1. Field of the Invention
One aspect of the present invention relates to a method of producing deposits on a surface.
2. Background Art
Spray-forming is one technique for producing prototype tooling, for example dies and molds. Other uses include application of protective coatings and repair of articles. A typical spray-forming technique includes the steps of (1) providing a substrate in the pattern to be produced, (2) spraying a melted material on to the substrate, (3) allowing the melted material to solidify into a deposit having the shape of the pattern, and (4) repeating steps (2) and (3) until sufficient solidified material has accumulated for the intended application.
These processes expose a substrate to significant inputs of heat that may damage substrates and surfaces susceptible to heat.
As a consequence, a conventional flame spray gun is typically held at least 150-mm to 200-mm from the substrate. Therefore, there is less control spatially of the spray, especially in tight corners, as well as less control of the side reactions and cooling in flight. The result of the variation of cooling in flight is a less homogeneous coating on the surface, and reduced efficiency of use of materials in the deposit.
A further consequence of the longer flight can be a greater propensity to generate oxides in the melted material through reaction with ambient air. When oxides are formed, the hardness of the surface increases because of the increased hardness of the oxide. However, the tensile strength of the resulting surface will typically be lower.
In light of the foregoing, what is needed is a method for generating fine particles of melted materials and applying them to a candidate substrate for heat damage without significantly degrading the applied material or the substrate.
What also is needed is a method that reduces the compromise between hardness of the surface due to particulate adjuvants, and the lower tensile strength of the coating due to the presence of oxides.
What is further needed is a method that provides improved spatial control, deposit efficiency, and materials property control of materials deposited on a surface of a substrate as well as reduced residual stress and relief of existing stress in substrates and material deposits.