Abstract
In the thermal spraying process, the process for the molten metal particles to hit against matrix to form coating experiences great change temperature. Since the coating materials has different thermal physical properties with the matrix materials, the residual stress is surely left in the coating. Much bigger residual stress not only restricts coating thickness but also primarily affects coating binding strength. Having analyzed reason for residual stress in the thermal spraying coating and matrix, the theoretical model of arc spraying 3Cr13 molten drop impact stress is built and numerical simulation is done for this theoretical model. The result indicates that: the faster the molten drop speed is, the greater the pressure that matrix produces. When the molten drop's collision speed is 100m/s, it is not obvious for the matrix's pressure stress and when the collision speed is increased to 200m/s, the pressure stress produced in the matrix can maximize 5500Mpa; the faster the molten drop's collision speed is, the higher extent the molten drop's flattening is, which is more beneficial to increase coating’s bonding strength. The radius for the molten drop in the radius of 35μm becomes 80~110μm after collision and the flat ratio of the molten drop particle is about 3. The theoretical analysis is consistent with the experiment result.
Highlights
Stress is generated for deforming of the molten drop particle colliding against the matrix in a high speed or the coating for bearing particle’s impact [1-7]
While the residual stress produced by collision is in linear relation with the impact strength [8]:
The faster the spraying speed is, the bigger the pressure stress produced in the matrix. It can be seen from the result that when the molten drop’s collision speed is 100m/s, the matrix’s pressure stress is not obvious; when the collision speed is increased to 200m/s, the pressure stress produced in the matrix can maximize 5500MPa at its maximum
Summary
Stress is generated for deforming of the molten drop particle colliding against the matrix in a high speed or the coating for bearing particle’s impact [1-7]. While the residual stress produced by collision is in linear relation with the impact strength [8]: peening = KEk [2]. In the formula, K is live load coefficient in collision It can be seen from Formulas [1] and [2] that, the faster the particle’s speed is, the greater its kinetic energy is, to produce greater residual stress in the collision. Since the molten particle collides the deposit in a high speed, stress is generated by the matrix or the formed coat deforming for bearing the impact pressure. Due to the restriction for the current equipment to test single molten drop’s stress and deformation, the numerical simulation method is adopted in the paper to simulate single molten drop’s deformation process and
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