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This paper describes the establishment of an evaluation method for metal surface texture. The evaluation parameters used for surface texture were roughness, glossiness and color. Seven sample materials were studied: aluminum alloys (A2017, A5052), stainless steel (SUS304) and copper alloys (tough pitch copper C1100, brass C2801, phosphor bronze C5191 and nickel silver C7541). The surfaces of all specimens were polished using waterproof abrasive papers. The correlation of the surface texture parameters for all specimens was investigated experimentally. The surface roughness of specimens was evaluated using the arithmetical mean roughness ''Ra''. The method for evaluating surface color was assessed by using CIELAB color space. The CIELAB color space is one of a uniform color space defined by CIE (Commission Internationale de l'Eclairage) in 1976. The results indicated that as surface roughness value ''Ra'' decreased, as the glossiness value ''Gs(60)'' increased exponentially. The lightness value ''L Ã '' of the CIELAB color space decreased, as surface roughness value ''Ra'' decreased. Thus, the relationship between the lightness value ''L Ã '' and surface roughness value ''Ra'' showed an inverse correlation with the glossiness value ''Gs(60)'' and surface roughness value ''Ra''. Moreover, the surface color showed that the blue hue increased, as the surface roughness value ''Ra'' decreased for all seven types of materials.

Selective laser melting (SLM) process has advantages in building free shape and simplification of manufacturing process. Since Ni-base superalloys have lower ductility at lower temperature, it is difficult to produce the parts by means of other process like forging. Therefore, SLM process has already applied to produce Ni-base superalloy parts. However, SLM process needs a long process time comparing to casting and machining. One of the means to solve this problem is an application of the high scanning speed condition under high power laser output. In this research, the optimum fabrication condition of Inconel 718 superalloy by SLM process under high power and high scanning speed condition was investigated. As a result, the optimum fabrication condition was obtained using the process map. However, the relative density of the as-built specimen fabricated under high power and high scanning speed condition is lower than that of the as-built specimen fabricated under the condition of 300 W and 600 mm/s. This may be mainly due to the occurrence of gas-pores by key-hole like phenomenon in melt pool and the increase of spattering at high power and high scanning speed condition.

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Recently, high-entropy alloys (HEAs) have attracted much attention because of their superior properties, such as high strength and corrosion resistance. This study aimed to investigate the influences of process parameters on the microstructure and mechanical properties of CoCrFe NiTiMo HEAs using a laser-based powder bed fusion (LPBF) process. In terms of laser power and scan speed, a process map was constructed by evaluating the density and surface roughness of the as-built specimen to optimize the process parameters of the products. The mechanical properties of the as-built specimens fabricated at the optimum fabrication condition derived from the process map were evaluated. Consequently, the optimum laser power and scan speed could be obtained using the process map evaluated by density and surface roughness. The as-built specimen fabricated at the optimum fabrication condition presented a relative density of more than 99.8%. The microstructure of the as-built specimen exhibited anisotropy along the build direction. The tensile strength and elongation of the as-built specimen were around 1150 MPa and more than 20%, respectively.

Metal additive manufacturing technology requires a real-time monitoring and feedback control system to assure the quality of the final products. In particular, it is essential to reveal the phenomena of recoating and melting-solidification processes in laser powder bed fusion using a real-time monitoring system because they influence strongly the occurrence of defects. This study was conducted to elucidate the correlation among the powder characteristics, recoating conditions, and surface morphology of a powder bed in the recoating process to determine the relationship between the surface morphology of the powder bed and the final product quality. To this end, a surface morphology measurement system composed of a powder recoating test bench and a layer surface morphology measurement apparatus was first designed and fabricated. Then, it was used to quantify the surface morphology of the powder bed. Specifically, the influences of the different powder characteristics and the recoating parameters of the powder supply ratio and recoating speed on the surface morphology of the powder bed were investigated using various powders of Al-10Si-0.4Mg (AlSi10Mg) alloy and Inconel 718 (IN718) alloy. The surface morphology of the powder bed was measured as the value of 2σ at a resolution of 30 μm in height. It was found that the angle of repose and the basic flow energy of the bulk powder are promising parameters for evaluating the surface morphology. The surface morphology was significantly affected by the powder characteristics and recoating speed. The value of 2σ for the AlSi10Mg powder increased rapidly over a recoating speed of 50 mm/s for all powders. The value of 2σ for the irregularly shaped AlSi10Mg powder was approximately 19 μm, and the 2σ values for the other powders were approximately 17 μm at a recoating speed of 15 mm/s. However, at a recoating speed greater than 300 mm/s, the irregularly shaped powder exhibited better surface morphology than did the spherical powder. The recycling process deteriorated the flowability of the new powder. However, the surface morphology of the spherical recycled powder was similar to that of the spherical powder. Consequently, the correlation among the powder characteristics, recoating conditions, and surface morphology of the powder bed was revealed by employing the surface morphology measurement system. Quantification of the surface morphology of the powder bed using the monitoring system facilitates control of the recoating process to prevent the occurrence of defects.

This paper describes a quantitative evaluation method for metal surface texture. We used surface roughness and glossiness as parameters to describe surface texture. Specimen surface roughness was evaluated based on geometrical product specification data taken from japanese industrial standards. The effects of surface roughness on glossiness were investigated by aluminum alloys. The relationship between the glossiness and the roughness height, the period of the roughness profile and the slope for the surface roughness processed by a vertical milling machine were studied for determining if the topography of the surface roughness affects the glossiness. The surface of the specimens were polished using abrasive paper and blasted, so that the arithmetical mean deviation, Ra, was less than 1.00 mm. The effects of roughness on glossiness were investigated on polished surfaces and blasted surfaces. The results show that the surface roughness shape and the glossiness prove to be effective indices for evaluating the surface textures of aluminum alloys.

Laser powder additive manufacturing (PBF-LB) is an additive manufacturing method capable of producing high-precision and fully dense parts. However, nondestructively quality assurance of no internal defects remains challenging. Mitigating internal defects requires elucidating their formation mechanism and improving the PBF-LB process conditions. Therefore, we developed an in-situ monitoring system that combines surface morphology measurement by fringe projection and thermal field measurement with a high-speed camera. On heterogeneous surfaces in a practical multi-track PBF-LB process, a roughness index of the built part surface altered cyclically, consistent with the change in the angle between laser scanning and atmospheric gas flow. The high-speed camera monitoring showed that the melt pool was asymmetrical and spindle-shaped and that spatter was emitted mainly from the built part side of the melt pool. Furthermore, it was found that the built-part surface morphology under the powder layer affected the stability of the melt pool. As a result, a graphical representation of the melt pool and spattering for heterogeneous surfaces was proposed. Although it is still difficult to theoretically estimate the process window in which no spattering and no internal defects, in-situ monitoring equipment will provide knowledge to elucidate spattering and internal defects formation.