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Titanium tends to form nitrides and carbides. The plasma nitrocarburizing technique can generate these nitride and carbide compounds on the material's surface. The objective of this research is to use a plasma nitrocarburizing process to increase the hardness and corrosion resistance of commercially pure titanium. The generation of a thin layer with an average thickness of 1.88 μm was discovered using a Scanning Electron Microscope. The X-Ray Diffraction technique identifies this thin layer made of TiN and TiC compounds. The untreated commercially pure titanium hardness was 105.75 VHN, and the plasma nitrocarburized commercially pure titanium hardness was 312.68 VHN, according to the Vickers micro tester. After plasma nitrocarburizing, the corrosion rate of untreated commercially pure titanium decreased from 0.0061 mmpy to 0.00077 mmpy. The plasma nitrocarburizing process resulted in a 196 percent increase in hardness and an 87 percent reduction in corrosion rate.

Pada penelitian ini menggunakan material aluminium dengan ketebalan 4 mm dan diameter 16 mm. Pada proses elektroplating ini menggunakan variasi waktu dan voltase. Variasi waktu pada lapisan Cu (tembaga) adalah 30, 45, 60, 75, dan 90 menit dan pada lapisan Ni (nikel) 30 menit. Untuk variasi voltase Cu dan Ni sama-sama menggunakan 3V. Pengujian kekerasan dilakukan menggunakan mikro-vickers hardness tester, pengujian keausan dilakukan menggunakan oghosi universal wear testing mechine (type oat-U). Hasil dari pengujian ini membuktikan bahwa proses elektroplating dapat menaikan nilai kekerasan dari bahan sebelum dilapisi 76,82 VHN, setelah dilapisi mendapatkan nilai optimum menjadi 224,32 VHN dari variasi Cu= 90 menit, Ni= 30 menit, dan v= 3V. Begitu pula pada uji keausan mengalami peningkatan di mana sebelum dilakukan proses elektroplating 1,749 x 10-4 mm2/kg. Setelah dilakukan proses elektroplating meningkat menjadi 3,126 x 10-5 mm2/kg.

Pengerasan logam dengan treatment Quenching merupakan proses pendinginan secara cepat, dari temperatur austenisasi (umumnya berkisar antara temperatur 815 o C – 870 o C). Tujuan dari proses ini adalah untuk meningkatkan nilai kekerasan pada suatu logam. Proses quenching yang dilakukan dengan cairan garam. Garam dipakai sebagai bahan pendinginan dikarenakan memiliki sifat mendinginkan yang teratur dan cepat, cairan garam merupakan larutan garam dan air. Hasil pengujian komposisi kimia bahwa, logam S09CK dikategorikan dalam baja karbon rendah. Hasil pengujian tarik menunjukkan material yang di quenching memiliki sifat yang lebih getas dibandingkan dengan raw material. Dari hasil pengujian kekerasan nilai rata-rata dari material yang di quenching sebesar 207.6 VHN pada bagian permukaan 186.6 VHN pada bagian sisi dan raw material 199 VHN dan 113.3 VHN. Hasil foto mikro fasa yang terbentuk adalah ferit dan perlit.

Garbage is a serious problem if it is not managed properly, both organic and non-organic. Inorganic waste, for example, plastic, metal, glass, and charcoal from coal combustion are difficult to decompose in the soil. HDPE (high-density polyethylene) plastic is one type of inorganic waste that is difficult to decompose, but this plastic can be recycled. The objective of the study is to develop light cement blocks by using the waste of HDPE, coal bottom ash and cement. The research guide was referred to SNI (Indonesian National Standard). The SNI-03-6825-2002 is for testing of the compressive strength and SNI 03-0349-1989 for the testing of the water absorption. The size of the specimen was 5 x 5 x 5 cm. In this study, the compositions of HDPE: coal bottom ash were varied by 70%: 0%, 60%: 10%, 50%: 20%, and 40%: 30%. The Holcim cement was 30% of the volume fraction. Testing was conducted after the specimens stay in 7 and 28 days. For the 7 days old of specimens, the highest compressive strength has resulted from 50%:20% composition with the value of 5.88 N/mm2. For the 28 days old specimens, the highest compressive strength was 8.34 N/mm2. The lowest water absorption test was delivered by the more coal bottom ash in the composition of 40%:30%. It was 16.971%. The more coal bottom ash, the less water absorption. The mean of specimens density was 1.076 gr/cm3. The result of the research shows that recycles HDPE and coal bottom ash as concrete block meet the required strength.

Dissimilar welding of aluminum is an innovation used to increase the effectiveness and efficiency in making a product or component. It has been applied on the automotive industry, aerospace, and shipbuilding. Aluminum has low weldability in compared with steel material because of the oxide layer on the surface of aluminum. The welding problems of aluminum can be overcome by using a solid state welding such as friction stir welding (FSW). The objective of this study was to determine the strength of the welding joint and the microstructure of dissimilar welding joint with different series of aluminum. The tensile testing was performed with the weld directions of 0° and 45° to assess the formability, hardness testing, and microstructure of FSW. In this study, welding process was conducted to combine aluminum 1100 series (low strength aluminum) and aluminum 6061-T6 series (high strength aluminum) in the 2 mm thickness of aluminum sheet. The analysis was done by making comparison of the strength between dissimilar and similar aluminum series. The results showed that the dissimilar weld types, both in angle orientation of 0° and of 45° had fracture location on the HAZ area of 1100 aluminum series. The highest results of tensile strength were 78.07 MPa and 75.26 MPa for weld angle orientation of 0° and 45°, respectively. Weld angle orientation had significant effect to the strain where value of the welding direction of 0° was 10.99% and of 45° was 13.8%. Hardness test in the weld zone generated diverse values because the material stirring was not homogenous, whereas the similar welding was more stable in the welding area. Microstructure investigation on the dissimilar aluminum welding found a hook defects in the weld nugget. In the HAZ area, the grain size of 6061-T6 increased while of 1100 material decreased. It might be affected by the temperature and the aluminum characteristic. Meanwhile, in weld nugget, the grain size increased due to the stirring tool joint and heating during the welding process.

The objective on this research is to investigate the influence of tool rotation to the welding strength of Aluminium and Steel. AA1100 and ST37 were material selected for the specimens. The welding process was conducted by using Friction Stir Welding (FSW) method. The tensile strength and hardness of the specimens will be indicators of welding strength. FSW was carried out by using conventional milling machine with tool rotation of 800 rpm and 1250 rpm. Feed rate 10 mm/minute for all process. The tool tilt angle was 1° and 1.8 mm of depth plunge. By using 800 rpm, the average of Tensile Stress was delivered of 82.22 MPa and Strain of 1.09%. While for the use of 1250 rpm, Tensile Stress given 96.23 MPa and Strain 1.14%. The hardnes of HVN on the weld zone was 42.2 and 56.2 HVN for rotation of 800 and 1250 rpm respectively. Based on the Tensile Stress and the Hardness of the weld zone, the FSW process was influenced by tool rotation. The higher rotation given higher Tensile strength.

The objective on the research was to investigate the mechanical properties and microstructure of tailor welded blank (TWB) made from AA6061-T6 and AA1100 using friction stir welding (FSW) process. Due to the dissimilar mechanical properties of the two aluminium alloys, microhardness test was conducted to measure the hardness distribution across the weld nugget. The mixing of two distinct materials was influenced by tool rotation speed. Therefore, microstructure analysis was carried out to investigate the grain size and shape. The grain size of AA6061-T6 has increased in the heat affected zone (HAZ) while for AA1100 has decreased. In the weld nugget, it has found a hook defects in the dissimilar aluminium joining. By using monotonic tensile load, the different weld line direction was observed with the expansion in tool rotation. The joints failure were consistently on the area of AA1100 series. Furthermore, two specimens were investigated, one through the dissimilar aluminium and the other through similiar material. Inspection of the weld nugget hardness was shown that nonhomogen material intermixing during the stiring process as confirmed by microhardness measurement.