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STS 347 및 STS 310S 오스테나이트계 스테인리스강의 고온질화
공정현(J .H. Kong),박준홍(J. H. Park),김영희(Y.H. Kim),성장현(J. H. Sung) 한국기계가공학회 2008 한국기계가공학회 춘추계학술대회 논문집 Vol.2008 No.-
High Temperature Gas Nitriding(HTGN) of STS 347 and STS 310S austenitic stainless steels has been investigated in an atmosphere of nitrogen gas at the temperature range between 1050 ℃ and 1150℃. The phase change, the hardness variation, precipitates, the nitrogen content and the corrosion resistance of the HTGN treated steels were examined. The surface layer of 347 austenitic stainless steel appeared the nitrides of rod type and round type, and fine precipitates were observed in the austenite, while the surface layer of STS 310S autenitic stainless steel appeared nitrogen pearlite, which was composed of Cr2N and austenite alternatively, at the outermost surface layer. The surface hardness of STS 347 showed 250~370Hv, depending on the HTGN conditions, while the interior austenite phase represented ~175Hv. The surface hardness of STS 310S showed 270~410Hv, while the interior austenite phase region represented 160Hv. The nitrogen content was analyzed 1.4% and 1.6%, respectively, at the surface layer of STS 347 and STS 310S steels. For both STS 347 and 310S austenitic stainless steel, the corrosion resistance of nitrogen permeated steels were superior to that of solution annealed steels.
13%Cr-0.17%C 스테인리스강의 고온 가스질화에 미치는 Al 함량 변화의 영향
박범태 ( B. T. Park ),김정민 ( J. M. Kim ),강희재 ( H. J. Kang ),공정현 ( J. H. Kong ),강창룡 ( C. Y. Kang ),성장현 ( J. H. Sung ) 한국열처리공학회 2011 熱處理工學會誌 Vol.24 No.6
This study has been performed to investigate the effect of Al addition on High Temperature Gas Nitriding (HTGN) in 13%Cr-0.16%C stainless steel with different Al contents of 0.54%, 1.76% and 2.36%, respectively. HTGN treatment was carried out at 1100°C for 1 hr, 5 hrs and 10 hrs. Nitrogen-permeated surface layers showed round type carbides of Cr23C6 and needle type nitrides of AIN in the matrix of martensite, representing 600-700 Hv. And the thickness of the surface layer increased with increasing Al content and HTGN treatment time. The inner region that was not permeated nitrogen showed chromium carbides in the mixed phase of martensite and ferrite for the 0.53% Al alloyed steel, however chromium carbides in the matrix of ferrite single phase were shown for the steels with the addition of 1 .76%Al and 2.36%Al, representing the hardness of ~200 Hv. During nitrogen permeation from surface to the interior, substitutional elements of Cr, Al and Si moved toward the surface and interstitial element of carbon also moved from interior to the surface. This movement of alloying elements leads high concentration of these elements at the outmost surface, subsequently the lowest peak of substitutional elements were shown in the vicinity of near surface. After showing the lowest peak, the high concentration region of Al and C were formed due to the continuous movement of Al toward the surface. The long discontinuous precipitates of Cr23C6 and AIN were formed along the outmost surface owing to the high concentration of these alloying elements. (Received August 30, 2011; Revised September 15, 2011; Accepted October 4, 2011)