• 한국재료학회지
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• 제12권5호
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• pp.414-422
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• 2002

Three different multi-component white cast irons alloyed with Cr, V, Mo and W were prepared in order to study their as-cast and solidification structures. Three combinations of the alloying elements were selected so as to obtain the different types of carbides and matrix structures : 3%C-10%Cr-5%Mo-5%W(alloy No.1), 3%C-10%V-5% Mo-5%W(alloy No. 2) and 3%C-17%Cr-3% V(alloy No.3). The as-cast microstructures were investigated with optical and scanning electron microscopes. There existed two different types of carbides, $M_7C_3$ carbide with rod-like morphology and $M_6C$ carbide with fishbone-like one, and matrix in the alloy No. 1. The alloy No. 2 consisted of MC carbide with chunky and flaky type and needle-like $M_2C$ carbide, and matrix. The chunky type referred to primary MC carbide and the flaky one to eutectic MC carbide. The morphology of the alloy No. 3 represented a typical hypo-eutectic high chromium white cast iron composed of rod-like $M_7C_3$ carbide which is very sensitive to heat flow direction and matrix. To clarify the solidification sequence, each iron(50g) was remelted at 1723K in an alumina crucible using a silicon carbide resistance furnace under argon atmosphere. The molten iron was cooled at the rate of 10K/min and quenched into water at several temperatures during thermal analysis. The solidification structures of the specimen were found to consist of austenite dendrite(${\gamma}$), $ ({\gamma}+ M_7C_3)$ eutectic and $({\gamma}+ M_6C)$ eutectic in the alloy No. 1, proeutectic MC, austenite dendrite(${\gamma}$), (${\gamma}$+MC) eutectic and $({\gamma}+ M_2C)$ eutectic in the alloy No. 2, and proeutectic $M_7C_3$ and $ ({\gamma}+ M_7C_3)$ eutectic in the alloy No 3. respectively.

• 한국재료학회지
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• 제11권6호
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• pp.472-476
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• 2001

광학 및 주사전자현미경을 사용하여 X%C-5%Cr-5%V-5%Mo-5%W-5%Co 조성을 가진 다합금계백주철에서 정출되는 탄화물의 종류 및 형태를 3차원적으로 관찰하였는 바 MC, M$_2$C 및 M$_{7}$C$_{3}$의 3종류의 탄화물이 정출되었다. MC탄화물은 꽃잎, 구상 그리고 산호초형태의 3종류, M$_2$C탄화물은 층상 및 판상의 2종류, M$_{7}$C$_{3}$7탄화물은 고크롬백주철에서 관찰되는 막대형태의 한 종류만 관찰되었다. 첨가한 합금원소중 Co는 기지조직에만 고용되었기 때문에 탄화물의 현상에는 영향을 미치지 않았다.않았다.

• Journal of Welding and Joining
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• 제15권1호
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• pp.101-108
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• 1997

손상된 터어빈 로터강의 보수 용접에 있어서 용접부의 크립 파단 수명과 탄화물간의 관계가 연구되었다. 탄화물은 탄화물 추출 복제법을 이용하여 확인되었으며 로터강에는 Molybdenum 주성분의$M_2C$, Vanadium 주성분의 $M_4C_3$, 및 Chromium 주성분의 $M_{23}C_6$와 $M_7C_3$ 탄화물이 존재하였다. 한편 ICHAZ에서 파단된 시험편의 파단면에서는 구상의 조대한 Molybdenum 주성분의 $M_6C$ 탄화물이 발견되었다. 조대한 Molybdenum 주성분의 $M_6C$ 탄화물의 석출은 탄화물 주위에 고용경화 원소인 Molybdenum 농도를 떨어뜨려 기공 발생 원인을 제공하였다. CGHAZ에서 파단된 용접부의 파단면에서는 조대한 $M_6C$ 와 $M_{23}C_6$가 발견되었다.

• 한국표면공학회지
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• 제22권1호
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• pp.10-16
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• 1989

The properties of carburization on Fe-Cr alloys at 900-96$0^{\circ}C$were investiged. The study on carbide layer which had developed during solid-carburizing was made by use of S.E.M, E.PM.A, and X-ray analyzer. The results obtained were summarized as follows, the composition of carbide and the value of activation energy for the growth of carbide layer on each Fe-Cr alloy were 1) Fe-1Cr : M3C and 52Kcal/mole 2) Fe-3Cr and Fe-5Cr : M7C3and 85-88Kcal/mole 3) Fe-7Cr and Fe-9Cr : (M7C3+M23C6)and 55-66Kcal/mole.

• 기술사
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• 제21권1호
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• pp.5-12
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• 1988

The purpose of this paper is to investigate on the optimum coating thickness layer of TiC-Al$_2$O$_3$ coated cemented carbide tool. Chemical Vapor Deposition (CVD) of a thick film of TiC-A1$_2$O$_3$ on a cemented carbide produces an intermediate layer, $1.5mutextrm{m}$, 4.5${\mu}{\textrm}{m}$, 7.5${\mu}{\textrm}{m}$ 10.5${\mu}{\textrm}{m}$, 4 kind of TiC between the substrate and the $1.5mutextrm{m}$ constant thick A1$_2$O$_3$ coating. Experiments were carried out with the test relationship between coating thickness and shear angle, surface roughness, cutting force, microphotograph of crater wear, flank wear, tool life. From the experimental results, it was found that the optimum coating thickness of TiC-A1$_2$O$_3$ is 6${\mu}{\textrm}{m}$. Although the coating thickness layer 9${\mu}{\textrm}{m}$. 12${\mu}{\textrm}{m}$ have a much loger tool wear than an 3${\mu}{\textrm}{m}$, 6${\mu}{\textrm}{m}$ coating tool in cutting condition feed 0.05mm/rev, and the condition of feed 0.2mm/rev, 0.3mm/rev has upon in the shot time phenomenon of chipping.

• 열처리공학회지
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• 제30권5호
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• pp.197-206
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• 2017

The microstructure of a high-carbon and high-chromium cast steel (HK700) for cold-work die inserts was analyzed by advanced scanning electron microscopy. A continuous network of primary $M_7C_3$ carbide was developed among austenitic matrix after casting. A small amount of $M_2C$ was added to the carbide network owing to the enrichment of Mo and W during the solidification. After quenching in which the austenitization was performed at $1030^{\circ}C$ and double tempering at $520^{\circ}C$, the network structure of $M_7C_3$ was preserved while most of the matrix was transformed to martensite because of additional carbide precipitation. The $M_2C$ in the as-cast microstructure was also transformed to $M_6C$ due to its instability. The continuous network of coarse carbides owing to the absence of hot-working had little influence on the hardness after quenching and tempering, whereas it resulted in severe brittleness upon flexural loading.

• 한국주조공학회지
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• 제20권5호
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• pp.323-329
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• 2000

The HSS consists of hard carbide and matrix of martensite, and so its characteristics of wear resistance, fracture resistance, and surface roughness are good. This study was undertaken to investigate the influence of Nb and V and manufacturing conditions on microstructural behaviors and characteristics in the HSS cylindrical specimens(90 $mm^{O.D.}$ ${\times}$ 60 $mm^{I.D.}$ ${\times}$ 50 $mm^H$) manufactured using VCC(Vertical Centrifugal Casting). In the specimen of Fe-2C-6Cr-1.5W-3Mo-4V alloy, the amount of MC carbide was increased and $M_7C_3$ carbide was decreased with the increase of V and Nb contents. The primary VC carbide was formed and followed by the rod-type eutectic MC carbide was formed in the cell boundary in 9%V added specimen. MC carbide was increased, and $M_7C_3$ carbide was decreased with the addition of Nb content. In the specimen containing more than 3%Nb, primary NbC carbide was formed within the cell of matrix. With increase in rpm, cell and carbides became fine, and amount of carbide $M_7C_3$ was decreased due to increase in cooling rate.

• 대한금속재료학회지
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• 제48권7호
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• pp.589-597
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• 2010

In the present study, the effect of variation in alloying elements on the carbide formation behavior during casting and homogenization treatment of M2 high speed steels was investigated. M2 high speed steels of various compositions were produced by vacuum induction melting. Contents of C, Cr, W, Mo, and V were varied from the basic composition of 0.8C, 0.3Si, 0.2Mn, 4.0Cr, 6.0W, 5.0Mo, and 2.0V in weight percent. Homogenization treatment at $1150^{\circ}C$ for 1.5 hr followed by furnace cooling was performed on the ingots. Area fraction and chemical compositions of eutectic carbide in as-cast and homogenized ingots were analyzed. Area fraction of eutectic carbide appeared to be higher in the ingots with higher contents of alloying elements the area fraction of eutectic carbide also appeared to be higher on the surface regions than in the center regions of ingots. As a result of the homogenization treatment, $M_2C$ carbide, which was the primary eutectic carbide in the as-cast ingots, decomposed into thermodynamically stable carbides, MC and $M_6C$. The latter carbide was found to be the main one after homogenization. Fine carbides uniformly distributed in the matrix was found to be MC type carbide and coarsened by homogenization.

• 한국재료학회지
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• 제7권4호
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• pp.310-316
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• 1997

The effects of carbide and matrix structures on the abrasion wear resistance of multi-component white cast irons with 3.0 mass%C have been studied in this paper. Four different heats were poured in order to obtain the specimens with different combinations of the carbide structures: a basic iron(3.0 mass%C-5.0 mass%Cr-5.0 mass%V-5.0 mass% Mo-12.5mass%W)for M$_{6}$C and M$_{7}$C$_{3}$ carbides, and a Cr free iron(3.0 mass%C-5.0 mass%V-2.5mass%Mo-12.5 mass%W) for MC and M6C carbides. A conventional high Cr free free iron(3.0 mass%C-5.0 mass%V-2.5 mass%Mo-12.5 mass%W) for MC and M6C carbides. A conventional high Cr white cast iron was also poured to compare its wear resistance with those of the multi-component white cast irons. In the as-cast condition, the range of abrasive wear rate(Rw=mg/min) was from 4.15 to 5.98 . The lowest Rw, which means the highest wear resistance, was obtained in the basic iron with nodular MC, lamellar M$_{2}$C and cellular M$_{7}$C$_{3}$ carbides. On the other hand, the Rw of the high Cr white cast iron ranked between the basic iron and the Mo and W free iron. In each alloy, the Rw of air hardened or tempered specimen was lower than that of the as-cast one because of the change of matrix structures by the heat treatments. The Rw of the hear treated speci-mens increased in the order Mo and W free iron, basic iron, Cr free iron, high Cr iron, and V free iron.n.n.n.

• 열처리공학회지
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• 제5권2호
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• pp.111-121
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• 1992

For the purpose of investigating the effect of austenitizing temperatures on the mechanical properties of 0.23% C-13.6%Cr martensitic stainless steel, tensile properties, hardness, impact value and carbide extraction were examined after changing the austenitizing temperatures and tempering temperatures. The results obtained are summerized as follows. The carbide laminations formed from hot rolling before austenitization could not be eliminated after austenitizing at $950^{\circ}C$. With increasing austenitizing temperature, hardness increased and showed maximum value at $1050^{\circ}C$ and then slightly decreased. With increasing tempering temperature up to $500^{\circ}C$, impact value and elongation appeard to be decreased but hardness showed nearly unchanged at austenitizing temperature of $1150^{\circ}C$ due to the fine $M_7C_3$ carbides precipitation. The abrupt increase in impact value, hardness and elongation above the tempering temperature of $500^{\circ}C$ appeared to change in carbide structure from fine $M_7C_3$ to coarse $M_{23}C_6$.