Rheological property and solvent debinding behavior of microcrystalline wax based feedstocks for injection molding
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摘要: 以微晶蜡为粘结剂主要组元，与WC–10Co（YG10）粉末密炼混合，得到注射成形喂料。通过线性拟合计算出喂料的非牛顿指数、粘流活化能和综合流变学因子，考察不同温度与剪切速率下喂料的流变性能。对成形坯体在不同温度下于不同脱脂溶剂中的失重进行分析，考察坯体的溶剂脱脂动力学行为。结果表明，微晶蜡基喂料呈现假塑性流体的剪切稀化特征，对剪切速率和温度的敏感性较为稳定，综合流变性能良好。可溶性粘结剂组元的脱除主要发生在脱脂前期，由扩散所控制，且随着坯体厚度和体积的减小及脱脂温度的升高，扩散系数增大。Abstract: Microcrystalline wax was mixed with the WC–10Co (YG10) powders to obtain the injection molding feedstocks as the main component of the binders. The non-Newtonian index, viscous flow activation energy, and synthetic rheological factor of the feedstocks were calculated by linear fitting, and the rheological properties of the feedstocks at the different temperatures and shear rates were investigated. The kinetic behavior of the solvent debinding for green bodies was investigated by analyzing the weight loss of the green bodies in the different debinding solvents at the different temperatures. The results show that, the microcrystalline wax based feedstocks exhibit the shear thinning characteristics of pseudoplastic fluid. The feedstocks have the stable sensitivity to the shear rate and temperature fluctuation, and show the good comprehensive rheological properties. The removal of soluble binder components mainly occurs in the pre-solvent debinding stage, which is controlled by diffusion, and the diffusion coefficient increases with the decrease of the thickness and volume of the green body and the increase of the debinding temperature.
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图 1 喂料在不同温度与剪切速率下的粘度
Figure 1. Viscosity of the feedstock at different temperatures and shear rates
图 2 喂料在不同温度下logη与logγ的关系
Figure 2. Relationship between logη and logγ of the feedstock at different temperatures
图 3 喂料logη与1/T的关系（剪切速率为400 s‒1）
Figure 3. Relationship between logη and 1/T of the feedstocks with the shear rate of 400 s‒1
图 5 不同温度下坯体在正庚烷中的脱脂率
Figure 5. Debinding rate of the green parts in n-heptane at different temperatures
图 7 坯体A不同脱脂条件下ln(‒lnF)与1/T的关系：（a）三氯乙烯；（b）正庚烷；（c）煤油
Figure 7. Relationship between ln(‒lnF) and 1/T under the different debinding conditions of green part A: (a) trichloroethylene; (b) n-heptane; (c) kerosene
图 8 坯体B不同脱脂条件下ln(‒lnF)与1/T的关系：（a）三氯乙烯；（b）正庚烷；（c）煤油
Figure 8. Relationship between ln(‒lnF) and 1/T under the different debinding conditions of green part B: (a) trichloroethylene; (b) n-heptane; (c) kerosene
图 9 正庚烷中不同脱脂时间下坯体表面和断面的显微形貌：（a）生坯表面；（b）1 h表面；（c）3 h表面；（d）5 h表面；（e）生坯断面；（f）1 h断面；（g）3 h断面；（h）5 h断面
Figure 9. Surface and section SEM images of the green parts in the different debinding times: (a) surface, 0 h; (b) surface, 1 h; (c) surface, 3 h; (d) surface, 5 h; (e) section, 0 h; (f) section, 1 h (g) section, 3 h; (h) section, 5 h
表 1 不同溶剂与温度的动力学参数
Table 1. Kinetic parameters in the different solvents at the different temperatures
溶剂 30 ℃扩散系数 / (×10‒3 mm2·s‒1) 35 ℃扩散系数 / (×10‒3 mm2·s‒1) 40 ℃扩散系数 / (×10‒3 mm2·s‒1) A B A B A B 三氯乙烯 3.81 9.70 4.22 11.26 4.66 13.01 正庚烷 2.45 9.27 3.01 10.89 3.68 12.74 煤油 1.73 6.96 1.98 7.78 2.26 8.66 
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