Mustafa Safa Yılmaz, Gökhan Özer, Zafer Çağatay Öter and Onur Ertuğrul
This paper aims to investigate the effects of various heat treatments on microstructure, hardness, porosity and corrosion properties of the parts.
Abstract
Purpose
This paper aims to investigate the effects of various heat treatments on microstructure, hardness, porosity and corrosion properties of the parts.
Design/methodology/approach
Hot isostatic pressing (HIP) process, various heat treatments and their combinations were applied to the AlSi10Mg parts produced by direct laser metal sintering (DMLS).
Findings
It has been found that the HIP process, which is a post-processing process, reduces the amount of porosity in DMLS-AlSi10Mg material, thus improves corrosion resistance significantly.
Originality/value
In this study, the HIP process and subsequent T6 heat treatments were applied to AlSi10Mg parts produced by the DMLS technique. The study aims to increase the corrosion resistance of AlSi10Mg parts by reducing porosity with the HIP process and by altering the microstructure with the T6 process.
Details
Keywords
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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Ertugrul Durak and Hakan Ali Yurtseven
This paper aims to design and manufacture a wear-test rig performing reciprocating movement that is more relevant to the elevator brake system. Also, a sample test result that was…
Abstract
Purpose
This paper aims to design and manufacture a wear-test rig performing reciprocating movement that is more relevant to the elevator brake system. Also, a sample test result that was conducted in this experimental set-up is presented to evaluate the tribological properties of the brake linings of the elevator system that are activated in emergencies.
Design/methodology/approach
The brake linings are some of the most important security elements in elevators. The friction and wear properties of these brake linings have great importance for both safety and comfort. Elevator brake linings are often used in conjunction with guided rails under dry and boundary lubrication conditions. Therefore, friction coefficient and wear types occurring in the brake linings may be different. The tribological properties of the brake lining material in the literature are generally identified using a pin-on-disc wear-tester. The pin is contacted by rotating a disc in this wear-test rig. However, as the brake linings and guide rails do not have a reciprocating movement (linear translational motion) on each other, this wear-test rig is not suitable for brake linings and guide rails in the elevator system.
Findings
A sample test result that was conducted in this experimental set-up is presented to evaluate the tribological properties of the brake linings of the elevator system that are activated in emergencies. In these experiments, three different brake lining materials that are widely used in the elevator car guide rails in Turkey were tested under different speeds and loads.
Originality/value
The paper provides information about how to evaluate the tribological properties of the brake linings of the elevator system that are activated in emergencies. Also, it offers practical help for the manufacturer and researcher in the elevator sector.