An investigation on porosity in laser metal deposition

Abstract

Laser metal deposition is a process that involves laser processing of fine metal powders into forming three-dimensional structures. Its versatility offers immense opportunities in numerous applications. However, the deposited material using the blown powder process is often plagued by inherent defects such as porosity, which cannot be tolerated in certain applications. The origin of the gas porosity observed in laser deposited material is not entirely certain, and hence it presents difficulties in tackling this problem. In this work, a comprehensive investigation of porosity is carried out using gas atomised Inconel 718 powder. A series of experiments using the central composite design is used to examine the complex relationships between the processing factors that affect porosity in laser metal deposition. In the analysis, a clear distinction is made between the two types of porosity; namely lack of fusion and gas porosity. The results show that the two types of porosity are attributed by different factors. The gas porosity, which is more difficult to eliminate than the lack of fusion, can be as high as 0.7%. Through optimisation, the gas porosity can be reduced to 0.037%, and the lack of fusion can be completely avoided.Laser metal deposition is a process that involves laser processing of fine metal powders into forming three-dimensional structures. Its versatility offers immense opportunities in numerous applications. However, the deposited material using the blown powder process is often plagued by inherent defects such as porosity, which cannot be tolerated in certain applications. The origin of the gas porosity observed in laser deposited material is not entirely certain, and hence it presents difficulties in tackling this problem. In this work, a comprehensive investigation of porosity is carried out using gas atomised Inconel 718 powder. A series of experiments using the central composite design is used to examine the complex relationships between the processing factors that affect porosity in laser metal deposition. In the analysis, a clear distinction is made between the two types of porosity; namely lack of fusion and gas porosity. The results show that the two types of porosity are attributed by different facto...