Implementation of different scanning strategy to improve the mechanical and wear properties of 15-5 PH stainless steel fabricated by laser-directed energy deposition

Abstract

In this work, the effect of three different scan patterns (island scan pattern, island alternative scan pattern and cross-hatch pattern) on mechanical and wear properties is investigated for 15–5 Precipitation-hardened (PH) stainless steel by using laser-directed energy deposition (L-DED). Six rectangular blocks are deposited with constant laser power and scanning speed. Currently, studies on the control of anisotropic behavior to improve the mechanical and wear properties by using different scan strategy, especially in the case of 15–5 PH grade stainless steel is relatively sparse. Therefore, it is necessary to learn how mechanical and wear properties are improving in these three different scan pattern samples. At first, the temperature data at a specific point is captured by using a non-contact type pyrometer during printing and the detailed microstructural characterization of that particular region is analyzed. All three different scan pattern samples mostly show δ-ferrite and lath martensite (α') structure. The X-ray diffraction shows, there is formation of secondary precipitation phases like NbCr2, NbC, and Cu rich precipitation in all three different scan pattern samples. The electron back scattered diffraction (EBSD) result exhibits the island alternative scan pattern samples have mostly mixed orientation direction, a high fraction of retained austenite (͠ 0.004) and high angle grain boundaries (HAGBs) compared to the island scan pattern and cross hatch pattern samples. The island alternative scan pattern samples show maximum improved mechanical properties i.e. average ultimate tensile strength (UTS) of 1316 MPa and up to 20% of elongation amongst all deposited samples. Similarly, the alternative island scan pattern samples exhibit a high coefficient of friction (COF) irrespective of the applied load. The SEM image of the worn surfaces clearly demonstrates abrasion and adhesion type wear in all the three different scan pattern samples.