The contact surface of thermal spray significantly affected bonding strength and coating elasticity. This work aimed to evaluate the effects of contact surface conditions characterised by substrate surface profile and spray pressure on the bonding and buckling strength of aluminium thermal sprayed on the low-carbon steel substrate. The SS400 low-carbon steel substrate was profiled using the milling process to form the V, small V, U, and flat profiles that were subsequently roughed by employing the sandblasting process. A coating comprising 99% aluminium was sprayed onto the substrate surface with different spraying pressures of 3.5, 4.5, and 5.5 bar. Pull-off and buckling tests were performed for determining thermal spray characteristics. The results of this work showed that the optimal bonding strength of the coating was obtained for the thermal spray specimen that had a flat substrate surface, and the spraying pressure was set to 5.5 bar. Generally, low spraying pressure lead to be low bonding strength and vice versa. Profiled surface was not profitable on the mechanic properties of thermal spray bonding.

The effect of shielding gas composition and welding current on the mechanical-physical properties of plug welding joint stainless steel SUS 304L has been investigated. Metal Inert Gas (MIG) welding was used to join SUS304L with a thickness of 3 mm. The variations of welding current were 80 A, 100 A, and 120 A, while variations of shielding gas composition were 100% Ar; 92,5% Ar-7,5% CO2; 85% Ar-15% CO2; 77,5% Ar-22,5% CO2; 100% CO2. Macro and microstructural tests were conducted to determine welded joints physical properties. Tensile-shear testing and micro hardness Vickers were done to determine welded joints physical properties. The results show that the higher level of welding current and CO2 content in the shielding gas, the more tensile-shear load bearing capacity and decreased hardness. The welding current of 120 A and shielding gas 77,5% Ar-22,5% CO2 produced welded joints with the highest tensile-shear load bearing capacity. The nugget size increased as the higher level of welding current and the CO2 content in the shielding gas due to the increase of heat input.

ABSTRAK Revolusi Industri 4.0 tidak hanya menitik beratkan kepada penguasaan teknologi, namun juga mendorong untuk terbentuknya kepribadian yang siap bekerja sama, disiplin, berpikiran luas dan kritis. Selain tempat untuk menimba ilmu pengetahuan, sekolah juga merupakan tempat siswa membentuk kepribadian yang siap menghadapi revolusi industri. Dari hasil observasi telah didapatkan permasalahan utama yaitu siswa terlambat masuk ke ruangan kelas dan waktu yang diperlukan untuk mengerjakan absensi oleh tenaga pengajar secara manual. Untuk mengatasi ini diusulkan sebuah solusi berupa absensi mempergunakan RFID yang akan di integrasikan dengan Microsoft Exel. Sistem bekerja pada kartu yang sudah diprogram pada Arduino Uno. Masing-masing siswa mendapatkan kartu yang dapat di pergunakan ketika masuk dan keluar ruangan kelas. Dari hasil pengujian kegunaan, didapatkan hasil yang positif dari siswa dan guru, dimana kedepannya guru dapat lebih efektif dalam memanfaatkan waktu untuk mengajar dan merekap absensi siswa nantinya.

Due to lightweight and strong, aluminum is often applied to the car bodies of an automotive and high-speed train. Welding is the main manufacturing process for these structures. Environmental conditions in welding, especially airflow velocity, humidity, and temperature, significantly affect the impact property of aluminum alloy weld joints. In this work, the welding environment is controlled by creating an insulating welding room where the airflow velocity, humidity, and temperature of the welding environment can be adjusted to obtain an ideal welding environment. The variation of welding environment conditions used was the temperature of 17°C, 22°C, and 27°C; relative humidity of 64%, 68%, and 72% and airflow velocity of 1.1m/s, 1.6m/s, and 2.1m/s. The results showed that the lower the welding environment temperature, the more toughness decreased. The lower the flow rate and the relative humidity of the surrounding air, the tougher it is. Air humidity contains a lot of water vapor (hydrogen) which can cause porosity. The low temperature of the welding chamber results in a shorter freezing time of the weld metal, resulting in cracking and porosity in the weld metal. The ambient airflow velocity interferes with the shielding gas function so that the outside air can be contaminated in the weld metal. The best welding environmental conditions will be achieved if the airflow velocity is below 1.1 m / s, the relative humidity is below 64% and the ambient temperature is 27°C.

Quenching is a swift way of returning metal back to ambient temperature in order to acquire a certain property. Although it is often used to enhance the hardness of metals and their micro-structure, it equally causes a serious variation in the mechanical and physical properties of the metals. This research focuses on quenching media's effect on the microstructure and mechanical properties of a 150mm x 80mm x 8mm welded mild steel plate through microscopic examination, metallography mounting, surface grinding, and surface polishing. Microstructural analysis with hardness and impact test was carried out on the steel plate using water, air, and oil as the quenching media. The results of the test show the Vickers Pyramid Number (HV) for water, oil, and air to be 284.2, 270.9, and 262.2 HV for the base metal, heat affected zone (HAZ), and weld metal (WM), respectively. The amount of energy absorbed by the three specimens during fracture is 23.12, 25.27, and 26.83 J, respectively. The test further indicates that the water-quenched media exhibited mostly martensitic structures and held back austenite with many structures of cementite while the oil and air media exhibited martensite phase and refined grains structures individually. It is therefore concluded that air is more suitable to cool the weld metal for damping applications in engineering.