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S45C carbon steel is widely used as a raw material for tools and automotive components. In machine components, a material that has hard and ductile properties is also needed, with this problem, of course, it is necessary to have material engineering to improve the mechanical properties of steel in order to obtain good quality. The heat treatment process on the material has the advantage of improving mechanical properties. The purpose of this study was to determine the effect of heat treatment and shot peening on the mechanical properties and microstructure of the S45C carbon steel surface. S45C carbon steel was heat-treated at 900 oC and held for 15 minutes, then quenched using oil media. Next, the shot peening process was carried out with pressure variations of 4, 5, 6, and 7 bar for 20 minutes. Hardness testing was carried out using micro Vickers with a load of 0.49 N for 10 seconds. The results of the heat treatment on S45C material experienced an increase in hardness of 251.56 VHN compared to non-treatment, namely 187.38 VHN. Specimens that have been heated treated and shot peening with pressure variations of 4, 5, 6, and 7 bar experienced an increase in hardness of 286.18, 289.22, 357.24, and 450.22 VHN. The microstructure of the heat treatment material is formed by the phases of ferrite, pearlite, and martensite. The pearlite structure is denser and denser, showing increased hardness compared to non-treated S45C. Furthermore, the cross-sectional microstructure shows the depth of the shot peening effect as far as 130 μm. The surface of the specimen has a denser structure than the raw material.

AISI 304 is widely used as biomedical material due to its lower cost and availability, but low corrosion resistance. The shot peening method can increase the mechanical characteristics and corrosion resistance of a surface. The purpose of this study was to determine the effect of shot peening surface treatment with a combination of steel ball diameter variations and pressure on corrosion resistance of AISI 304 material. Shot peening treatment was carried out using variations of 0.2, 0.5, and 0.8 mm steel ball diameters with a hardness of around 40-50 HRC. Shot peening pressure varies from 7, 8, and 9 bar. Corrosion rate testing was carried out using bovine serum media. The results showed that the best increase in corrosion resistance was 0.117 mpy for a steel ball diameter of 0.5 mm with a pressure of 9 bar, 3 times lower than that of non-treated specimens, which was 0.378 mpy.

Aluminum is a lightweight material that is commonly used in engine components. However, aluminum's low hardness and wear resistance, requires special treatment before being used as a component. Increasing the hardness and wear resistance of aluminum can be done by coating Titanium Nitride (TiN) with the sputtering method. In this study, the effect of sputtering time on Al-TiN coating on hardness and wear resistance was obtained. The deposition of titanium nitride thin films on aluminum using a gas ratio of Ar: N ((70:30%) with varied treatment times of 30, 60, 90, and 120 minutes. Hardness and wear resistance were observed using Vickers hardness tester and Ogoshi High-Speed Universal. Whereas the morphology of the wear surface was observed by SEM. The result shows that the treatment time of 60 minutes obtained the highest hardness and minimum specific wear rate.

This study investigated the effect of adding strontium (Sr)-doped cobalt ferrite (CoFe2O4) nanoparticles in carbonyl iron particle (CIP)-based magnetorheological fluids (MRFs). Sr-CoFe2O4 nanoparticles were fabricated at different particle sizes using co-precipitation at calcination temperatures of 300 and 400 °C. Field emission scanning electron microscopy (FESEM) was used to evaluate the morphology of the Sr-CoFe2O4 nanoparticles, which were found to be spherical. The average grain sizes were 71–91 nm and 118–157 nm for nanoparticles that had been calcinated at 300 and 400 °C, respectively. As such, higher calcination temperatures were found to produce larger-sized Sr-CoFe2O4 nanoparticles. To investigate the rheological effects that Sr-CoFe2O4 nanoparticles have on CIP-based MRF, three MRF samples were prepared: (1) CIP-based MRF without nanoparticle additives (CIP-based MRF), (2) CIP-based MRF with Sr-CoFe2O4 nanoparticles calcinated at 300 °C (MRF CIP+Sr-CoFe2O4-T300), and (3) CIP-based MRF with Sr-CoFe2O4 nanoparticles calcinated at 400 °C (MRF CIP+Sr-CoFe2O4-T400). The rheological properties of these MRF samples were then observed at room temperature using a rheometer with a parallel plate at a gap of 1 mm. Dispersion stability tests were also performed to determine the sedimentation ratio of the three CIP-based MRF samples.

AISI 304 is a type of stainless steel used for load bearing implants due to relatively low cost. However, its mechanical properties and corrosion resistance must be improved to the level of AISI 316L, cobalt-based alloys, titanium and titanium alloy properties. Its fatigue characteristic is also one of the most important criteria have to be evaluated to achieve the overall service performance requirements, when this material subjected to dynamic load. High surface hardness may delay fatigue crack initiation and decrease corrosion rate because these two processes initiated at surface layer. The purpose of this research is to investigate the change in mechanical and corrosion characteristics of AISI 304 due to shot peening processes.Surface treatment with shot peening process were done by regulating the variation time for 0, 5, 10, 20, 30 and 40 minutes at the firing pressure of 7 bar; using 0,6 mm steel ball with hardness of 40-50 HRC. Firing distance between the nozzle with the specimen surface is 100 mm. Surface hardness was tested using indentation load of 10 grams for 10 seconds. Pitting corrosion test of treated AISI304 and non treated AISI316L was conducted in intravenous Otsu-RL brands as corrosion media. Pitting corrosion was performed using cyclic polarization methodThe hardness of surface layer increase with increasing shot-peening time. According to increase of length of shot-peening time from 0, 5, 10, 20, 30 and 40 minutes the hardness of these specimen increase to 241, 404, 418, 437, 481 and 496 VHN, respectively. The pitting corrosion rate tend to significantly decrease with increasing of shot peening time. According to increase of length of shot peening time from 0, 5, 10, 20, 30 and 40 minutes the pitting corrosion rate of these specimen also decrease to 0.853, 0.619, 0.086, 0.017, 0.116 and 0.036 mpy, respectively. Pitting corrosion rate of AISI316L is 0.042 mpy. Best pitting corrosion rate of treated AISI304 is 2.5 times smaller than that of non treated AISI316L. Therefore, shot-peening could be used to increase hardness number and reduce pitting corrosion rate, significanly.