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2475 |
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Applications of cold gas spraying compared to manual laser welding in connection with a repair contract in the aerospace field
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Peter Lutz / Bodensee Welding Consulting, BW |
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The attachment hooks of training missile wings are worn out. A technology must be found to repair the hooks. The hooks cannot be replaced. They are made of annealed steel of approx. 50 HRC hardness. A similar hardness should be achieved by the repair procedure without changing the basic material in its hardness and strength characteristics through heating. Additional annealing of the assembly is not possible due to its size. To find a solution to this problem, the cold gas spraying procedure was tested first. Cold gas spraying is a highly kinetic coating procedure in which powdery metal particles are strongly accelerated using inert gases at pressures of up to 40 bars and gas velocities far beyond 1000m/sec. When the particles hit the component surface, they form compact, strongly adherent layers of very low oxide content without preceding melting. As a second procedure, manual laser welding was tested using an Nd:YAG laser under a microscope with filling material. In this procedure, a weld pool can be generated within a few milliseconds. Due to the high velocity with which the energy is applied to the material and absorbed by it, a physical reaction is almost ruled out due to its thermal conductivity. Both procedures have the following advantages: " Function-related composition of the material applied is possible. " Due to low heating of the basic material, the characteristics of the basic material are not changed. " Repeated treatment is possible. The lecture will present the results of the procedures compared as well as limits of the respective technology in this specific application. |