铁基粉末流动温压工艺中热脱脂动力学分析

杨义; 倪东惠

doi:10.19591/j.cnki.cn11-1974/tf.2018.04.010

铁基粉末流动温压工艺中热脱脂动力学分析

doi: 10.19591/j.cnki.cn11-1974/tf.2018.04.010

杨义^1, ,,
倪东惠²

1.
湖北工程学院机械工程学院, 孝感 432000
2.
华南理工大学机械与汽车工程学院, 广州 510640

基金项目:

湖北省教育厅科学研究项目资助项目 B2017165

详细信息

通讯作者:
杨义, E-mail: ygyi2009@163.com

中图分类号: TF124.1
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- 被引次数: 0
出版历程
- 收稿日期: 2018-01-22
- 刊出日期: 2018-08-27

Analysis on thermal debinding kinetics of iron-based powders by warm flow compaction

YANG Yi^{1
, ,},
NI Dong-hui²

1.
School of Mechanical Engineering, Hubei Engineering University, Xiaogan 432000, China
2.
School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640, China

More Information

Corresponding author: YANG Yi, E-mail: ygyi2009@163.com

摘要

摘要: 采用流动温压工艺，以铁基粉末为原料、石蜡基聚合物为黏结剂成功制备出十字坯试样；在不同热脱脂速率下脱除聚合物黏结剂，利用热重分析（thermogravimetric analysis，TGA）法研究黏结剂在N₂气氛下的热脱脂行为，采用微分法计算脱脂过程动力学相关参数，改进脱脂工艺；借助优化后的脱脂工艺对压坯进行脱脂，并在1300℃烧结获得烧结坯，对烧结坯的烧结收缩率、密度分布、微观组织进行研究。结果表明：聚合物黏结剂的脱除共有2个阶段，激活能为31.3~72.7 kJ·mol^-1，指前因子为0.96×106~1.14×1010 min^-1；脱脂第1阶段的激活能整体上均低于第2阶段的激活能，说明脱脂第1阶段中的低分子组元更易脱除，保证脱脂质量的关键因素是控制第1阶段的升温速率。
- 流动温压 /
- 铁基粉末 /
- 热脱脂 /
- 脱脂速率 /
- 动力学
Abstract: Cross-shaped parts were prepared by flow warm compaction using iron-based powders as raw material and paraffin wax-based polymer as binder, the polymer binder was removed at different debinding rates. The thermogravimetric analysis (TGA) was used to study the thermal debinding behavior of binder under N₂ atmosphere, and the kinetic parameters were investigated by derivative thermogravimetric method. The parts prepared by the optimized debinding parameters were sintered at 1300℃, and the shrinkage, density distribution, and microstructures of the sintered parts were studied. Results show that, the thermal debinding processes can be divided into two stages, the activation energy and pre-exponential factor are ranging from 31.3 to 72.7 kJ·mol^-1 and 0.96×106 to 1.14×1010 min^-1, respectively. The activation energy of stage 1 is lower than that of stage 2, which means that it is easier to remove low molecular polymer binder in stage 1. The key factor of debinding quality is to control the heating rate of stage 1.
- warm flow compaction /
- iron-based powders /
- thermal debinding /
- debinding rate /
- kinetic

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图 1 热重–微商热重分析曲线：（a）纯黏结剂；（b）含质量分数6%黏结剂的生坯

Figure 1. TG–DTG curves: (a) binder; (b) green compaction with 6% binder by mass

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图 2 不同升温速率下生坯的微商热重曲线

Figure 2. DTG curves of green compaction at different heating rates

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图 3 Arrhenius方程ln[k(T)]与T^-1关系：（a）第1阶段470~660 ℃；（b）第2阶段660~760 ℃

Figure 3. Plot of ln[k(T)] and T^-1: (a) 470~660 ℃ in stage 1; (b) 660~760 ℃ in stage 2

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图 4 脱脂缺陷：（a）裂纹；（b）鼓泡

Figure 4. Defects induced by debinding: (a) cracks; (b) blisters

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图 5 优化后热脱脂工艺

Figure 5. Optimized debinding process

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图 6 烧结坯不同部位金相组织：（a）轴向上端；（b）横向左端

Figure 6. Microstructures of sintered parts at different location: (a) axial upper-side; (b) lateral left-side

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图 7 烧结坯的密度分布（单位：g·cm^-3）

Figure 7. Density distribution of sintered parts (unit in g·cm^-3)

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表 1 实验用金属粉末的成分与粒度

Table 1. Composition and particle sizes of the raw powders

粉末	粒度/μm	质量分数/%
水雾化铁粉	≤147	78.5
羟基铁粉	5	20.0
还原钼粉	≤75	0.5
石墨粉	≤75	1.0

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表 2 黏结剂组元热解温度和成分

Table 2. Thermal characteristic and composition of binder components

组元	熔点/ ℃	热分解温度/ ℃	质量分数/ %
聚酰胺（PA）	170.6	316.6~500.5	65.0
聚乙烯蜡（PE）	113.1	192.3~480.9	17.5
普通石蜡（PW）	64.7	180.1~307.0	17.5

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表 3 生坯脱脂过程动力学参数

Table 3. Kinetic parameters of green compact with diffeent heating rates

热解阶段	升温速率，β/(℃·min^-1)	激活能，E_a/(kJ·mol^-1)	指前因子，A / min^-1	拟合系数，r²
第1阶段（低温阶段）	2	44.3	5.82×10⁶	0.9954
	5	31.3	0.96×10⁶	0.9970
	8	34.8	3.23×10⁶	0.9916
	11	31.6	1.94×10⁶	0.9954
第2阶段（高温阶段）	5	56.3	1.45×10⁸	0.9914
	8	70.2	4.65×10⁹	0.9937
	11	72.7	1.14×10¹⁰	0.9938

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表 4 生坯密度、烧结坯密度和烧结收缩率

Table 4. Green density, sintered part density, and sintered part shrinkages

生坯密度/ (g·cm^-3)	烧结密度/ (g·cm^-3)	烧结收缩率/%
生坯密度/ (g·cm^-3)	烧结密度/ (g·cm^-3)	轴向方向	轴向直径	横向方向	横向直径
5.971	6.720	-5.83	-0.27	-6.10	-0.31

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