火箭推进

针对再生冷却推力室等零件在服役过程中经受循环热冲击,容易发生热疲劳失效等问题,采用机械球磨混粉和激光定向能量沉积相结合的方法,在Stellite 6合金中添加铝和镍元素,制备了新型钴基合金。在室温至600 ℃进行自约束热疲劳测试,并采用扫描电子显微镜、X射线衍射和激光共聚焦显微镜等多种方式系统表征了测试前后钴基合金的显微组织演变和裂纹萌生及扩展过程。结果表明:与商用Stellite 6钴基合金相比,铝和镍元素的添加抑制了沉积态钴基合金中ε-Co的出现,并且在热疲劳过程中也限制了γ-Co向ε-Co的转变。3Al合金和3Al5Ni合金热疲劳裂纹出现的临界循环次数分别提高了250次和550次,裂纹扩展速率降低了7.5%和12.25%。新型钴基合金拥有更高的层错能,组成相更稳定,热疲劳过程中γ/*相界面更少,减少了热疲劳裂纹萌生和扩展,从而大幅提升抗热疲劳性能。

The regeneration cooling thrust chamber is prone to thermal fatigue failure owing to cyclic thermal shock during the service process. To solve the problem, novel cobalt-based alloys were prepared by adding Al and Ni into Stellite 6 alloy through mechanical ball milling and laser directed energy deposition. The test was carried out on the self-confined thermal fatigue equipment from room temperature to 600 ℃. The evolutions of microstructures and cracks during the thermal fatigue test were systematically characterized through SEM, XRD and LSM. The results indicated that the additions of Al and Ni inhibit the formation of ε-Co in the deposited cobalt-based alloy compared with Stellite 6 alloy, meanwhile, the transformation of γ-Co to ε-Co is also restricted during the thermal fatigue test. The critical cycles of thermal fatigue crack of 3Al alloy and 3Al5Ni alloy increased by 250 and 550 cycles respectively. Moreover, the crack propagation rates of the alloys were reduced by 7.5% and 12.25%. Novelcobalt-based alloys exhibit higher stacking fault energy which could stabilize phases. It also decreases the amounts of γ/ε phase boundaries that easily occur thermal fatigue cracks, which is beneficial for improving thermal fatigue resistance.

引言
1 试验方法
2 结果与讨论
3 结论

$表1 钴基合金粉末与基板各元素的质量分数<br/>Tab.1 Mass fraction for different element of cobalt-based powder and substrate 单位:%$

表1 钴基合金粉末与基板各元素的质量分数
Tab.1 Mass fraction for different element of cobalt-based powder and substrate 单位:%

图1 激光定向能量沉积设备、Stellite 6粉末及热疲劳试样<br/>Fig.1 Laser directed energy deposition equipment, Stellite 6 powder and thermal fatigue sample

图1 激光定向能量沉积设备、Stellite 6粉末及热疲劳试样
Fig.1 Laser directed energy deposition equipment, Stellite 6 powder and thermal fatigue sample

图2 热疲劳试验装置及温升曲线<br/>Fig.2 Thermal fatigue equipment and relation curve of induction heating time versus temperature

图2 热疲劳试验装置及温升曲线
Fig.2 Thermal fatigue equipment and relation curve of induction heating time versus temperature

图3 沉积态钴基合金显微组织<br/>Fig.3 Microstructures of deposited cobalt-based alloys

图3 沉积态钴基合金显微组织
Fig.3 Microstructures of deposited cobalt-based alloys

图4 沉积态钴基合金等轴晶区显微组织<br/>Fig.4 Microstructures of equiaxed dendrite grain area of deposited cobalt-based alloys

图4 沉积态钴基合金等轴晶区显微组织
Fig.4 Microstructures of equiaxed dendrite grain area of deposited cobalt-based alloys

$表2 图4中测试点的元素质量分数<br/>Tab.2 Mass fraction of different element of test points in Fig.4 单位:%$

表2 图4中测试点的元素质量分数
Tab.2 Mass fraction of different element of test points in Fig.4 单位:%

$图5 沉积态钴基合金XRD衍射图谱<br/>Fig.5 XRD diffractions of deposited cobalt-based alloys$

图5 沉积态钴基合金XRD衍射图谱
Fig.5 XRD diffractions of deposited cobalt-based alloys

图6 热疲劳裂纹萌生和扩展统计图<br/>Fig.6 Statistical graph of thermal fatigue cracks initiation and propagation

图6 热疲劳裂纹萌生和扩展统计图
Fig.6 Statistical graph of thermal fatigue cracks initiation and propagation

图7 Stellite 6合金热疲劳裂纹形貌<br/>Fig.7 Thermal fatigue cracks morphologies of Stellite 6 alloy

图7 Stellite 6合金热疲劳裂纹形貌
Fig.7 Thermal fatigue cracks morphologies of Stellite 6 alloy

图8 3Al合金热疲劳裂纹形貌<br/>Fig.8 Thermal fatigue cracks morphologies of 3Al alloy

图8 3Al合金热疲劳裂纹形貌
Fig.8 Thermal fatigue cracks morphologies of 3Al alloy

图9 3Al5Ni合金热疲劳裂纹形貌<br/>Fig.9 Thermal fatigue cracks morphologies of 3Al5Ni alloy

图9 3Al5Ni合金热疲劳裂纹形貌
Fig.9 Thermal fatigue cracks morphologies of 3Al5Ni alloy

图10 沉积态钴基合金热疲劳裂纹EBSD分析结果<br/>Fig.10 EBSD analysis for thermal fatigue cracks of deposited cobalt-based alloys

图10 沉积态钴基合金热疲劳裂纹EBSD分析结果
Fig.10 EBSD analysis for thermal fatigue cracks of deposited cobalt-based alloys

图11 沉积态钴基合金热疲劳测试后组成相统计图<br/>Fig.11 Statistical graph of phase compositions of deposited cobalt-based alloys after thermal fatigue test

图11 沉积态钴基合金热疲劳测试后组成相统计图
Fig.11 Statistical graph of phase compositions of deposited cobalt-based alloys after thermal fatigue test

表3 钴基合金参数<br/>Tab.3 Parameters of cobalt-based alloys

表3 钴基合金参数
Tab.3 Parameters of cobalt-based alloys

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备注

引言

1 试验方法

2 结果与讨论

3 结论

期刊信息