准干式电火花表面强化TC4强化层显微裂纹研究
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摘要
利用混粉准干电火花表面强化技术对TC4合金进行表面强化,对不同加工条件下的强化层表面裂纹分布情况进行了分析,结果表明:石墨电极正极性强化层裂纹要多于负极性;随峰值电流、脉冲宽度的增加,裂纹数量、长度密度呈增加趋势;强化层裂纹主要为分散性分布的短裂纹,分布于熔融枝状物较细部分、叠加边缘及气孔缺陷处;在峰值电流6. 6～8. 2 A、脉宽80～100μs、负极性加工条件下裂纹萌生数量较少,强化层硬度性能最好。
Surface strengthening of TC4 alloy by using powder-mixed near-dry EDM surface strengthening technology and under different strengthening conditions,the surface crack distribution of strengthened layer was analyzed,The results show that the positive strengthening layer of graphite electrode has more crack than negative electrode. With the increase of peak current and pulse width,the number of cracks and the density of length increase. The strengthened layer crack is mainly a short crack with dispersed distribution,which is distributed in the smaller part of the molten dendritic,the superimposed edge and the stoma defect. Under the condition of peak current 6. 6 ～ 8. 2 A,pulse width 80 ～ 100 μs and negative strengthening,the crack initiation quantity is few and the strengthening layer has the best microhardness.
Surface strengthening of TC4 alloy by using powder-mixed near-dry EDM surface strengthening technology and under different strengthening conditions,the surface crack distribution of strengthened layer was analyzed,The results show that the positive strengthening layer of graphite electrode has more crack than negative electrode. With the increase of peak current and pulse width,the number of cracks and the density of length increase. The strengthened layer crack is mainly a short crack with dispersed distribution,which is distributed in the smaller part of the molten dendritic,the superimposed edge and the stoma defect. Under the condition of peak current 6. 6 ～ 8. 2 A,pulse width 80 ～ 100 μs and negative strengthening,the crack initiation quantity is few and the strengthening layer has the best microhardness.
引文
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[2]Wang H M,Liu Y F. Microstructure and wear resistance of laser clad Ti5Si3/Ni Ti2 intermetallic composite coating on titanium alloy[J].Mater Sci Eng A,2012,338(1–2):126-132.
[3]李敏,王宏伟,蔡兰蓉. TC4钛合金在不同介质下电火花表面强化研究[J].特种铸造及有色金属,2013,33(6):43-48.
[4]潘康,蔡兰蓉,李敏.混粉准干式电火花复合强化TC4钛合金试验研究[J].铸造技术,2015,36(9):2225-2228.
[5]李敏,蔡兰蓉.混粉准干式电火花表面强化TC4钛合金强化层组织与性能[J].特种铸造及有色金属,2017,37(9):1014-1016.
[6]吕战竹,赵福令,杨义勇.混粉电火花表面加工显微裂纹的研究[J].电加工与模具,2007(2):9-12.
[7]钟敏森,刘文今. Nicrsib合金高功率激光送粉熔覆裂纹形成的敏感因素[J].应用激光,2000,20(5):193-198.
[8]汤精明,姜忠宇.电火花表面强化的热应力研究[J].兵器材料科学与工程,2009,32(6):26-30.
[9]Govindan P,Joshi. Analysis of micro-cracks on machined surfaces in dry electrical discharge machining[J]. Journal of Manufacturing Processes,2012,14(3):277-288.
[10]徐明刚,张建华,张勤河,等.超声振动辅助气体介质电火花加工硬质合金表面裂纹特性[J].制造技术与机床,2007(1):41-43.