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在K418叶片的修复再制造体系中,因其基体K418与熔覆材料Inconel718具有相近的成分组成,同属于镍基高温合金的范畴。故选择粒度为150μm的Inconel718高温合金粉末,试验中基材选用8mm厚的K418锻造板,试验前先将熔覆材料Inconel718合金置于真空干燥箱内在150℃以下干燥2h,试验前使用砂纸对基材进行打磨,并用丙酮清洗,以去除表面铁锈及氧化膜,熔覆材料Inconel718的主要成分如表 1所示。
Table 1. Chemical constituents (mass fraction) of K418 and Inconel718 superalloys
element Ni Cr Mo Al Ti C Nb Zr K418 balance 0.1150~0.1350 0.0380~0.0480 0.0550~0.0640 0.005~0.01 0.0008~0.0016 — 0.0006~0.0015 Inconel718 balance 0.1700~0.2100 0.0280~0.0330 0.0030~0.7000 0.0075~0.0115 0.0002~0.0006 0.0500~0.0550 试验中采用YLS-4000光纤激光再制造系统,采用同轴送粉方式,熔覆过程对熔池施加氩气保护, 试验设备原理及现场图如图 1所示。样本分析试验用单道激光熔覆工艺参量如表 2所示。各组参量中激光光斑离焦量为3mm,脉宽为10ms,占空比为1:1,在每个熔覆单道中部经线切割取样、镶样、打磨并抛光,利用5g FeCl3+20mL HCl+20mL C2H5OH的腐蚀液的配方腐蚀10s~15s,利用MR5000型倒置金相显微镜观察金相组织,采用HVS-1000B型显微硬度测定仪进行硬度测试,采用Sigma500型场发射扫描电子显微镜(field emission scanning electron microscope,FE-SEM)及配制的OXFORD电子能谱仪(energy dispersive spectroscopy,EDS)进行物相分析。
Figure 1. Equipment schematic diagram and scene diagram of pulsed laser remanufacturing a—schematic diagram b—scene diagram
Table 2. Process parameters of laser remanufacture
No. power
P/kWscanning speed
vs/(mm·min-1)carrier gas flow
vg/(L·h-1)feeding rate speed
v/(g·min-1)1# 1.5 360 180 35.0 2# 2.0 360 180 35.0 3# 2.5 480 180 37.5 -
图 2为K418涡轮叶片激光再制造成形前及成形后待加工件的形貌图。因为激光再制造后的叶片必须通过铣削或磨削才能达到可使用状态,所以在其修复区保留了足够的打磨余量。由成形后待加工图观察可知,采用Inconel718激光再制造K418涡轮叶片的修复成形较好,工艺上采用了防塌陷设计避免了叶片边缘易塌陷的问题,该试验及相关工艺参量为K418涡轮叶片的激光再制造修复成形提供一定的借鉴与分析。
K418合金叶片激光再制造Inconel718覆层匹配与强化
Matching and strengthening between Inconel718 cladding and K418 alloy blades by laser remanufacturing
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摘要: 为了解决K418合金叶片再制造熔覆层易开裂、结合界面处力学性能较差等难题,采用具有输入可调控、热输入可控制以及降低熔池及热影响区温度等优势的脉冲激光,得出在工艺参量为激光功率2.5kW、送粉速率37.5g/min、扫描速率8mm/s,载气气流3L/min下,K418基体与Inconel718熔覆层之间能够形成良好的冶金结合。结果表明,熔覆层显微组织依次由界面处平面晶、底部胞状晶、中部树枝晶及顶部等轴晶组成;经过对比优化下的工艺参量,获得了成形质量良好且无明显裂纹、气孔等缺陷的Inconel718熔覆层;通过基体与覆层的硬度测试,覆层整体硬度值在300HV左右且分布较为均匀,基体平均硬度在400HV以上、结合界面处硬度值为460.46HV,相对于基体提升了12%;物相形分析表明,Inconel718熔覆层与基体K418性能匹配较好,激光再制造凝固成形时经历了L→γ→(γ+MC)→(γ+laves)的凝固过程,脉冲激光的热输入对基体K418合金热影响区完成了γ′相的固溶再析出过程,界面处沿晶界析出少量的二次析出相laves相和MC相对熔覆层及界面处晶界起到钉扎晶界、阻碍滑移的强化作用。试验相关工艺及参量为K418叶片激光再制造提供了借鉴和分析。
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关键词:
- 激光技术 /
- 激光再制造 /
- Inconel718 /
- 叶片 /
- 性能匹配
Abstract: The cladding layer of K418 alloy blade after remanufacturation was easy to crack and the mechanical properties of bonding interface were poor. In order to solve these problems, the pulsed laser with the advantages of adjustable input, controllable heat input and lower temperature of molten pool and heat affected zone was used. Good metallurgical bonding was formed between K418 matrix and Inconel718 cladding layer under the conditions of laser power 2.5kW, powder feeding rate 37.5g/min, scanning rate 8mm/s and carrier gas flow 3L/min. The results show that the microstructure of the cladding layer is composed of plane crystal at the interface, cell crystal at the bottom, dendrite in the middle and equiaxed crystal at the top. Under the optimized process parameters, Inconel718 cladding layer with good forming quality and without obvious cracks and pore defects is obtained. After the test of the hardness of the matrix and the coating, overall hardness of the coating is about 300HV and the distribution is uniform. Average hardness of the matrix is above 400HV, and the hardness of the bonding interface is 460.46HV, which is 12% higher than that of the matrix. Phase analysis shows that, the properties of Inconel718 cladding layer and matrix K418 match well. The solidification process of laser remanufacturing is L→γ→(γ+MC)→(γ+laves). Solid solution and precipitation of γ′ phase in heat affected zone of matrix K418 alloy are completed by heat input of the pulsed laser. A small amount of secondary precipitates is precipitated along the grain boundary at the interface. Laves phase and MC phase can pin the grain boundary and hinder the slip of the cladding layer and the grain boundary at the interface. The related process and parameters can be used for reference and analysis of K418 blade laser remanufacturing.-
Key words:
- laser technique /
- laser remanufacturing /
- Inconel718 /
- blade /
- performance matching
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Figure 8. EDS of Fig. 7a a—A point b—B point c—C point d—D point
Table 1. Chemical constituents (mass fraction) of K418 and Inconel718 superalloys
element Ni Cr Mo Al Ti C Nb Zr K418 balance 0.1150~0.1350 0.0380~0.0480 0.0550~0.0640 0.005~0.01 0.0008~0.0016 — 0.0006~0.0015 Inconel718 balance 0.1700~0.2100 0.0280~0.0330 0.0030~0.7000 0.0075~0.0115 0.0002~0.0006 0.0500~0.0550 Table 2. Process parameters of laser remanufacture
No. power
P/kWscanning speed
vs/(mm·min-1)carrier gas flow
vg/(L·h-1)feeding rate speed
v/(g·min-1)1# 1.5 360 180 35.0 2# 2.0 360 180 35.0 3# 2.5 480 180 37.5 -
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