Effects of build orientation and thickness of allowance on the fatigue behaviour of 15–5 PH stainless steel manufactured by DMLS

Abstract

The present study is focused on the fatigue strength of 15–5 PH stainless steel, built by Direct Metal Laser Sintering. Six‐specimen sets were manufactured, mechanically and thermally treated and tested under rotating bending fatigue. The study investigates the effects of the build orientation (parallel, perpendicular, or 45° inclined with respect to the vertical stacking direction) and of allowance for machining (1 mm or 3 mm at gage). The results, processed by an ANOVA methodology, indicate that allowance for machining has a beneficial effect on the fatigue response. Removing the surface irregularities, averagely leads to a 19% enhancement of the fatigue limit. The build orientation also becomes beneficial, when the slanted samples are included in the experiment. In this case, a fatigue strength increase up to 20% can be achieved. Further developments will include the investigation of the effects of heat and surface treatments, involving also further materials in the study.

Sensitivity of direct metal laser sintering Maraging steel fatigue strength to build orientation and allowance for machining

“…This outcome also confirms the remarks in Croccolo et al 3 The build process of a Maraging steel is performed with a doubled layer thickness (40 μm instead of 20 μm) with respect to the manufacturing of a stainless steel. In other words, this material has a particularly robust response that yields all consistent results even in different production conditions.…”

“…Five levels were considered: 0.5, 1, 2, 3, and 4 mm. For the sake of clarity, consistently with Croccolo et al, 3 a double notation has been used: The sample sets have been identified by both their sequential number and a letter (H for horizontal, V for vertical, and S for slanted), followed by a number indicating the entity of allowance. It is worth mentioning that this study must be regarded as a follow-up of the previous one included in Croccolo et al 15 : In particular, the sets with numbers 1-3 were included in that previous research.…”

“…Additive manufacturing makes it possible to achieve the production of even much complicated geometries directly from three-dimensional computer-aided design models in a short time, 1 thus remarkably reducing the time from conception to market. [3][4][5][6] Both have the capability of building metal parts layer by layer, starting from a highly controlled metal powder. These features make Nomenclature: AM, additive manufacturing; ANOVA, analysis of variance; CAD, computer-aided design; CTE, coefficient of thermal expansion; DMLS, direct metal laser sintering; FL, fatigue limit, MPa; R, stress ratio (fatigue tests); f , frequency (fatigue tests) [Hz]; R a , roughness average, μm; S i , 10-base logarithm of σ i ; S :: , overall mean (for ANOVA); SLM, selective laser melting; S-N curve, maximum bending stress vs life cycles curve in the finite life domain; SSBC, sum of squares between columns (for ANOVA); SSE, sum of squares error (for ANOVA); SSI, sum of squares interaction (for ANOVA); SSBR, sum of squares between rows (for ANOVA); UTS, ultimate tensile strength, MPa; σ i , Finite life fatigue strength for the (ith) sample set it possible to compensate the high costs for machines and for raw powder material supply.…”

Experimental Investigation on the Effect of Shot Peening and Deep Rolling on the Fatigue Response of High Strength Fasteners

“…The confidence band for a 10-90% probability of failure and a 90% confidence level was also determined and wrapped around the nominal curve for 50% failure probability. A statistical approach that was based on a generalized ANOVA for the comparison of trends, first introduced in [35] and successfully applied in [36], was also adopted to compare the fatigue strengths to the scattering of the results. As already highlighted, results were discussed within the tests that were performed in this second experimental campaign, without making comparisons with the outcomes of the previous one, due to the different material batch of the screws.…”

Fatigue Crack Growth in Maraging Steel Obtained by Selective Laser Melting

“…Studies focused on the fatigue behavior of sintered materials are relatively scarce. Most previous studies developed tested smooth specimens under stress control [1,3,4] or strain control [2]. Notched specimens have also been tested under stress control in order to obtain S-N curves [5].…”