Copper is widely used in heat exchangers, electro circuits, and mechanical parts because it has such excellent properties as high thermal conductivity and high electrical conductivity. Since copper also has excellent antibacterial and virus inactivation properties, we expect its use to increase for preventing infectious diseases on handrails, doorknobs etc., because such surfaces and items are touched by many people. Our research has focused on a laser metal deposition (LMD) method that can form a dense and highly pure layer since a laser can directly melt and solidify coating material. In this report, we review a high-speed, multi-beam laser coating method that has a low-contamination layer and demonstrate that a pure copper layer is formed on a SUS304-type stainless plate.

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We proposed a laser heating test system called the selective laser thermoregulation system to confirm the reliability of SiC/SiC ceramic matrix composites, which are expected to improve the efficiency of aircraft engines. We fabricated the proposed system and confirmed that it can heat a SiC ceramic sample to over 1400 °C and safely maintain this temperature. Furthermore, we developed AI for estimating the laser power for automatic determination of the parameters which is necessary to realize the required temperature distribution. We created datasets for machine learning by numerical simulation of laser heating and compared three types of fully connected neural networks. The AI learned the relationship between the laser power and the temperature distribution and then estimated the laser power from an untrained temperature distribution. We found that three or four layers of fully connected neural network are sufficient for realizing AI which can estimate laser power from a temperature distribution.

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Due to multi-material car body designs that have been utilized in recent years to reduce vehicle body weight, joining dissimilar materials is becoming crucial issues. We developed a new dissimilar laser lap-joining method using a cold-sprayed interlayer. In this procedure, we sprayed a steel coating onto an aluminum surface, that was laser welded to a sheet of steel. This paper reviews the recent progress of dissimilar metal joining technologies for automobiles and reports the welding phenomena in our joining method as well as its joint characteristics.

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Surface modification technology is applied in various situations, and it is a method that can be made into a multi-material by coating different materials on the material. For example, it is possible to coat a tough metal with a high-hardness material, or to combine the coating material itself to have a plurality of functions. In this report, we will explain LMD (Laser Metal Deposition), which is one of the methods, with examples for regular use.

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Laser metal deposition (LMD)，which partially forms metal layers, is a useful method for achieving multi-materialization with the correct materials in the correct places. We formed compositionally graded cemented tungsten carbides on iron-based substrates by a multi-beam type LMD piece of equipment. The multi-beam type LMD can change the amount of energy applied by laser irradiation into the powder by changing the intersecting position of the beams. We clarified that the dispersity of the tungsten carbide (WC) particles was improved by moving the laser-focusing position from the substrate’s surface to 0.5-mm of overfocus position. We found that the average WC particle size increased by setting the overfocus position and could be controlled by the laser-focusing position of the multi-beam lasers.

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Joining technology for metals and dissimilar materials is attracting attention in various industrial fields. In the automotive industry, the joining metals and plastics is especially expected to be a key technology for weight reduction. A new joining technology of metal to plastics has been developed by laser surface processing to metal. Such processing is done by a continuous-wave (CW) single-mode fiber laser. In this paper, we introduced the results of studies aimed at the mechanism’s solution of unevenness formation in metal surface processing technology (DLAMP®) with a CW single-mode fiber laser and an airtight mechanism’s solution for joining metal and resin.

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The spectral bandwidth was suppressed effectively and the wavelength was stabilized in a high-brightness fiber-coupled laser diode (LD) with an external cavity configuration consisting of an aspheric lens and a volume Bragg grating. The wavelength shift in the external-cavity fiber-coupled LD with variation in current was reduced from 0.98 to 0.018 nm/A. During operation at a drive current of 5.5 A, the external- cavity fiber-coupled LD’s bandwidth was reduced from 1.87 to 0.16 nm and output power of 4.19 W was obtained. The locked power spectral density of the external-cavity fiber-coupled LD increased from 2.4 W/nm to 2619 W/nm.

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