HOT CORROSION BEHAVIOR IN COATING NiCr//NiCr [400 mesh] + Cr3C2 USING HVOF THERMAL SPRAY TECHNIQUE WITH SUBSTRATE STAINLESS STEEL 304

• Main Author: WIRAWAN - NIM : 12514054 , ADI
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/25043
• Institution: Institut Teknologi Bandung

<p align="justify">Population growth causes the need for electrical energy continues to increase. Coal-fired power plant is still widely used because it uses relatively cheap fuel. Burning coal produces greenhouse gases that can cause climate change. Therefore, it is necessary to increase the efficiency of the power plant so that more electricity is produced with the same fuel as before or even less than before. To increase the efficiency of the steam power plant, it is necessary to increase the temperature and pressure of the steam operation. Therefore, strong material required at high temperature, oxidation resistance and heat corrosion resistance. In this study, NiCr//NiCr (400 mesh) + Cr3C2 hot corrosion coating analysis was performed using the method of dyeing the specimen into saline solution and giving hot corrosion treatment in order to test the specimen resistance to hot corrosion attack and to study the effect of NaCl and Na2SO4 salt on hot corrosion that happened. <br /> <br /> A series of experiments were conducted to study the resistance of hot corrosion coating of NiCr//NiCr[400 mesh] + Cr3C2 was coated using HVOF technique on 304 stainless steel substrate with the variation of NaCl and Na2SO4 salt at 750oC. The test was performed using muffle furnace with %mole of Na2SO4/NaCl salt (100/0; 66/33; 33/66; 0/100) and time variation 5 hours and 50 hours at temperature 750oC. After testing, the high temperature corrosion product compound was be identified using X-Ray Diffraction (XRD) and the formed oxide thickness, pitting, spalling and specimen morphology identified using Scanning Electron Microscope - Energy Dispersion Spectrometry (SEM-EDX). <br /> <br /> Hot corrosion type II occurs in specimens with variations of % mole of Na2SO4 / NaCl salt (66/33, 33/66 and 0/100) as there is pitting on the specimen. The highest oxide thickness was 18.63 &#956;m and the deepest pitting was 25,33 um occurring on a 100% NaCl specimen with hot corrosion treatment for 50 hrs. Increased levels of NaCl in salt variations result in an increase in oxide thickening rate on the surface of the specimen because Cl2 gas can catalyze the oxidation of Cr. Oxides formed on the surface of the specimens are Cr2O3 and NiO oxides and no spinel and Cr3C2 are detected. Decarburization of Cr3C2 occurs in each specimen so that Cr3C2 loses carbon and oxidizes to Cr2O3. There is spalling on each specimen because the Cr2O3 Pilling-Bedworth Ratio (PBR) is 2.07 and the sulfur element and Cl2 can be segregated to the metal-oxide interface thus weakening the oxide bond with the metal.<p align="justify">