Oct, 31, 2024

Vol.57 No.5

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  • The Korean Society of Surface Science and Engineering
  • Volume 56(1); 2023
  • Article

Review

The Korean Society of Surface Science and Engineering 2023;56(1):94-103. Published online: Feb, 28, 2023

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DOI : 10.5695/JSSE.2023.56.1.94

Effect of process pressure and nitrogen addition ratio on the uniformity of hardening depth and surface properties of Cr-Mo low alloy steel in vacuum carburizing

  • Gi-hoon Kwona,b, Hyunjun Parka, Young-Kook Leeb, Kyoungil Moona,*
    aHeat & Surface Technology R&D Group, Korea Institute of Industrial Technology, Siheung, 15014,Korea, bDepartment of Materials Science and Engineering, Yonsei University, Korea
Abstract

The effects of carburizing pressure and gas ratio on vacuum carburizing properties (uniformity and surface characteristics) have been studied through the analyses of carbon concentration, hardness, surface color, surface roughness and type of carbon bonding. AISI 4115 steel specimens were carburized with various pressures (1, 5, and 10 Torr) at different locations (P1, P2, P3, P4, P5, and P6) inside a furnace held at 950 ℃. Since the carburizing pressure represents the density of the carburizing gas, it plays an important role in improving the carburizing uniformity according to locations in the furnace. As the carburizing pressure increased, the carburizing uniformity according to the sample location was improved, but the surface of the carburized specimen was discolored due to the residual acetylene gas, which does not contribute to the carburizing reaction. Therefore, the carburizing uniformity and surface discoloration have been improved by injecting acetylene gas (carburizing gas) and nitrogen gas (non-reactive gas) in a specific ratio.

Keywords Vacuum carburizing; Pressure; Uniformity; Acetylene; Nitrogen.