Metallic Powder Manufacture for Conditioning Cast Iron as an Additive Manufacturing Substrate

The main purpose of this work is to design and develop a metallic powder to use it as a paint for cast iron moulds allowing subsequent L-DED deposition on the parts to increase corrosion resistance and/or wear resistance. Cast iron is widely used in the manufacturing of several components with complex geometry and cavities due to its good castability, low cost and excellent machinability. Currently, different technologies of surface modification are used to increase the wear and/or corrosion resistance, but there are still many problems such as limitation on coating thickness, high cost and complex equipment [1]. L-DED (Laser Direct Energy Deposition) has been proposed as a potential solution without substantially increasing the price. However, L-DED on cast iron components is a difficult and a complex process due to the risk of heterogeneous thermal and stress fields formation as result of the graphite and matrix properties, formation of pores for carbon dioxide produced during the laser beam radiation and the formation of hard and brittle phases due to the high cooling rate that may lead to crack formation [2].

An intermediate coating with Ni-rich powder is proposed. For that, a Ni-3Ti wire of Ø 1 mm has been atomized in the ATO Lab+ metal powder atomizer in Azterlan using the 35 kHz ultrasonic module and the following process parameters: argon flow 20 l/min, 70 % power pump, 100 A arc intensity and 80 % ultrasonic amplitude. Table 1 compares the chemical composition of both Ni-3Ti wire and powder. Apart from minor variations, the most important change was the fading of Mn (~38 %).