Laser-assisted machining of Inconel 718 with an economic analysis

Superalloys have high strengths at elevated temperatures, which make them attractive toward various applications and also make these materials difficult to machine at room temperature due to excessive tool wear and poor surface finish. Laser-assisted machining (LAM) offers the ability to machine superalloys more efficiently and economically by providing the local heating of the workpiece prior to material removal by a single point cutting tool. An existing transient, three-dimensional heat transfer model is modified for modeling LAM of Inconel 718. Suitable coating conditions are determined for increasing the laser absorptivity in metals and an approximate absorptivity value is determined. The thermal model is validated in axial and circumferential directions by temperature measurement using an infrared camera. The machinability of Inconel 718 under varying conditions is evaluated by examining tool wear, forces, surface roughness, and specific cutting energy. With increasing material removal temperature from room temperature to 620 degrees C, the benefit of LAM is demonstrated by a 25% decrease in specific cutting energy, a 2-3-fold improvement in surface roughness and a 200-300% increase in ceramic tool life over conventional machining. Moreover, an economic analysis shows significant benefits of LAM of Inconel 718 over conventional machining with carbide and ceramic inserts. (c) 2005 Elsevier Ltd. All rights reserved.