Enhancing the Hardness of Sintered SS 17-4PH Using Nitriding Process for Bracket Orthodontic Application

International Conference on Chemistry and Material Science 2017

化学;材料科学

Suharno, B.^1 ; Supriadi, S.^2 ; Ayuningtyas, S.T.^1 ; Widjaya, T.^1 ; Baek, E.R.^3

Metallurgy and Materials Engineering Department, University of Indonesia, Depok, Indonesia^1

Mechanical Engineering Department, University of Indonesia, Depok, Indonesia^2

School of Materials Science and Engineering, Yeungnam University, Korea, Republic of^3

关键词: Gaseous nitriding;    Material hardness;    Nitriding process;    Nitriding treatment;    Optical metallography;    Precipitation process;    Solid solution phase;    Vickers microhardness tester;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/299/1/012050/pdf
DOI  :  10.1088/1757-899X/299/1/012050

学科分类：材料科学（综合）

来源: IOP

【 摘 要 】

Brackets orthodontic create teeth movement by applying force from wire to bracket then transferred to teeth. However, emergence of friction between brackets and wires reduces load for teeth movement towards desired area. In order to overcome these problem, surface treatment like nitriding chosen as a process which could escalate efficiency of transferred force by improving material hardness since hard materials have low friction levels. This work investigated nitriding treatment to form nitride layer which affecting hardness of sintered SS 17-4PH. The nitride layers produced after nitriding process at various temperature i.e. 470°C, 500°C, 530°C with 8hr holding time under 50% NH3atmosphere. Optical metallography was conducted to compare microstructure of base and surface metal while the increasing of surface hardness then observed using vickers microhardness tester. Hardened surface layer was obtained after gaseous nitriding process because of nitride layer that contains Fe4N, CrN and Fe-αN formed. Hardness layers can achieved value 1051 HV associated with varies thickness from 53 to 119 μm. The presence of a precipitation process occurring in conjunction with nitriding process can lead to a decrease in hardness due to nitrogen content diminishing in solid solution phase. This problem causes weakening of nitrogen expansion in martensite lattice.