COCRMOW ALLOY DESIGN FOR BRAKE DISC APPLICATION USING THERMODYNAMIC CALCULATION AND FIRST-PRINCIPLES SIMULATION

• Main Author: Adinata, Daniel
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/72564
• Institution: Institut Teknologi Bandung

CoCrMoW is an alloy that is commonly used for biomedical applications, cutting tools, and brake disc. Brake disc is used for braking system through friction mechanism. CoCrMoW alloy used for brake disc application must have good mechanical properties at room and high temperatures during application to prevent wear and thermal fatigue. Cobalt-based material, specifically CoCrMoW, was used as research subject because of its high wear resistance, thermal resistance, low fatigue crack propagation rate, and corrosion resistance at high temperatures. The alloying elements (Ni, Fe, and Mn) are varied in the CoCrMoW alloy to obtain the optimal stacking fault energy (SFE) adjustment method to get the desired mechanical properties. A series of SFE simulations for CoCrMoW alloys have been carried out to study the effect of temperature and alloying element concentration on the SFE value of the alloy. Calculation of the effect of temperature on the value of SFE is carried out by thermodynamic calculations in the temperature range of 0-700 °C. The effect of the concentration of the alloying elements on the value of SFE through thermodynamic calculations is carried out at a concentration of 0-10 wt.%. In the first-principles method, calculations are carried out to determine the equilibrium lattice parameters of the CoCrMoW alloy which are used to calculate the SFE value of the alloy with various alloying elements. The effect of alloying element concentration and supercell structure on the electronic structure (charge density and density of states) of the CoCrMoW alloy was also simulated at 0 K using the first-principles method. The addition of alloying elements Ni, Fe, and Mn to the CoCrMoW alloy will increase the SFE value of the alloy from -0.09 J/m2 to -0.04 J/m2 using thermodynamic calculation method and from 0.07 J/m2 to 0.16 J/m2 using first-principles simulation. The difference in the SFE value of the thermodynamic calculation method and the first-principles simulation is in the range of 0.15-0.26 J/m2 because the SFE value of the FP-DFT simulation depends on the position of the alloying elements. In the CoCrMoW alloy, the addition of alloying elements Ni, Fe, and Mn strengthens the bonds between atoms in the CoCrMoW alloy which then affects the electronic structure (increases the charge density and DOS) so that the SFE value increases. Based on the analysis of SFE calculations and the effect of alloying elements to CoCrMoW alloy, the suggestion for the design of CoCrMoW alloy is to add Fe as the alloying element to adjust the SFE value more effectively up to 5 wt.% so that the alloy's ductility increases while still maintaining the fatigue resistance of the alloy.