纯相低氧纳米WC-Co复合粉的制备
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摘要
以紫钨、四氧化三钴、炭黑为原料,在高真空度条件下利用原位反应合成技术制备出物相纯净、平均粒径约为80 nm的WC-Co复合粉。研究了制备工艺参数对纳米复合粉相组成、粒径、氧含量及最终烧结硬质合金块体材料组织性能的影响。结果表明,纳米复合粉中氧含量较高时,会导致后续烧结过程中发生脱碳反应,使烧结制备的块体材料致密度和力学性能明显下降。将纳米复合粉在800℃下真空热处理2.5 h可有效降低粉末中的氧含量,同时热处理后的粉末颗粒无明显长大,平均粒径为85 nm。向复合粉中加入1.1%TiC与0.9%VC进行SPS烧结,烧结块体平均晶粒尺寸为105 nm,且尺寸分布均匀,致密度达99%以上,硬度(HV30)为21 450 MPa,断裂韧性达到9.81 MPa·m~(1/2)。
Using tungsten oxide,cobalt oxide and carbon black as the raw materials,the nano WC-Co composite powders with pure phases and a mean particle size of about 80 nm were synthesized by the technique of in-situ reactions under high vacuum.The effects of preparation conditions on the phase constitution,the particle size and the oxygen content of the composite powder as well as on the microstructure and mechanical properties of the sintered bulk were investigated.Results indicate that the decarburization reaction occurs in the sintering process when the oxygen content of the composite powder is higher,leading to a decrease in density and mechanical properties of the sintered bulk.The oxygen content of the powder could be significantly reduced through a heat-treatment at 800oC for 2.5 h.After that,the powders still have a mean particle size of 85 nm.The SPS sintering was performed using the heat-treated composite powder in which 1.1%TiC and 0.9%VC were added as grain growth inhibitors.The sintered WC-Co bulk has a density higher than 99% and a homogeneous grain size distribution.The mean grain size is 105 nm.Moreover,the hardness(HV30) and fracture toughness of the bulk reach 21 450 MPa and 9.81 MPa·m~(1/2),respectively,superior to that prepared with the unheated powders.
Using tungsten oxide,cobalt oxide and carbon black as the raw materials,the nano WC-Co composite powders with pure phases and a mean particle size of about 80 nm were synthesized by the technique of in-situ reactions under high vacuum.The effects of preparation conditions on the phase constitution,the particle size and the oxygen content of the composite powder as well as on the microstructure and mechanical properties of the sintered bulk were investigated.Results indicate that the decarburization reaction occurs in the sintering process when the oxygen content of the composite powder is higher,leading to a decrease in density and mechanical properties of the sintered bulk.The oxygen content of the powder could be significantly reduced through a heat-treatment at 800oC for 2.5 h.After that,the powders still have a mean particle size of 85 nm.The SPS sintering was performed using the heat-treated composite powder in which 1.1%TiC and 0.9%VC were added as grain growth inhibitors.The sintered WC-Co bulk has a density higher than 99% and a homogeneous grain size distribution.The mean grain size is 105 nm.Moreover,the hardness(HV30) and fracture toughness of the bulk reach 21 450 MPa and 9.81 MPa·m~(1/2),respectively,superior to that prepared with the unheated powders.
引文
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[4]Wei Chongbin(魏崇斌),Song Xiaoyan(宋晓艳),Wang Shequan(王社权)et al.Cemented Carbide(硬质合金)[J],2015,32(2):119
[5]Zhang Wuzhuang(张武装),Gao Haiyan(高海燕),Huang Boyun(黄伯云).Rare Metal Materials and Engineering(稀有金属材料与工程)[J],2007,36(7):1253
[6]Ban Z G,Shaw L L.Acta Materialia[J],2001,49(15):2933
[7]Shaw L L,Luo H,Zhong Y.Mater Sci Eng A[J],2012,537:39
[8]Ouyang Yafei(欧阳亚非),Wu Yinfang(邬荫芳),Peng Zehui(彭泽辉).China Tungsten Industry(中国钨业)[J],1999,14(5-6):210
[9]Mc Candlish L E,Kear B H,Bhatia S J.US Patent,5352269[P],1994
[10]Jin Y Z,Huang B,Liu C H et al.International Journal of Refractory Metals and Hard Materials[J],2013,41:169
[11]Gavrilov N M,Pa?ti I A,Krsti?J et al.Ceranics International[J],2013,39(8):8761
[12]Adorjan C,Bock A,Myllymaki S et al.International Journal of Refractory Metals and Hard Materials[J],2008,26:569
[13]Zawrah M F.Ceranics International[J],2007,33(2):155
[14]Sun S K,Kan Y M,Zhang G J et al.J Am Ceram Soc[J],2010,93(11):3565
[15]Chen D L,Wen H J,Zhai H T et al.J Am Ceram Soc[J],2010,93(12):3997
[16]Liu W B,Song X Y,Zhang J X et al.J Alloy Compd[J],2008,458(1-2):366
[17]Liu W B,Song X Y,Zhang J X et al.Mater Chem Phys[J],2008,109(2-3):235
[18]Gao Yang(高杨),Song Xiaoyan(宋晓艳),Liu Xuemei(刘雪梅)et al.Rare Metal Materials and Engineering(稀有金属材料与工程)[J],2014,43(5):1224
[19]Liu W B,Song X Y,Zhang J X et al.International Journal of Refractory Metals and Hard Materials[J],2009,27(1):115
[20]Sun L,Yang T E,Jia C C et al.Rare Metals[J],2011,30(1):63
[21]Ban Z G,Shaw L L.Journal of Materials Science[J],2002,37(16):3397
[22]Gao L,Kear B H.Nanostructured Materials[J],1997,9:205
[23]Ma J,Zhu S G.International Journal of Refractory Metals and Hard Materials[J],2010,28(5):623
[24]Singh H,Pandey O P.Ceramics International[J],2013,39(1):785
[25]Sautereau J,Mocellin A.Journal of Materials Science[J],1974,9(5):761
[26]Kelly J P,Graeve O A.Acta Materialia[J],2015,84:472
[27]Clark B M,Kelly J P,Graeve O A.Mater Res Soc Proc[J],2012,1485:9