The manufacturing of hard tools from metallic powders by selective laser melting

To make strong metallic parts directly from metallic powders, the selective laser melting method, in which metallic powders are successively melted and solidified in a microscopic zone, is proposed. From a series of tests on some metal powders, two types of solidified shapes are observed: successive balling and linear solidification. The second is suitable for the process. A nickel alloy powder used for cladding steel surfaces is found to be a good candidate for making dies. In making 3D shapes, deflection and cracking ale caused in the product by rapid heating and quenching. To solve the problems, a dual laser scanning system in which YAG and CO2 laser beams are offset a small amount from each other and scanned is proposed. From the results of three-point bending tests and Vickers hardness measurements on formed linear specimens, reheating by CO after heating by YAG improves the material's propel ties. It is considered that slow cooling or reheating after melting can eliminate residual stress and improve ductility. (C) 2001 Elsevier Science B.V. All rights reserved.