Laser Deposited 18Ni300 Alloy Powder on 1045 Steel: Effect of Passes and Preheating on Microstructure

Abstract

The application of maraging steels such as 18Ni300 alloy is noteworthy for mould industries, applying repair purposes through direct energy deposition process. This objective requires microstructural characterizations and the evaluation of mechanical behaviour such as hardness. The state of substrate material, including the heat-affected zone (HAZ) and the interface between the HAZ and deposited layer, is essential, the formation of hard phases and abrupt transitions. Thus, the influence of the number of deposited layers or the pre-heating condition appears noteworthy. In the current study, microscopy observations did not reveal the presence of any crack in the cross-sections of deposited 18Ni300 alloy powder on AISI 1045 sheet steel; however, pores were observed in deposited layers. Besides, microscopic analyses revealed the achievement of a smooth HAZ in the deposited layers composed of three-layered depositions or that received preheating, confirmed by hardness measurements as well. Dilution effect ensured a metallurgical bonding between depositions and substrate, strongly affected by preheating. The HAZ microstructure, mainly martensitic transformation, distribution of chemical composition, epitaxial growth at the interface, and the size of crystals and grains were affected by preheating or the number of layers. Moreover, the heat propagation and/or dissipation across the deposited layers influenced the dendrite morphology and the texture of grains. The preheating condition provoked the formation of cellular/equiaxed dendrites that was highlighted in the three-layered deposition, increase in dendrite interspace growth.

Tensile Properties of As-Built 18Ni300 Maraging Steel Produced by DED

“…The heat released by the molten material can act as a heat source affecting the hardness of the material beneath. A similar effect was distinguished in a previous study revealing that the heat generated during consecutive layers changed the microstructure and the hardness of the heat affected zone [35]. The porosity was quantified through optical images shown in Figure 12a,b with the use of the ImageJ software, yielding results of 99.26% and 99.71% for the bottom and middle sample, respectively.…”

“…The deposition from which specimens were machined consisted on a 110 × 6 × 45 mm wall component, whose process parameters were the ones indicated in Table 2. The parameter choice was based on a previously undergone process parameter optimisation [35], as well as the existing literature on 18Ni300 DED-processing. The process parameters are shown in Table 2.…”