Arc spraying metal onto a master pattern is an emerging method for making molds and dies. The process, called arc spray metal tooling, involves several steps, which are shown in this paper. Three sheet metal forming dies of varying complexity were made to demonstrate and assess the process. Press tests were performed at a mold and die making facility. Arc-sprayed metal shells produced from carbon steel wire were found to have a tensile strength of approximately 23 kg/mm 2 , a Vickers hardness of 330 HV, and a dimensional accuracy of about ± 0.1 mm.

Modification of the nozzle of the arc spray equipment was attempted in order to reduce microstructural defects of the spray-formed steel shells since these defects mainly degrade the overall properties of the spray-formed tools. Based on the in-flight particle analysis, a new nozzle design of a gas shrouding concept was proposed. Effects of design factors such as nozzle dimensions and process conditions was investigated by using statistical analysis methods. The results demonstrated that the oxidation of the spray-formed steel shells can be reduced to the one-third levels of the original ones with an optimized design.

An experimental study was conducted to study the effects of properties of in-flight particles on microstructures of coating layers using a wire arc spraying system. In this study, 0.8% carbon steel wires were used for arc spraying and nitrogen gas was used as atomizing gas. Temperature, velocity and distributions of the in-flight particles were measured by DPV2000 for different working conditions. Specimens of spray-footprint were made and microstructures of them were evaluated. As a result, amount of oxide in a coating layer was proved to be related with the temperature of the in-flight particles. Because oxidation of the molten steel particles is an exothermic reaction, higher temperature of the particles during arc spraying means higher area fraction of oxide in the coating layers. For this reason, oxide level is lowest at the central area of spray footprint and it becomes higher as the distance from the center increases. Hardness, porosity and phase are changed according to the distance from the center. Abstract only; no full-text paper available.