In this study, evolution of microstructural, hardness value, and dimensional crosshead valve that has been welded with Ni-Cr-B-Si-C alloys deposit are investigated. Ni-Cr-B-Si-C alloys has deposited to replace nickel alloys on component that have wear. The process that used is GTAW welding process with variation of amperes and with or without using water backing technique. Result from this study, on weld metal microstructure with variation of heat input and water backing method made same structure like original materials. On base metal microstructure, resulting same structrue as original material that consist of ferrite and pearlite. However, on HAZ which used 140 A on welding current and water backing method produced martensite structure. The greater heat input make a greater hardness value on weld metal and water backing can keep the original hardness from material. In addition, heat input and water backing that used in this processs not cause a deformation on crosshead components result from dimensional test which still suitable with original component specification.
Pack carburizing is one method of adding carbon into the steel surface. This method is done to improve the mechanical properties of steel so as to reduce the risk of material failure due to static and dynamic load. It has been done in this research about pack carburizing with mixed bintaro charcoal media with coconut shell on ST 41 steel. Carburizing method is done by heating steel which is given a mixture of charcoal at 900 celsius temperature with variation of holding time (1h, 1.5h, 2h) And variation of the charcoal mix ratio with BaCO3 (90: 10, 85: 15, 80: 20). Conducted testing of microstructure, jominy, and the composition so it is known that the mixture of bintaro charcoal and coconut shell quite effectively used as a media pack carburizing. It can be seen that the hardness value of carbon steel has increased with the highest value of 65 HRC, metallographic test results showed good carburizing coating with the best thickness value of 30.9 µm, in jominy testing showed the low hardness carbon steel ability increased with the highest distance from the specimen quench-ends about ¾ inch and on the compositional test results showed an increase in carbon content in steel more than 200%.
Abstract.This research studied the inhibition of corrosion by bawang dayak leaves extract (EleutherineamericanaMerr.) on API 5L steel in brine water environment (3.5% NaCl). The inhibitor was extracted using maceration process from bawang dayak leaves that was cultivated in Paser District, East Kalimantan. The test of antioxidant activity showed that bawang dayak leaves extract is a very powerful antioxidant with IC 50 value of 27.30204. The results from FTIR test show the presence of electronegative atoms and double bonds of the alkenes groups that provide the potential of the extract as a corrosion inhibitor. Efficiency of inhibition reached up to 93.158% for the addition of inhibitor with 300 ppm concentration and 20 days of immersion time. This inhibitory behavior is also supported by polarization measurements where the lowest corrosion rate of 0.00128 mm/year is obtained at the same concentration and immersion time.
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