Cold spray technology
As an advanced solid-state coating preparation and additive manufacturing technology, cold spray technology holds a key position in the field of material surface engineering due to its unique low-temperature deposition characteristics. Unlike traditional thermal spray technology, which relies on high-temperature melting of materials, cold spray technology uses a high-speed airflow (typically 300-1200m/s) to propel metal or alloy powder particles, causing them to impact the substrate surface in a completely solid or semi-solid state. Violent plastic deformation achieves bonding between particles and between particles and the substrate. This technology fundamentally avoids the problems of oxidation, phase transformation, and grain coarsening that can occur at high temperatures, thereby maximizing the preservation of the inherent properties of the raw materials. Since its introduction by Soviet scientists in the 1980s, cold spray technology has evolved from initial laboratory exploration to industrial application after decades of development, becoming an indispensable key technology in high-end fields such as aerospace, defense, and energy and electricity.
The core advantage of cold spray technology lies in its precise preservation of material properties. For nanostructured materials, the high-temperature environment of traditional thermal spraying causes rapid nanocrystal growth, destroying their superior properties. However, the low-temperature deposition process of cold spraying perfectly maintains the stability of the nanostructure. For example, nanocrystalline aluminum coatings produced using cold spraying maintain an average grain size of 50-100 nm, achieve a hardness over 40% higher than traditional thermal sprayed aluminum coatings, and exhibit superior corrosion resistance. For heat-treated, hardened alloys such as 7075 aluminum alloy and titanium alloys, the substrate and coating temperatures during cold spraying typically do not exceed 150°C, preventing overaging or phase transformation, ensuring that the mechanical properties of the coating and substrate are perfectly matched. Experimental data from a research institute show that cold-sprayed TC4 titanium alloy coatings achieve a tensile strength exceeding 800 MPa, comparable to wrought TC4 titanium alloy. Similar coatings produced by thermal spraying exhibit a strength of only approximately 600 MPa.
Cold spray technology is applicable to a wide range of materials, from low-melting-point metals to high-melting-point alloys. For highly plastic metals such as aluminum, copper, and zinc, only relatively low gas velocities are required for effective deposition, resulting in dense coatings. For high-strength materials such as titanium alloys, nickel-based superalloys, and stainless steel, by optimizing parameters such as gas pressure, temperature, and powder particle size, coatings with high bond strength and density can be achieved. Furthermore, cold spray technology can also be used to create metal-matrix composite coatings, such as aluminum-alumina and copper-tungsten carbide. Through the synergistic effect of the different materials, the coatings possess composite properties such as wear resistance, corrosion resistance, and electrical conductivity. For example, a copper-graphene composite coating cold-sprayed on an aluminum substrate exhibits excellent electrical conductivity (reaching 90% IACS) and wear resistance 2-3 times greater than that of pure copper coatings, offering promising applications in electronic packaging.
Cold spray technology demonstrates unique advantages in coating repair and additive manufacturing. For parts repair, cold spray can precisely deposit material to restore the original dimensions and performance of components that are undersized due to wear, corrosion, or machining errors, without causing thermal damage to the substrate. An aviation maintenance company uses cold spray technology to repair engine blade tip wear. The dimensional tolerance of the repaired blades is controlled within ±0.02mm, and the fatigue life reaches over 90% of that of new parts, far exceeding the 60% achieved with traditional welding repairs. In additive manufacturing, cold spray technology can directly create complex metal components through layer-by-layer deposition, achieving a material utilization rate of over 80%, far exceeding the 10%-20% achieved with traditional forging processes. A cold spray additive manufacturing system developed by a university has successfully produced stainless steel components with complex internal cavities, achieving a density of 99.5% and mechanical properties comparable to forgings.
The development of cold spray technology is moving towards greater efficiency and intelligence. In recent years, new processes such as high-pressure cold spray and supersonic cold spray have emerged, significantly improving coating deposition efficiency and bond strength. High-pressure cold spray systems can operate at pressures of up to 3-5 MPa, accelerating powder particles to higher velocities and achieving coating bond strengths exceeding 100 MPa for high-strength materials such as titanium alloys. In terms of intelligence, by incorporating machine vision and adaptive control technologies, cold spray equipment can monitor coating thickness and uniformity in real time and automatically adjust the spray gun’s movement speed and spray distance to ensure consistent coating quality. Furthermore, the application of numerical simulation technology in the cold spray process can accurately predict particle acceleration, impact deformation behavior, and coating formation mechanisms, providing a scientific basis for optimizing process parameters. With continuous technological advancements, the cost of cold spray technology is gradually decreasing, and its application in civilian and industrial fields is expected to expand. It is expected to become a mainstream technology in future material surface engineering and additive manufacturing.
