本文選題：人造金剛石單晶 + 熱化學(xué)腐蝕�。� 參考：《湖南大學(xué)》2016年博士論文

【摘要】：金剛石由于具有很高的硬度、耐磨性及較強(qiáng)的化學(xué)惰性,因而作為磨粒在硬脆材料加工領(lǐng)域得到廣泛的應(yīng)用。人造金剛石顆粒尺寸較小,通常采用結(jié)合劑將它們粘結(jié)起來制備成具有一定形狀、大小和強(qiáng)度的工具。但由于金剛石單晶表面光滑且表面能較高,在制備金剛石工具時(shí)結(jié)合劑很難潤濕金剛石。因此,兩者之間主要以機(jī)械鑲嵌為主,結(jié)合力較弱,磨削加工時(shí)大部分金剛石由于過早脫落而造成非磨削損耗。為了提高結(jié)合劑對金剛石的把持力,目前采用的方法主要是對金剛石表面進(jìn)行鍍覆或涂覆處理。針對這些處理技術(shù)的局限性,論文采用熱化學(xué)法以鐵族金屬及其鹽對金剛石單晶進(jìn)行腐蝕。系統(tǒng)研究了各參數(shù)變化對鐵族金屬粉末腐蝕金剛石單晶的影響規(guī)律,結(jié)合熱力學(xué)計(jì)算,探討了鐵族金屬腐蝕金剛石單晶的主要機(jī)理;考察了鐵族金屬鹽在不同溫度下對金剛石單晶的腐蝕及主要機(jī)制;將不同方法處理的金剛石分別與銅基和鐵基金屬結(jié)合劑制備成鋸片,對鋸片的機(jī)械性能和鋸切性能進(jìn)行比較。主要研究結(jié)果如下:(1)重點(diǎn)研究了溫度對鐵族金屬腐蝕金剛石的影響。結(jié)果表明,溫度在腐蝕過程中起關(guān)鍵作用,鐵、鎳、鈷對金剛石單晶腐蝕的初始溫度分別為800°C、700°C和600°C。隨著溫度升高,金剛石單晶的腐蝕程度逐漸加重;當(dāng)溫度相同時(shí),金剛石{100}晶面的腐蝕程度均大于{111}晶面。鐵在金剛石{100}晶面的腐蝕主要沿垂直于晶面方向進(jìn)行,在{111}晶面的腐蝕起源于晶面邊緣并逐漸向中心擴(kuò)展。而鎳和鈷在金剛石表面的腐蝕均以垂直于晶面方向?yàn)橹?在金剛石{100}和{111}晶面上形成形狀分別為倒金字塔和六邊形的腐蝕坑。在試驗(yàn)溫度范圍內(nèi),鈷粉對金剛石單晶腐蝕的均勻性較好,且在金剛石{100}和{111}晶面上的腐蝕率和腐蝕深度均大于鎳粉。(2)系統(tǒng)研究了保溫時(shí)間、金屬粉末與金剛石比例及金屬粉末粒徑等對鐵族金屬腐蝕金剛石的影響。隨著保溫時(shí)間延長,鎳和鈷腐蝕金剛石后形成的腐蝕坑面積和深度逐漸增大,但當(dāng)保溫時(shí)間超過一定值后,延長保溫時(shí)間對金剛石腐蝕影響逐漸減小。減小鈷粉與金剛石的質(zhì)量比,金剛石{100}和{111}晶面的腐蝕率和腐蝕深度明顯降低,同時(shí)金剛石表面腐蝕的均勻性變差。此外,隨著鈷粉粒徑增大,金剛石單晶的腐蝕程度變輕且均勻性變差。(3)探討了鐵族金屬腐蝕金剛石的機(jī)制及腐蝕形貌的形成規(guī)律。金剛石腐蝕過程可描述為:隨著溫度升高,金屬逐漸熔融并開始潤濕金剛石表面;在金屬的催化作用下,金剛石結(jié)構(gòu)碳發(fā)生相變轉(zhuǎn)變成石墨結(jié)構(gòu)碳;金剛石與熔融金屬界面處形成的石墨以濃度差為驅(qū)動力,在金屬中向遠(yuǎn)離界面方向擴(kuò)散。根據(jù)菲克定律對鐵腐蝕金剛石的理論腐蝕深度進(jìn)行計(jì)算,結(jié)果與試驗(yàn)所測P-V值的變化趨勢大體一致。與金剛石臺階狀生長模式相似,鐵族金屬腐蝕金剛石單晶也是通過逐層實(shí)現(xiàn)的。對于金剛石表面形成的腐蝕坑,其底部對應(yīng)于被腐蝕晶面,而其內(nèi)壁則由被腐蝕晶面的相鄰晶面或穩(wěn)定性更高的次級相鄰晶面組成。(4)探索了二水草酸鐵、二水草酸鈷和六水硝酸鈷在不同溫度下對金剛石的腐蝕行為及腐蝕機(jī)理。隨著溫度升高,金剛石單晶的腐蝕程度逐漸加重。特別是以二水草酸鐵作為腐蝕劑時(shí),當(dāng)溫度超過900°C后,金剛石單晶的腐蝕程度急劇加重。二水草酸鈷和六水硝酸鈷均可同時(shí)在金剛石{100}和{111}晶面上形成腐蝕坑,但與金屬鈷粉相比,金剛石單晶腐蝕的均勻性較差,而且在同一個(gè)晶面上腐蝕坑的大小和深度也有較大差別。二水草酸鐵腐蝕金剛石的機(jī)理為金剛石石墨化和氧化,而二水草酸鈷和六水硝酸鈷腐蝕金剛石的主要機(jī)理為金剛石石墨化。(5)分析比較了不同方法處理的金剛石及其與金屬結(jié)合劑復(fù)合燒結(jié)體的機(jī)械性能。與未處理金剛石相比,鍍鈦金剛石的單顆粒抗壓強(qiáng)度和沖擊韌性都較高,與銅基結(jié)合劑復(fù)合制備的燒結(jié)體的硬度、抗彎強(qiáng)度和沖擊強(qiáng)度均無明顯變化,但與鐵基結(jié)合劑復(fù)合制備的燒結(jié)體的抗彎強(qiáng)度和沖擊強(qiáng)度都略有下降。經(jīng)鈷粉腐蝕處理的金剛石的單顆粒抗壓強(qiáng)度和沖擊韌性雖然都略有下降,但與銅基和鐵基結(jié)合劑復(fù)合制備的燒結(jié)體的抗彎強(qiáng)度和沖擊強(qiáng)度均明顯提高。(6)通過鋸切試驗(yàn),對比了不同方法處理的金剛石制備的金屬基鋸片的鋸切性能。與未處理金剛石制備的鋸片相比,鍍鈦金剛石與銅基結(jié)合劑制備的鋸片鋸切試驗(yàn)后工作面上金剛石出刃高度無明顯變化,但50%出刃比例稍有增加,金剛石脫落率略有下降,鋸片鋸切壽命提高15%;與鐵基結(jié)合劑制備的鋸片鋸切試驗(yàn)后工作面上金剛石出刃高度和50%出刃比例均增加,金剛石脫落率明顯降低,鋸片的鋒利度較差,鋸切壽命增加11%。腐蝕處理金剛石與銅基和鐵基結(jié)合劑制備的鋸片鋸切試驗(yàn)后工作面上金剛石出刃高度和50%出刃比例均增加,金剛石脫落率均明顯下降,鋸片自銳性較好,鋸片鋸切壽命分別提高12%和8%。
[Abstract]:Diamond is widely used in the field of hard and brittle materials because of its high hardness, wear resistance and strong chemical inertness. The size of artificial diamond particles is smaller. Usually, the diamond particles are bonded together to prepare a tool with a certain shape, small size and strength. It is difficult to wetting diamond when making diamond tools. Therefore, the main methods are mechanical inlay and weak binding force between them. Most of the diamond is due to premature loss in grinding. In order to improve the holding power of the bond to diamond, the main methods used are mainly to be used at present. The surface of diamond is coated or coated. Aiming at the limitation of these techniques, the paper uses the thermochemistry method to corrode the diamond single crystal with the iron metal and its salt. The influence of the change of the parameters on the corrosion of the diamond single crystal by the iron metal powder is systematically studied, and the corrosion of the iron metal is discussed by the thermodynamic calculation. The main mechanism of diamond single crystal was studied. The corrosion and main mechanism of the iron metal salt at different temperatures on the diamond single crystal were investigated. The diamonds treated by different methods were prepared with the copper base and iron base metal bond respectively. The mechanical properties and sawing properties of the saw blades were compared. The main research results are as follows: (1) focus on the study. The effect of temperature on the corrosion of diamond by iron metal. The results show that temperature plays a key role in the corrosion process. The initial temperature of iron, nickel and cobalt corrosion of diamond single crystal is 800 C, 700 C and 600 degree C., with the increase of temperature, the corrosion degree of diamond single crystal is gradually aggravated; when the temperature is the same, the corrosion degree of the diamond {100} surface is the same. The corrosion of iron on the diamond {100} surface is mainly perpendicular to the direction of the crystal surface, and the corrosion on the {111} crystal surface originates from the edge of the crystal surface and gradually expands to the center, while the corrosion of nickel and cobalt on the diamond surface is perpendicular to the crystal surface, and the shape of the diamond {100} and the {111} crystal surface is the inverted gold character, respectively. Corrosion pits of tower and hexagon. In the range of experimental temperature, cobalt powder has better corrosion to diamond single crystal, and the corrosion rate and corrosion depth on the {100} and {111} surface of diamond are greater than that of nickel powder. (2) the thermal insulation time, the ratio of metal powder to diamond and the particle size of metal powder have been systematically studied. With the prolongation of heat preservation time, the area and depth of the corrosion pit formed by the nickel and cobalt corrosion diamond gradually increased, but the effect of prolonging the heat preservation time on the diamond corrosion gradually decreased. The corrosion rate and the corrosion depth of the diamond {100} and {111} crystal surface and the corrosion depth were obviously reduced. At the same time, the uniformity of the diamond surface corrosion is worse. In addition, with the increase of the particle size of the cobalt powder, the corrosion degree of the diamond single crystal becomes lighter and the uniformity becomes worse. (3) the mechanism of the corrosion of the diamond and the formation law of the corrosion morphology are discussed. The process of diamond corrosion can be described as the gradual melting and beginning of the metal as the temperature rises. The surface of diamond is wetted. Under the catalysis of metal, the phase transition of the diamond structure changes into graphite structure carbon. The graphite formed at the interface between the diamond and the molten metal is driven by the difference of concentration and diffuses in the metal to the direction of the interface. The theoretical corrosion depth of the corroded diamond is calculated according to the law of Fick's law. The results are calculated. Similar to the P-V values measured by the experiment, similar to the diamond step growth pattern, the iron metal corrosion diamond single crystal is also realized by layer by layer. The bottom of the corrosion pit on the diamond surface corresponds to the corroded crystal surface, and its inner wall is adjacent to the corroded crystal surface or the higher stability of the secondary surface. (4) the corrosion behavior and corrosion mechanism of two oxalate, two cobalt oxalate and six cobalt nitrate at different temperatures were explored. The corrosion degree of diamond single crystal increased gradually with the increase of temperature. The corrosion of diamond single crystal when the temperature was more than 900 C. The degree of the cobalt oxalate two and the six water cobalt nitrate can simultaneously form a corrosion pit on the crystal surface of the diamond {100} and {111}, but compared with the metal cobalt powder, the uniformity of the corrosion of the diamond single crystal is poor, and the size and depth of the corrosion pit on the same crystal surface is greatly different. The mechanism of the corrosion of diamond by two oxalate iron is gold. The main mechanism of the corrosion of diamond by cobalt oxalate two and six water cobalt nitrate is diamond graphitization. (5) analysis and comparison of the mechanical properties of the diamond and the composite sintered with the metal bond treated by different methods. Compared with the untreated diamond, the single particle compressive strength and impact toughness of the titanium plated diamond are compared with that of the untreated diamond. The hardness, bending strength and impact strength of the sintered body prepared with the copper base binder were not obviously changed, but the flexural strength and impact strength of the sintered body prepared with the iron base binder decreased slightly. Although the strength and impact toughness of the single particles of the diamond treated by cobalt powder corrosion decreased slightly, but they were slightly reduced. The flexural strength and impact strength of the sinter prepared by the composite of copper base and iron base binder improved obviously. (6) the sawing properties of the metal base saw blades prepared by different methods were compared by sawing test. Compared with the saws prepared from the untreated diamond, the sawing test of the gold plated titanium carbide and copper base binder There is no obvious change in the height of the diamond cutting edge on the post working face, but the ratio of the 50% cutting edge is slightly increased, the drop rate of diamond is slightly decreased and the sawing life of the saw blade is increased by 15%. The diamond cutting edge height and the ratio of 50% out of the blade on the working face are increased after the sawing test of the iron base bond, and the diamond shedding rate is obviously reduced and the blade sharpness is sharp. After the sawing test of 11%. corrosion treatment of diamond and copper base and iron base bond, the diamond cutting edge height and 50% cutting edge ratio increased, the diamond shedding rate decreased obviously, the saw blade's self sharpness was better, the sawing life of saw blade was increased by 12% and 8%., respectively.
【學(xué)位授予單位】：湖南大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：TQ163

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