Selective Laser Melting and Mechanical Properties of Stainless Steels

Abstract

Metal additive manufacturing (AM) has been evolving in response to industrial and social challenges. However, new materials are hindered in these technologies due to the complexity of direct additive manufacturing technologies, particularly selective laser melting (SLM). Stainless steel (SS) 316L, due to its very low carbon content, has been used as a standard powder in SLM, highlighting the role of alloying elements present in steels. However, reliable research on the chemical impact of carbon content in steel alloys has been rarely conducted, despite being the most prevalent element in steel. Considering the temperatures involved in the SLM process, the laser–powder interaction can lead to a significant carbon decrease, whatever the processing atmosphere. In the present study, four stainless steels with increasing carbon content—AISI 316L, 630 (17-4PH), 420 and 440C—were processed under the same SLM parameters. In addition to roughness and surface topography, the relationship with the microstructure (including grain size and orientation), defects and mechanical properties (hardness and tensile strength) were established, highlighting the role of carbon. It was shown that the production by SLM of stainless steels with similar packing densities and different carbon contents does not oblige the changing of processing parameters. Moreover, alterations in material response in stainless steels produced under the same volumetric energy density mainly result from microstructural evolution during the process.

Characterization of Microstructural and Mechanical Properties of 17-4 PH Stainless Steel by Cold Rolled and Machining vs. DMLS Additive Manufacturing

“…These methodologies have undergone extensive investigation to elucidate their impact on material performance, considering factors such as porosity [26], process parameters, building atmosphere, post-heat treatments, and initial powder characteristics. These investigations have focused on phase transformation, microcrack formation, microstructure evolution, and mechanical properties, particularly in stainless steel materials [27][28][29]. Additionally, comparative studies have been undertaken regarding similar AM technologies.…”

“…The hardness value obtained was 298 ± 3.8 HV for rolled and 312 ± 8.76 HV for AM, similar to those obtained by other authors. For example, Gatoes mentions a range of 250-460 HV for rolled and 306 ± 11 HV for AM [28], while Akessa reports a hardness of 331 ± 28 HV for AM material [31].…”

“…According to the experimental and simulated and experimental tests, the DMLS 17-4 PH compared with the rolled 17-4 PH stainless steel samples decreased the yield strength by ~8% and ultimate strength by ~11%. This mechanical behavior could be attributed to defects in the DMLS process, such as defects due to unfused voids and porosity [28,29]. The results provided by simulation fit with those from experimental analysis; this is due to the integration of the experimental values (elastic modulus, tensile strength, yield strength of material, and the average experimental stress-strain curves) into the numerical model to predict the mechanical properties of the material and generating information about the mechanical properties of the materials.…”

Emerging Materials for Additive Manufacturing

“…In their review article, Minasyan and Hussainova discussed the recent developments of ceramic particulate-reinforced aluminium alloys produced by laser powder bed fusion [14], while Hou et al elaborated the use of monitoring systems for powder bed fusion processes with a focus on metals in their comprehensive review [15]. For original research, Gatões et al studied the fabrication of different stainless steels using selective laser melting, a type of laser powder bed fusion technique [16]. In their study, Mally et al benchmarked the mechanical properties of ferritic steels produced by selective laser melting with relevant forged parts [17].…”