High Cycle Fatigue Performance of LPBF 304L Stainless Steel at Nominal and Optimized Parameters.

Mohammad Masud Parvez,Yitao Chen,Sreekar Karnati,Frank Liou,Tan Pan,Joseph W Newkirk

doi:10.3390/ma13071591

Mohammad Masud Parvez, Yitao Chen + Show 4 more

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https://doi.org/10.3390/ma13071591

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Abstract

In additive manufacturing, the variation of the fabrication process parameters influences the mechanical properties of a material such as tensile strength, impact toughness, hardness, fatigue strength, and so forth, but fatigue testing of metals fabricated with all different sets of process parameters is a very expensive and time-consuming process. Therefore, the nominal process parameters by means of minimum energy input were first identified for a dense part and then the optimized process parameters were determined based on the tensile and impact toughness test results obtained for 304L stainless steel deposited in laser powder bed fusion (LPBF) process. Later, the high cycle fatigue performance was investigated for the material built with these two sets of parameters at horizontal, vertical, and inclined orientation. In this paper, displacement controlled fully reversed (R = −1) bending type fatigue tests at different levels of displacement amplitude were performed on Krouse type miniature specimens. The test results were compared and analyzed by applying the control signal monitoring (CSM) method. The analysis shows that specimen built-in horizontal direction for optimized parameters demonstrates the highest fatigue strength while the vertical specimen built with nominal parameters exhibits the lowest strength.

Highlights

Additive manufacturing (AM) has recently attained much popularity both in research and application fields such as aerospace, automobile, maritime, biomedical, and other industrial sectors [1,2,3]
Nominal and optimized process parameters were chosen to fabricate the material based on the density, tensile, and toughness test results
The fatigue test was performed for displacement control on a Krouse type miniature specimen with a dual gauge

Summary

Introduction

Additive manufacturing (AM) has recently attained much popularity both in research and application fields such as aerospace, automobile, maritime, biomedical, and other industrial sectors [1,2,3]. LPBF is capable of depositing near-net-shape internal and external complex geometries but the major drawbacks of the AM materials are the surface irregularities, residual stress, and defects such as porosity, microcracks, inclusions, dislocations, and others. They significantly influence the static and dynamic mechanical properties of a material including fatigue strength. Several studies have been carried out recently to assess the fatigue behavior of different AM materials, that is, AlSi10Mg [9,10,11,12], Ti6Al4V [13,14,15,16,17,18], Ni-based alloy [19], 15-5 PH stainless steel [20], steel [21], stainless steel [22]. Nasab et al [23] studied the effect of surface and subsurface defects on the fatigue behavior

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