目的 以AlSi7Mg系合金（AlSi7Mg、AlSi7MgA、AlSi7Mg1A）为代表的Al-Si系铸造铝合金广泛应用于航空器壳体零部件的制造,这类零部件在铸造成型及服役过程中容易因砂眼、磨损、腐蚀等缺陷而报废,传统热修复技术（如焊接、激光沉积等）对薄壁件的修复能力有限,探索冷喷涂修复技术的可行性。方法 采用高压冷喷涂设备,以氮气为工作气体,在AlSi7Mg1A基体上沉积AlSi7MgA涂层。通过正交试验设计,考察主要喷涂参数气体压力（3、4、5 MPa）、温度（400、500、600 ℃）对涂层显微组织、孔隙率、显微硬度,以及结合强度、抗拉强度等性能的影响规律。综合采用金相显微镜、扫描电子显微镜、显微硬度计、万能试验机系统表征涂层的显微组织、孔隙率、显微硬度、结合强度、抗拉强度。结果 气体压力5 MPa、温度600 ℃为较佳的喷涂工艺参数,在此条件下,粉末粒子变形更充分,涂层更均匀致密,孔隙率小于0.1%,平均显微硬度为(116.8±6.1)HV0.1。此外,涂层的结合强度超过(79.8±2.2) MPa（胶断）,自身抗拉强度高达321 MPa,与国标规定的T6热处理状态下AlSi7Mg1A (ZL114A)基体材料的强度相当。结论 证实仅采用较高的冷喷涂工艺参数,未使用昂贵氦气或增加其他前处理、后处理工艺,就可将普通商用粉末在AlSi7Mg1A基体上制备出兼具高致密性、高结合强度、高抗拉强度的AlSi7MgA修复涂层,这为Al-Si铸造铝合金壳体实现低成本、高性能修复提供了有效的技术方案。
Abstract
Al-Si cast aluminum alloys represented by the AlSi7Mg family (AlSi7Mg, AlSi7MgA, AlSi7Mg1A) are widely used in the manufacture of aircraft housing components. However, such components are prone to being scrapped due to defects such as porosity, wear, and corrosion during casting and service. Conventional high-energy input repair techniques, including welding and laser deposition, often induce significant thermal stress and microstructural degradation, making them unsuitable for such dimensionally sensitive components. Cold spray, as a solid-state deposition process where powder particles are accelerated to supersonic velocities and bond upon impact without melting, presents a promising low-temperature alternative. However, the application of cold spray to cast aluminum alloys faces a fundamental challenge, namely the brittle eutectic Si phases dispersed within the soft α-Al matrix tend to hinder plastic flow, contradicting the deposition mechanism that relies on severe plastic deformation. This study systematically investigates the feasibility of using this technique for the repair of AlSi7Mg alloys. The methodology involves depositing commercially available gas-atomized AlSi7MgA powder onto a grit-blasted AlSi7Mg1A substrate through a high-pressure cold spray system with industrial nitrogen as the process gas. An orthogonal experimental design is implemented to evaluate the influence of key spraying parameters-gas pressure (3, 4, and 5 MPa) and preheating temperature (400, 500, and 600 ℃) - on the coating's microstructure, porosity, microhardness, bond strength, and tensile strength. The coating is systematically characterized by optical metallography (OM), microhardness testing, tensile testing, and scanning electron microscopy (SEM). The results demonstrate that both gas pressure and temperature are crucial in determining coating quality, but temperature is found to have a more pronounced effect, with their synergistic effect leading to superior performance at higher settings. The optimal parameter combination is identified as a gas pressure of 5 MPa and a temperature of 600 ℃. Under these conditions, the powder particles undergo extensive plastic deformation, forming a highly dense and uniform coating with a porosity of less than 0.1% and an average microhardness of (116.8±6.1)HV0.1. The coating-substrate interface is clean and tightly bonded, exhibiting no discernible defects. Significantly, the adhesion strength surpasses (79.8±2.2) MPa (limited by adhesive failure in the test), and the coating's intrinsic ultimate tensile strength reaches an impressive 321 MPa. This value is not only higher than the as-cast substrate but is also comparable to the strength of AlSi7Mg1A (ZL114A) in its peak T6 heat-treated condition, as specified by national standards. This level of performance exceeds the minimum T6 strength requirements for AlSi7Mg family casting alloys in GB/T1173-2013 and reported values for nitrogen-sprayed A357/F357 coatings that rely on post-spray heat treatment. Fracture surface analysis via SEM reveals a mixed-mode failure, with both inter-particle decohesion and intra-particle ductile fracture, confirming the strong inter-particle bonding. This research conclusively proves that high-performance AlSi7MgA repair coatings, characterized by high density, exceptional bond strength, and superior tensile strength, can be fabricated using a cost-effective nitrogen-based cold spray process. This is achieved without the need for expensive helium gas or complex pre-/post-processing treatments. The findings establish a robust, economically viable, and effective technical pathway for the repair and remanufacturing of Al-Si cast aluminum alloy components, particularly within the demanding context of the aerospace industry.
关键词
AlSi7Mg /
冷喷涂 /
显微组织 /
结合强度 /
抗拉强度
Key words
AlSi7Mg /
cold-spray /
microstructure /
bonding strength /
tensile strength
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基金
中国长江电力股份有限公司资助项目（Z232402009）
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