Emre Tascioglu, Hamaid Mahmood Khan, Yusuf Kaynak, Mert Coşkun, Gurkan Tarakci and Ebubekir Koç
The present study aims to investigate the effect of finish machining and aging processes on the surface integrity of the selective laser melted (SLM) maraging steel samples and…
Abstract
Purpose
The present study aims to investigate the effect of finish machining and aging processes on the surface integrity of the selective laser melted (SLM) maraging steel samples and compared them with those obtained conventionally.
Design/methodology/approach
Finish machining and aging were applied on the SLM and wrought maraging samples to investigate and compare their microstructural and mechanical properties such as surface roughness, microhardness and wear resistance.
Findings
After applying aging and finish machining treatments, the surface roughness <1 µm, microhardness (542Hv) and wear resistance (COF 0.578) of SLM samples were similar to their wrought counterparts. Compared to finish machining, the effect of aging was more significant on the microhardness and the wear resistance, regardless of sample type.
Originality/value
The knowledge of post-processing is essential to enhance the functional performance of the SLM samples. Aging and finish machining were applied for the first time to evaluate the surface integrity of the SLM prepared maraging steel and compared it with the wrought samples.
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Onur Ertuğrul, Zafer Çağatay Öter, Mustafa Safa Yılmaz, Ezgi Şahin, Mert Coşkun, Gürkan Tarakçı and Ebubekir Koç
The purpose of this paper is to evaluate the effect of post process combinations, e.g. hot isostatic pressing (HIP) only, HIP + T6 heat treatments, and T6 only, with different…
Abstract
Purpose
The purpose of this paper is to evaluate the effect of post process combinations, e.g. hot isostatic pressing (HIP) only, HIP + T6 heat treatments, and T6 only, with different aging time, on surface properties, microstructure and mechanical properties of stress-relieved AlSi10Mg parts produced by direct laser metal sintering.
Design/methodology/approach
HIP process and HIP + T6 heat treatments were applied to as stress-relieved direct laser metal sintered (DMLS) AlSi10Mg parts. Aging times of 4 and 12 h are selected to examine the optimum duration. To analyze the advantages of HIP process, a T6 heat treatment with 4 h of aging was also applied. Densities, open porosities and roughness values of as stress-relieved, HIPed, HIP + T6, and T6-only samples were measured. The samples were characterized by OM and SEM together with EDX analysis. An image analysis study was made to evaluate the inner pore structure, thereby to understand the mechanical behavior.
Findings
HIP process does not cause a significant change in surface porosity; yet it has a positive influence on inner porosity. HIP process results in a microstructure of the aluminum matrix surrounded by a network of micron and nano size Si particles. Additional heat treatment results in larger particles and precipitation. After HIPing, ductility increases but strength decreases. Samples aged 4 h present improved yield and tensile strength but decreased elongation, yet samples aged for 12 h reach a combination of optimum strength and ductility. The lower level of tensile strength and ductility in T6-only condition indicates that HIP process plays a crucial role in elimination of the porosity thus improves the effectiveness of subsequent heat treatment.
Originality/value
The study investigates the effect of post-process conditions and optimizes the aging time of the T6 heat treatment after HIP process in order to obtain improved mechanical properties. The stress-relieved state was chosen as the reference to prevent distortion during HIPing or heat treatment.
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Hamaid Mahmood Khan, Saad Waqar and Ebubekir Koç
The current investigation aims at observing the influence of the cooling channel on the thermal and residual stress behavior of the selective laser melting (SLM)316L uni-layer…
Abstract
Purpose
The current investigation aims at observing the influence of the cooling channel on the thermal and residual stress behavior of the selective laser melting (SLM)316L uni-layer thermo-mechanical model.
Design/methodology/approach
On a thermo-mechanical model with a cooling channel, the effect of scanning direction, parallel and perpendicular and scan spacing was simulated. The effect of underlying solid and powder bases was evaluated on residual stress profile and thermal variables at various locations.
Findings
The high heat dissipation of solid base due to high cooling rates and steep thermal gradients can reciprocate with smaller melt pool temperature and melt pool size. Given the same scan spacing, residual stresses were found lower when laser scanning was perpendicular to the cooling channel. Moreover, large scan spacing was found to increase residual stresses.
Originality/value
Cooling channels are increasingly being used in additive manufacturing; however, their effect on the residual stress behavior of the SLM component is not extensively studied. This research can serve as a foundation for further inquiries into the impact of base material design such as cooling channels on manufactured components using SLM.