An important development in the area of rapid tooling involves the use of massive thermal spray deposits of steel over ceramic molds to form tooling used in sheet-metal forming. Typically, the spray deposits used in this process are from twin-wire arc deposition of carbon steels. They contain a relatively high fraction of oxide, as well as carbon, rendering the material difficult to repair or modify by tungsten inert gas or metal inert gas welding, which is the usual industry practice.
Cold spraying of high-purity iron as an intermediate layer was found to permit the use of more conventional welding processes for the repair and material buildup on dies formed by the thermal spraying process. By forming a very high-purity barrier layer, the cold spray iron deposit permitted attachment of weld filler material, while isolating the difficult-to-weld underlying tool material.
Figure 13 shows an actual weld overlay on tooling material that had been previously coated with cold-sprayed iron.
This information is from ASM Handbooks Online, Vol. 5A Thermal Spray Technology, Coating Structures, Properties, and Materials. To find this information (subscription required), click on the link below and scroll down to Figure 13.
https://dl.asminternational.org/handbooks/book/12/chapter/133714/Cold-Spray-Process
