喷丸辅助对冷喷涂Ni-Al含能结构涂层组织及性能的影响

Influence of In-situ Shot Peening on Microstructure and Properties of Cold-sprayed Ni-Al Energetic Structural Coating

目的调控冷喷涂Ni-Al含能结构涂层的微观结构,增加涂层中组元间的接触面积,提高涂层反应速度。方法在Ni、Al混合粉末中引入铸钢弹丸,研究喷丸辅助对冷喷涂Ni-Al涂层微观组织、力学性能和反应特征的影响。采用扫描电镜(SEM)结合定量金相方法,表征Ni-Al涂层微观形貌和Ni、Al组元的接触面积。通过万能材料试验机及分离式霍普金斯压杆(SHPB)测试Ni-Al涂层的压缩力学性能。采用差示扫描量热分析法(DSC)分析Ni-Al涂层的反应温度及放热量。通过高速摄影分析Ni-Al涂层的自蔓延反应过程和燃烧速度。结果喷丸辅助冷喷涂所制备的Ni-Al涂层整体致密、无宏观裂纹。弹丸冲击提高了涂层中Ni颗粒的变形程度和Ni、Al组元间的接触面积,对涂层密度和Ni、Al活性组元含量无明显影响。喷丸辅助冷喷涂Ni-Al在准静态和动态条件下的抗压强度分别为210~250 MPa及310~335 MPa。引入弹丸提高了冷喷涂Ni-Al涂层的反应活性,反应起始温度下降至422℃,并显著提高了冷喷涂Ni-Al含能结构涂层的自蔓延燃烧速度。当钢丸添加量为77%时,涂层燃烧速度达到416 mm/s,提高近5倍。结论喷丸辅助冷喷涂工艺可在保证涂层力学性能的同时,提高Ni-Al含能结构涂层的反应活性,并显著提高自蔓延燃烧速度,弹丸含量对涂层成分影响不大。

The work aims to adjust the microstructure of cold-sprayed Ni-Al coating,enhance the contact area of coating elements and improve the reaction velocity of coating.The cast steel pills were added into the mixed powder of Ni and Al to study the influence of in-situ shot peening on the microstructure,mechanical property and reaction characteristics of Ni-Al coating.The microstructure and contact area between Ni and Al were characterized by scanning electron microscopy(SEM)and quantitative metallography analysis.The compressive mechanical properties of Ni-Al coating were measured by the universal material testing machine and split Hopkinson bar(SHPB).The reaction temperature and heat release of Ni-Al coating were tested by differential scanning calorimetry(DSC).The self-propagating reaction process and combustion speed of Ni-Al coating were analyzed by high-speed cameras.The Ni-Al energetic structural coating deposited by in-situ shot peening assisted cold spraying was dense and free from macro cracks.The shot peening effect enhanced the deformation extent of the Ni particles inside the coating and contact area between Ni and Al phases significantly while having no obvious effect on the density and composition of Ni-Al coating.The static and dynamic compression strengths of Ni-Al coating deposited by in-situ shot peening assisted cold spraying were 210~250 MPa and 310~335 MPa,separately.The reaction activity was enhanced and the reaction start temperature decreased to 422℃ with the addition of shot peening pills and the self-propagating combustion speed of Ni-Al energetic structural coating was significantly increased.As the volume of pills was 77%,the combustion speed of Ni-Al coating reached 416 mm/s,which was about five times that of Ni-Al coating without addition of cast steel pills.The in-situ shot peening assisted cold spraying can enhance the activity of cold-sprayed Ni-Al energetic structural coating without the loss of mechanical property.The combustion speed of Ni-Al coating can be enhanced significantly,while the content of shot peening pills has no obvious effect on the content of coating.