Powder Technology, Vol.340, 449-458, 2018
Development of powder distribution model of discontinuous coaxial powder stream in laser direct metal deposition
For laser direct metal deposition (LDMD) process, a general powder distribution model of discontinuous coaxial powder stream (DCPS) was developed based on homogeneous transformation. An image-based powder measurement (IBPM) technique, whose illumination light is a cylindrical light, was used to acquire powder distribution characteristics. A set of data preprocessing methods were proposed to validate the developed model. Correlation analysis indicated that the matching coefficients between the measured and simulated data are above 0.99 on the axial plane of the coaxial powder stream, whereas above 0.95 on the cross-sections near the focal spot. The error of the predicted focal spot position was less than 1%. Mean sensitivity indexes inferred that both the injection radius and the injection angle of the powder-fed head have significant influence on the focal spot characteristics of the DCPS compared to the nozzle exit diameter. Reducing the focal spot diameter can improve the powder utilization efficiency. For achieving safe deposition process and stable powder delivery, the standoff distance at the focal spot should be greater than 6 mm. (C) 2018 Elsevier B.V. All rights reserved.