcBN sintered has the highest bending strength when 10wt.%Ti3SiC2 is added, 20wt.%Ti3SiC2 has the highest compressive strength, and PcBN with 40 wt.%Ti3SiC2 has the highest hardness and the densest structure.For the PcBNs synthesized by these four binders, one sample was taken for thermal analysis and the surface composition after oxidation was analyzed.After oxidation, oxide layers such as Al and Ti are formed on the surface of PcBN, and the cracks appear.Although the oxide layer is not compact enough, it can protect the PcBN material.
【學(xué)位授予單位】：山東大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TB33

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本文編號：1733987