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Duplex Stainless Steel의 저온 플라즈마 침질탄화시 Pulse Frequency 및 Duty Factor에 따른 표면 특성평가
천창석(Chang-seok Cheon),이인섭(Insup Lee) 한국표면공학회 2014 한국표면공학회지 Vol.47 No.5
A low temperature plasma nitrocarburizng was implemented on the duplex stainless steel to achieve the enhancement of surface hardness without degradation of its corrosion resistance. Attempts were made to investigate the influence of Pulse frequency and Duty factor of pulsed power in a high Pulse frequency regime on the surface characteristics of the hardened layer. The hardened layer (S-phase) was formed on all of the treated surfaces. Surface hardness reached up to 1300 HV0.1 which is about 4.6 times higher than that of the untreated material (280 HV0.1). The thickness of the hardened layer tends to increase lightly with the higher Pulse frequency and the higher Duty factor. The corrosion resistance of nitrocarburized duplex stainless steel was almost similar to that of the untreated material. Both the Pulse frequency and the Duty factor do not have a significant influence on the corrosion property of plasma treated duplex stainless steel.
SDSS (Super Duplex Stainless Steel) 강관의 미세조직 및 부식특성에 미치는 열처리 온도의 영향
이인섭(Insup Lee),천창석(Chang-seok Cheon),임태홍(Tai-Hong Yim),한윤호(Yoon-Ho Han),이면학(Myon-Hag Lee) 한국표면공학회 2015 한국표면공학회지 Vol.48 No.6
The aim of this paper is to determine the proper heat treatment temperature for SDSS tube production without σ-phase precipitation. When Mother steel tube was heat treated at 800℃ temperature, relatively a large amount of σ-phase precipitated and grain refinement of ferrite phase occurred simultaneously. However, in Pilgered and Drawn steel tubes, grain refinement of the ferrite phase did not occur and a small amount of σ-phase precipitated. For all three types of steel tubes, the pitting potential was reduced to 2/5 or less compared with the untreated one and corrosion also occurred in the salt spray test due to the precipitation of σ-phase. When heat treatment temperature was 900℃, grain refinement of the ferrite phase occurred and very little σ-phase precipitated in Pilgered and Drawn steel tubes. But when heat treatment was done at 1,000℃ temperature, all three types of steel tubes had a similar corrosion properties of that of untreated one and also corrosion did not occur in the salt spray test, as σ-phase did not precipitate. Therefore, the optimum heat treatment temperature range is determined to be more than 1000℃ for the SDSS at which corrosion does not occur.