Effect of water atomized powder size on the flowability and sintered properties in metal binder jet 3D printing

Binder jet is one of the metal additive manufacturing methods. In this method, metal powder is used as a raw material, and a metal part is obtained by sintering a green body produced by jetting a binder on a metal powder bed leveled with a roller. Powders produced by the gas atomization method with an average particle size of around 10 mu m is mainly used in the binder jetting method for metal additive manufacturing. The water atomization method used in this study has a higher production yield, so the cost of powder is lower than that of gas atomized powder. It is also possible to produce ultra-fine powders. However, there are few studies on the use of water-atomized powder in the binder jetting method. This paper aims to evaluate the basic characterization using water atomized powder for practical use in the binder jetting method. Three different water atomized powders with average particle sizes ranging from 4 mu m to 10 mu m and the gas atomized powder with an average particle size of 10 mu m for comparison were used in the evaluation. The results confirmed that the flowability of water atomized powder decreased as the average particle size became smaller, and the flowability was lower than that of gas atomized powder due to differences in powder shape even at the same average particle size. The apparent density of the green body was found that tapped density of powder had a significant effect. The sintering process confirmed that the green body with smaller average particle size powder had higher sintering performance. This result is in line with the existing theory in the sintering technology using metal powders. It is clear that tap density and powder flowability are important for the practical use of water atomized powder in the binder jetting method.