Review of Laser Deposited Superalloys Using Powder as an Additive

Abstract

In this paper laser metal deposition (LMD) with blown powder was reviewed with respect to the material behavior of nickel and nickel-iron based superalloys. The key benefits of LMD are claimed to be increased design freedom of components as well as reduced environmental impact since it enables near net shape manufacturing. This review considers the LMD processing parameters such as laser power, powder feed rate, spot size, standoff distance, and traverse speed, together with aspects related to the powder e.g. morphology, porosity, inclusion and satellite content. Special emphasis was put on how these parameters affect the deposit and substrate in terms of cracking, porosity, inclusions, phase transformations, and other material related phenomena. A characteristic microstructure of LMD deposited superalloys has a columnar dendrite growth in the vertical build up direction. The grain growth can however be manipulated, making it more equiaxed by, for instance, altering process parameters and/or scanning path. Residual stresses in LMD samples are unevenly distributed and large residual tensile stresses can be found at the surface of the deposit while large compressive stresses are located close to the substrate in the core of the deposit. One of the most important parameter is considered to be the specific energy input which largely influences the m elt pool during deposition which in turn can be related to the microstructure, residual stress and, process related defects such as porosity, cracking, lack of fusion and, dilution.

Effects of preheating and cooling on the crack defects of laser solid formed Rene 104 superalloy parts

“…Moreover, the production cost and fabrication time are significantly reduced because of the simplified forming and machining processes. 5–10 Given the notable improvement in production flexibility, LSF is a promising method for manufacturing Rene 104 superalloy components.…”

Laser direct energy deposition – the effect of process parameters on inconel 718

“…An overview of DED-L parameters is presented in Figure 2. Complex relationships exist between DED-L process parameters and the deposited materials properties (Segerstark, Andersson, & Svensson, 2014;Zhang & Jung, 2018). Process parameters affect the melt-pool characteristics, which regulates material fusion and the microstructure (Segerstark, Andersson, & Svensson, 2014).…”

“…Complex relationships exist between DED-L process parameters and the deposited materials properties (Segerstark, Andersson, & Svensson, 2014;Zhang & Jung, 2018). Process parameters affect the melt-pool characteristics, which regulates material fusion and the microstructure (Segerstark, Andersson, & Svensson, 2014). DED-L process parameters are typically determined by depositing numerous individual tracks using different process parameters combinationsthis is a lengthy process, and what may produce a good quality track deposit does not guarantee the same quality in a larger build.…”

“…Processing defects include porosity, cracks, residual stress, distortion, and anistropy. These are influenced by the thermal cycling and heat build-up within the deposit (Segerstark, Andersson, & Svensson, 2014).…”

“…Smaller particles heat up faster than larger particles, increasing the probability that they are completely molten when entering the melt-pool. Larger particles which are not fully molten are more likely to contain gas inclusions which cannot escape (Segerstark, Andersson, & Svensson, 2014).…”