Preprint Article Version 1 This version is not peer-reviewed

The Effect of C2H2/H2 Gas Mixture Ratio in Direct Low-Temperature Vacuum Carburization

Version 1 : Received: 29 May 2018 / Approved: 30 May 2018 / Online: 30 May 2018 (06:23:47 CEST)

A peer-reviewed article of this Preprint also exists.

Song, Y.; Kim, J.-H.; Kim, K.-S.; Kim, S.; Song, P.K. Effect of C2H2/H2 Gas Mixture Ratio in Direct Low-Temperature Vacuum Carburization. Metals 2018, 8, 493. Song, Y.; Kim, J.-H.; Kim, K.-S.; Kim, S.; Song, P.K. Effect of C2H2/H2 Gas Mixture Ratio in Direct Low-Temperature Vacuum Carburization. Metals 2018, 8, 493.

Journal reference: Metals 2018, 8, 493
DOI: 10.3390/met8070493

Abstract

The effect of the acetylene and hydrogen gases mixture ratios in direct low-temperature vacuum carburization was investigated. The gas ratio is an important parameter for producing the free radicals in the carburization. The free radicals can remove the natural oxide film by the strong reaction of the hydrocarbons, and then thermodynamically activity can be increased. When the gas ratio was below 1, the supersaturation expanded austenite layers were formed on the surface of the AISI 316L stainless steel, which had the maximum carbon solubility up to 11.5 at.% at 743 K, were formed. On the other hand, when the gas ratio was above 1, the carbon concentration of them remained low even if the process time was enough increased to reach the maximum carbon solubility. As a result, the carbon concentration underneath the surface was determined to be highly dependent on the gas mixture ratio of acetylene and hydrogen. In conclusion, it is necessary to restrict the ratio of acetylene and hydrogen gases to total mixture gases to form the expanded austenite layer with the high carbon concentration in the direct low-temperature vacuum carburization.

Subject Areas

direct surface activation; low-temperature vacuum carburization; expanded austenite; supersaturation; acetylene