













摘要"為探究R2O-Al2O3-B2O3-SiO2體系結合劑中各組分含量變化對其性能的影響,通過改變結合劑中Al2O3、B2O3和SiO2的含量,對各組結合劑的耐火度、流動性、熱膨脹系數、抗折強度以及顯微硬度進行測定。結果表明:當Al2O3和SiO2的質量分數分別達到最大25%和65%時,結合劑的耐火度最大,可達815℃;當B2O3的質量分數達到最大30%、Al2O3的質量分數達到最小10%時,結合劑的耐火度最小,為744℃;不同配方結合劑的流動性均為95%~135%;結合劑的熱膨脹系數和抗折強度都會根據n(Al2O3+B2O3)/n(Na2O)的變化表現出不同的變化;各組分對結合劑顯微硬度提高的影響為SiO2gt;B2O3gt;Al2O3。
關鍵詞 陶瓷結合劑組分;三元相圖;熱膨脹系數;力學性能
中圖分類號 TQ171 文獻標志碼 A
文章編號 1006-852X(2024)06-0761-08
DOI 碼 10.13394/j.cnki.jgszz.2023.0126
收稿日期 2023-06-09 修回日期 2024-01-08
陶瓷結合劑磨具是磨料磨具行業的重要組成部分,相較于金屬結合劑磨具與樹脂結合劑磨具,其具有耐熱性好、多孔結構易散熱、易排屑、磨削彈性形變小、磨削精度高、自銳性好等優點[1],被廣泛應用于各行各業。陶瓷結合劑磨具的性能很大程度上取決于陶瓷結合劑的性能,而陶瓷結合劑的性能與其組成成分和制備工藝相關。陶瓷結合劑中,不同的組分具有不同的作用。Al2O3不僅能增強結構鍵合強度,令玻璃網絡結構更加聚合[2],還能促進特定體系結合劑中BaAl2Si2O8和γ-Li-AlSi2O6的形成,改善陶瓷結合劑立方氮化硼(cBN)磨具的耐熱性能和力學性能[3]。B2O3的加入能夠降低
陶瓷結合劑的燒結溫度以及調整熱膨脹系數[4],并且根據陶瓷結合劑中Na2O含量的不同,B2O3在陶瓷結合劑中會表現出不同的性能[5],隨著B2O3含量的升高,陶瓷結合劑中會發生硼反常現象[6]。SiO2作為陶瓷結合劑的主要成分,主要構成陶瓷結合劑的玻璃網絡結構,其含量的變化會直接影響結合劑中Al2O3[7-8]、Li2O[9]、B2O3[10]以及Na2O[11]的性能。堿金屬氧化物[12-15]會向玻璃網絡中提供自由氧,使網絡結構致密度和結合劑耐火度降低、熱膨脹系數升高。Li2O[16]的加入可以降低陶瓷結合劑的燒結溫度,并且能夠析出微晶相。在某些特定的陶瓷結合劑體系中,加入適量合適的添加劑對陶瓷結合劑的性能有很大的提升作用[17-20]。
金剛石是超硬材料行業常用的磨料,但其耐高溫性能較差,因此其所需的結合劑應具有較低的燒結溫度以及合適的流動性和熱膨脹系數。本研究中探究了陶瓷結合劑中Al2O3、B2O3和SiO2的含量對其性能的影響,通過改變3種組分的含量,對比結合劑各性能的變化,以期得到更適合用于金剛石磨具的陶瓷結合劑。
1
實驗
1.1
陶瓷結合劑的制備
根據文獻[21]中R2O-Al2O3-B2O3-SiO2體系結合劑各組分的含量范圍,確認結合劑配方如表1所示。三元相圖中規定三組分質量分數之和為1,因此將配方中Al2O3、B2O3和SiO2的總質量分數設置為100%。為了降低結合劑的耐火度,再添加質量分數為25%的Na2O。其中B2O3用硼酸引入,Na2O用Na2CO3引入。根據總質量達到500g的試樣設計,計算出各原料按照表1中質量分數所需的實際質量并精確稱取,試樣通過球磨機混合均勻后壓制成塊狀,放入高溫熔塊爐中進行1400℃熔融。熔融后將其快速倒入冷水中水淬,水淬后取出玻璃料進行干燥,直至水分烘干,然后進行破碎、球磨,過74μm篩,得到16組結合劑。
1.2
樣品的制備及檢測
將各組結合劑通過質量分數為2.5%的糊精液黏結混合均勻,并在5MPa的壓力下壓制成5mm×6mm×30mm的試樣條,將試樣條在80℃下干燥12h。使用標準耐火錐測量各組結合劑的耐火度,采用平面流淌法測量結合劑的流動性,并對結合劑進行熱膨脹系數的測定。檢測各組結合劑的耐火度后,將每組結合劑以高于結合劑耐火度60℃的溫度為燒結溫度進行燒結,燒結過程中在400℃下保溫0.5h,以除去糊精等揮發性雜質,燒結時間為2h,隨爐冷卻后取出。利用微機控制電子萬能實驗機,采用三點彎曲法,設定跨距為20mm,壓頭以(2±0.5)N/s的速度行進,直到試樣斷裂,測定試樣的抗彎強度,每個試樣測定3次取平均值。利用日本FM-ARS900顯微硬度儀測量結合劑的顯微硬度,并對結合劑進行X射線衍射(XRD)和微觀形貌分析。
2
結果與討論
表1中各組陶瓷結合劑配方中的3種組分在相圖中的位置如圖1所示。圖1中,線a中所有點的SiO2含量相同,線b中所有點的B2O3含量相同,線c中所有點的Al2O3含量相同。選取的結合劑各組分含量的范圍在相圖中僅有一小部分,截取后各配方在相圖中的位置如圖2所示,因此后續分析會截取相圖中有效范圍進行分析。2.1
結合劑的耐火度分析結合劑的耐火度是直接影響磨具燒成溫度的性能指標。各組配方的耐火度結果如表2所示,在三元相圖中的耐火度趨勢如圖3所示,圖3中的結果是3次測量結果的平均值。從表2和圖3可以得出:當SiO2質量分數為60%時,該體系結合劑在B2O3質量分數為30%時具有最小的耐火度744℃,且隨著B2O3質量分數的降低,耐火度逐漸增大;當SiO2質量分數為65%時,該體系結合劑在Al2O3質量分數為25%時具有最大的耐火度815℃,且隨著Al2O3質量分數的降低,耐火度逐漸減小。當Al2O3質量分數為20%時,隨著B2O3質量分數從10%提升至30%,結合劑的耐火度從803℃減小至772℃。當B2O3質量分數為20%時,隨著Al2O3質量分數從10%升至25%,結合劑的耐火度從761℃增大至800℃。
因此可以推斷出,B2O3在陶瓷結合劑中具有降低耐火度的作用,而SiO2和Al2O3在陶瓷結合劑中會使結合劑耐火度升高,且Al2O3對結合劑耐火度的影響要比SiO2的影響大。
2.2
結合劑的流動性分析
結合劑的流動性是反映結合劑在高溫熔融狀態下黏度變化的參數,結合劑的流動性越高,其與磨料的結合性能越好。各組配方的流動性檢測結果如表3所示,在三元相圖中的流動性趨勢如圖4所示。由表3和圖4可以得出:當SiO2含量相同時,結合劑的流動性會隨著B2O3含量的升高而升高;當Al2O3含量相同時,結合劑的流動性會隨著B2O3含量的升高而升高;當B2O3含量相同時,SiO2含量的變化對結合劑流動性的影響不大。因此可以推斷出,B2O3在陶瓷結合劑中具有提高結合劑流動性的作用,而Al2O3則會使陶瓷結合劑的流動性降低。
2.3
結合劑的熱膨脹系數分析
為了使燒結過程中陶瓷結合劑與磨料之間具有更好的把持力,應避免結合劑與磨料界面之間產生熱應力,因此陶瓷結合劑的熱膨脹系數需要與磨料的熱膨脹系數相匹配。各組配方的熱膨脹系數如表4所示,在三元相圖中的熱膨脹系數趨勢如圖5所示。從表4和圖5可以得出:當SiO2含量相同時,結合劑的熱膨脹系數會隨著B2O3含量的升高而升高。當Al2O3質量分數為10%和15%時,結合劑的熱膨脹系數會隨著B2O3含量的升高而升高;當Al2O3質量分數為20%時,結合劑的熱膨脹系數會隨著B2O3含量的升高先降低后升高;當Al2O3質量分數為25%時,結合劑的熱膨脹系數會隨著B2O3含量的升高而降低。當B2O3含量相同時,結合劑的熱膨脹系數會隨著Al2O3含量的升高而升高。
之所以會出現圖5所示的情況,是因為陶瓷結合劑的熱膨脹系數是由各組分的含量及形成的網絡結構決定的。當結合劑中Al2O3+B2O3和Na2O的摩爾比n(Al2O3+B2O3)/n(Na2O)<1時,Al2O3和B2O3會與Na2O中的氧離子結合形成[AlO4]和[BO4],參與到結合劑的網絡結構中,令結合劑的網絡結構致密化,進而降低結合劑的熱膨脹系數;當n(Al2O3+B2O3)/n(Na2O)>1時,Na2O中的氧離子不足,Al2O3和B2O3形成[AlO3]和[BO3]三角體,使網絡結構的致密性降低,導致熱膨脹系數升高。
2.4
結合劑的抗折強度分析
各組配方的抗折強度如表5所示,在三元相圖中的抗折強度趨勢如圖6所示。從表5和圖6可以得出:當SiO2含量相同時,結合劑的抗折強度基本會隨著Al2O3含量的升高而升高。當Al2O3質量分數為10%和15%時,結合劑的抗折強度會隨著B2O3含量的升高而降低;當Al2O3質量分數為20%時,結合劑的抗折強度會隨著B2O3含量的升高先升高后降低;當Al2O3質量分數為25%時,結合劑的抗折強度會隨著B2O3含量的升高而升高。當B2O3含量相同時,結合劑的抗折強度會隨著SiO2含量的升高而升高。其原因是當n(Al2O3+B2O3)/n(Na2O)<1時,結合劑的網絡結構較致密,使得結合劑的抗折強度較高;當n(Al2O3+B2O3)/n(Na2O)>1時,結合劑的網絡結構較為疏松,會產生較多的缺陷等,使得結合劑的抗折強度降低。
2.5
結合劑的顯微硬度分析
各組配方的顯微硬度如表6所示,在三元相圖中的顯微硬度趨勢如圖7所示。結合表6和圖7可以得出:當SiO2質量分數為65%時,結合劑中B2O3質量分數由10%上升至25%,結合劑的顯微硬度上升35MPa;當Al2O3質量分數為15%時,結合劑中SiO2質量分數由15%上升至30%,結合劑的顯微硬度上升60MPa;當B2O3質量分數為20%時,結合劑中SiO2質量分數由55%上升至70%,結合劑的顯微硬度上升93MPa。因此可以推斷出,各組分對結合劑顯微硬度提高的影響為SiO2gt;B2O3gt;Al2O3。在結合劑的玻璃網絡結構中,[SiO4]四面體為主體結構,其對結合劑顯微硬度的影響最大,當SiO2含量較高時,n(Al2O3+B2O3)/n(Na2O)<1,Al2O3和B2O3大多以[AlO4]和[BO4]四面體的形式存在,使得玻璃網絡結構較為致密,結合劑的顯微硬度較大;當SiO2含量較低時,n(Al2O3+B2O3)/n(Na2O)>1,結合劑中除了有[AlO4]和[BO4]四面體,還有一部分[AlO3]和[BO3]三角體存在,導致網絡結構的致密性降低,使結合劑的顯微硬度降低。其中,Al?O鍵的鍵能小于B?O鍵的鍵能,破壞網絡結構中[AlO4]四面體所需的能量小于破壞[BO4]四面體所需的能量,Al?O鍵的鍵長大于B?O鍵,[AlO3]三角體的體積較大,在網絡結構中造成的缺陷更大。因此相對于[BO4]四面體和[BO3]三角體,[AlO4]四面體對網絡結構致密化的影響程度較低,[AlO3]三角體對網絡結構致密化的破壞較大,B2O3對結合劑顯微硬度的影響要大于Al2O3。
2.6
結合劑的微觀形貌分析
圖8為結合劑的微觀形貌圖。對比圖8b、圖8d、圖8f可知:當B2O3含量相同時,結合劑中的氣孔數量和大小相差不大,說明Al2O3和SiO2在結合劑中都起到了使玻璃網絡結構致密化的作用;對比圖8a、圖8d、圖8g可知:當Al2O3含量相同,B2O3含量較高時,[BO3]三角體使玻璃網絡結構疏松,出現較多的氣孔,隨著B2O3含量的降低,玻璃網絡結構趨于致密,但B2O3含量過低則導致結合劑熔融較少,內部空氣無法排除,產生較多的小氣孔;對比圖8c、圖8d、圖8e可知:當SiO2含量相同時,由于Al2O3的相對分子質量較大,隨著Al2O3含量的升高,B2O3物質的量減少較多,但由于Al2O3和B2O3都會生成相應的三角體和四面體,三角體的總數量在減少,結合劑的結構更加趨于致密化。
3
結論
通過調整R2O-Al2O3-B2O3-SiO2體系結合劑中Al2O3、B2O3和SiO2的含量進行燒結,對結合劑的耐火度、流動性、熱膨脹系數、抗折強度、顯微硬度以及微觀形貌進行了測定,將所得數據繪制在三元相圖對應成分區域,依據數據分布特征得出以下結論:
(1)結合劑中SiO2和Al2O3的存在會提高結合劑的耐火度,且Al2O3對結合劑耐火度的影響比SiO2大,但Al2O3會降低結合劑的流動性;B2O3的存在會降低結合劑的耐火度并提高結合劑的流動性。
(2)結合劑的熱膨脹系數和抗折強度都會因Al2O3和B2O3含量的變化而發生不同變化。當結合劑中Al2O3含量較高時,結合劑的熱膨脹系數會隨著B2O3含量的升高先降低再升高,抗折強度會隨著B2O3含量的升高先升高再降低;當結合劑中Al2O3含量較低時,結合劑的熱膨脹系數會隨著B2O3含量的升高而升高,抗折強度會隨著B2O3含量的升高而降低。當SiO2含量相同時,結合劑的熱膨脹系數會隨著B2O3含量升高而升高,抗折強度隨著Al2O3含量的升高而升高;當B2O3含量相同時,結合劑的熱膨脹系數會隨著Al2O3含量的升高而升高,抗折強度隨著B2O3含量的升高而升高。
(3)結合劑中各組分對結合劑顯微硬度提高的影響為SiO2gt;B2O3gt;Al2O3。
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作者簡介
通信作者: 栗正新,男,1964 年生,教授。主要研究方向:磨料磨具、超硬材料及制品,計算機在材料科學中的應用。
E-mail: zhengxin_li@haut.edu.cn
(編輯:王潔)
Effect"of"composition"and"content"on"properties"of"vitrified"bond
CHEN Qi
1 , WANG Chunhua 1 , LI Zhengxin 1 , ZHANG Lin 2 , ZHANG Guowei 2 ,
ZHOU Shaojie
2 , XIA Xuefeng 3 , SHAO Junyong 4
(1. School of Materials Science and Engineering, Henan University of Technology, Zhengzhou 450001, China)
(2. White Dove Abrasives and Grinding Co., Ltd., Zhengzhou 450199, China)
(3. SINOMACH-INT Co., Ltd., Zhengzhou 450018, China)
(4. Chengdu Tool Research Institute Co., Ltd., Chengdu 610500, China)
Abstract
Objectives: Vitrified bonded diamond grinding tools are widely used in the machining industry, but the high-temperature resistance of diamond is poor. Therefore, there are high requirements on sintering temperature, flowability,and thermal expansion coefficient of vitrified bond materials. The influence of the content of Al 2 O 3 , B 2 O 3 , and SiO 2 invitrified bond on its properties is investigated. By changing the content of these three components and comparing thechanges in the properties of the bonds, a more suitable vitrified bond for diamond grinding tools is obtained. Methods:Using a ternary phase diagram, the content of Al 2 O 3 , B 2 O 3 , and SiO 2 in the R 2 O-Al 2 O 3 -B 2 O 3 -SiO 2 bond system is adjus-ted. Sixteen different formulas were designed to prepare 5 mm × 6 mm × 30 mm sample strips under a pressure of 5MPa, and dried at 80 ℃ for 12 hours. The refractoriness of each group of bonds was measured using a standard refract-ory cone, the flowability of the bonds was measured using the plane flow method, and the thermal expansion coefficientof the bonds was determined. According to the refractoriness data determined by each formula, sintering was carried outat a temperature 60 ℃ higher than the refractoriness of the bond. A microcomputer-controlled electronic universal test- ing machine was used to determine the flexural strength of the bond using the three-point bending method. The micro-hardness of the bond was measured using a microhardness tester, and the microstructure of the bond was analyzed. Res-ults:"From the analysis of the measured performance data, it can be concluded that: (1) B 2 O 3 has the effect of reducingthe refractoriness in vitrified bonds, while SiO 2 and Al 2 O 3 increase the refractoriness of the bonds. Al 2 O 3 has a greaterimpact on the refractoriness of the bonds than SiO 2 . (2) B 2 O 3 has the effect of improving the flowability of bonds, whileAl 2 O 3 reduces the flowability of bonds. The thermal expansion coefficient and the flexural strength of the bond will varydepending on the content of Al 2 O 3 and B 2 O 3 . When the Al 2 O 3 content in the bond is high, the thermal expansion coeffi-cient of the bond will first decrease and then increase with the increase of B 2 O 3 content, and the flexural strength willfirst increase and then decrease with the increase of B 2 O 3 content. When the Al 2 O 3 content in the bond is low, thethermal expansion coefficient of the bond will increase with the increase of B 2 O 3 content, and the flexural strength willdecrease with the increase of B 2 O 3 content. When the SiO 2 content is fixed, the thermal expansion coefficient of thebond will increase with the increase of B 2 O 3 content, and the flexural strength will increase with the increase of Al 2 O 3content. When the B 2 O 3 content is fixed, the thermal expansion coefficient of the bond will increase with the increase ofAl 2 O 3 content, and the flexural strength will increase with the increase of B 2 O 3 content. The influence of each compon-ent in the bond on the microhardness change of the bond is SiO 2 gt;B 2 O 3 gt;Al 2 O 3 . When the molar ratio of Al 2 O 3 +B 2 O 3 toNa 2 O in the bond is less than 1, Al 2 O 3 and B 2 O 3 will combine with oxygen ions in Na 2 O to form [AlO 4 ] and [BO 4 ],which participate in the network structure of the bond and densify it. Breaking the dense network structure requireshigher energy. Therefore, densification of the network structure in the bond can reduce its thermal expansion coefficientand improve its flexural strength and microhardness. When n(Al 2 O 3 +B 2 O 3 )/n(Na 2 O)gt;1, the oxygen ions in Na 2 O are in-sufficient, and Al 2 O 3 and B 2 O 3 form [AlO 3 ] and [BO 3 ] triangles, reducing the density of the network structure. The fluffystructure makes the network structure more sensitive to energy, increasing the thermal expansion coefficient of the bondand reducing its flexural strength and microhardness. Conclusions: A ternary phase diagram based on the content ofAl 2 O 3 , B 2 O 3 , and SiO 2 in the R 2 O-Al 2 O 3 -B 2 O 3 -SiO 2 system bond can intuitively reflect the synergistic effect of the threecomponents during sintering. The three components will exhibit different effects in bonds with different contents, andtheir impact on the performance of the bond will also be different. When designing the formula for vitrified bonds, it isnecessary to consider the roles of different components in the bond and their interactions with other components.
Key"words
vitrified bond components;ternary phase diagram;thermal expansion coefficient;mechanical property