• Proceedings of the Korean Nuclear Society Conference
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• 1995.05b
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• pp.623-628
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• 1995

여러 가지 Zr합금에 대한 부식시험을 autoclave를 이용하여 물과 여러 가지 Li 용액에서 수행하였다. 합금은 11종의 신합금을 사용하였는데 크게 나누어 Zircaloy형 합금(ZrSnFeCr), ZrNbFeCr, ZrSnNbFeCr과 ZrFeCr 합금으로 대별되며, 비교평가를 위해 표준 Zircaloy-4 합금에 대해서도 부식시험을 수행하였다. 모든 합금에서 Li을 일정농도이상 첨가할 때 부식은 가속되는데, 부식은 Li의 농도가 2.2와 30 ppm 사이일 때 가속되기 시작한다. Li은 부식거동에 있어서 천이후 영역에서의 부식속도 보다는 천이시간과 무게 증가량에 더 영향을 끼치는 것으로 나타났다. 수소흡수율은 Li 농도와 합금에 따라서 강하게 영향을 받는 것으로 나타났으며, Li 농도가 30 ppm 이상에서는 Li 가속부식과 함께 Li가속 수소흡수현상이 나타났다. ZrSnFeCr합금들은 낮은 부식속도와 늦은 천이현상을 보이며 표준 Zircaloy보다 훨씬 우수한 부식저항성을 보인 반면에, 대부분의 Nb첨가 합금은 높은 부식속도와 빠른 천이 현상을 보였다.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.282-285
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• 2009

Selective laser sintering (SLS) is a fast growing process of rapid production fur metallic based parts. To restore damaged mold surface using SLS, single layer experiments of $20{\mu}m$ Fe-Cr powder was performed under various heat input. Process window of $20{\mu}m$ Fe-Cr powder provided feasible process parameters for the smooth regular surface. To estimate coherence between melted powder and basematal, tendency of hardness distribution has been observed. Hardness of melted zone and remelted zone was diversified from 5GPa to 6.5GPa. It is over 2 times compared of hardness of basemetal. Average surface roughness of each direction on surface of melted powder was measured. Experimental results show that the mold restoring process using SLS can be successfully applied in the mold repair industry.

• Journal of the Korean institute of surface engineering
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• v.29 no.1
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• pp.36-44
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• 1996

Fe-Cr-Al and Fe-Cr-Al-Hf alloys prepared either by arc melting or by single roll casting(melt spinning) were exposed to air isothermally at 900~$1100^{\circ}C$. Whisker-like alumina was observed on the surface of the specimens when oxidized at $900^{\circ}C$, but convoluted alumina above $1000^{\circ}C$. All the Hf-free specimens and Hf-added specimens produced by single roll casting formed only external scale mainly composed of $Al_2O_3$ after oxidation at 900~$1100^{\circ}C$ for 100 hours, but Hf-added specimen produced by arc melting formed Hf-rich internal oxides below the thin external $Al_2O_3$ scale except at $900^{\circ}C$. Most of the rapidly solidified Fe-Cr-Al alloys showed smaller weight gains than conventionally casted ones besides Hf-added one oxidized at $1100^{\circ}C$.

• Korean Journal of Materials Research
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• v.14 no.1
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• pp.52-58
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• 2004

The surface property and formation behavior of a boride layer formed on Ni-Cr-Mo steel in a plasma paste boronizing treatment were investigated. The plasma paste boronizing treatment was carried out at 973～1273 K for 1-7 hrs under the gas ratio of Ar:H$_2$ (2:1). The thickness of the boride layer increased with increasing temperature and time in the boronizing treatment. The cross-section of the boride layer was a tooth structure and the hardness was Hv 2000～2500. XRD analysis revealed that the compound was identified as FeB, $Fe_2$B, and mixed phase of FeB/$Fe_2$B in the boride layer formed at 973～1073 K, 1173K, and 1273K, respectively. The Ni-Cr-Mo alloy boronized at 1173-1273 K showed the best excellent wear resistance against the sand. As a results of corrosion test in 1 M $H_2$$SO_4$ solution, $Fe_2$B formed on the matrix alloy exhibited higher corrosion resistance than FeB.

• Journal of the Korean institute of surface engineering
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• v.49 no.2
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• pp.147-151
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• 2016

The T91 steel (Fe-9%Cr-1%Mo) was corroded at 600 and $700^{\circ}C$ for 5 - 70 h in the $N_2$/(0.5, 2.5)%$H_2$Smixed gas at one atm. It was corroded fast, forming the outer FeS layer and the inner (FeS, $FeCr_2O_4$)-mixed layer. The formation of the outer FeS layer facilitated the oxidation of Cr to $FeCr_2O_4$ in the inner layer. Since the nonprotective FeS scale was present over the whole scale, T91 steel displayed poor corrosion resistance.

• Journal of the Korean institute of surface engineering
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• v.37 no.1
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• pp.28-39
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• 2004

The effect of trace metallic additives on microstructure, surface appearance and hardness of zinc electrodeposits was investigated by using sulfate bath and flow cell system. The preferred orientation of Zn deposit with Fe additive was (103)(104)+(002) mixed texture and that of Zn deposits with both Fe-Ni and Fe-Co additives was (10 1), while Zn deposits with Fe-Cr additives had (002) preferred orientation. The surface morphology of the zinc deposits was closely related to the preferred orientation of the deposits. The glossiness of Zn deposit with Fe-Ni additives was higher than that of pure Zn deposit, while the glossiness of Zn deposits with both Fe-Co and Fe-Cr additives was lower than that of pure Zn deposit. The hardness of Zn deposits with both Fe-Ni and Fe-Co additives was noticeably higher than that of Zn-Fe deposit, while that of Zn deposit with Fe-Cr additives was similar to that of Zn-Fe deposit.

• Journal of the Korean institute of surface engineering
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• v.31 no.6
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• pp.393-399
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• 1998

The composition and the properred orientation of Co-Fe-Cr alloy electrodeposits were invesigated according to the electrolysis conditions using sulface bath. The current efficiency and the cathode overpotential decrased noticeably with the increase of Cr content in the bath. As the D.C. current density increased increased, the Cr content in the alloy increasd, while Co content decreased and Fe content remained constant, In the pulse current electrolysis, the Cr content of the alloy increased with the mean current density and off-time and then its content increased mord more noticeably with the peak current density than that of D.C. electrolysis. The preferred orientation of the alloy changed from (220)+(111) to (220) with decreasing cathode overpotential.

• Journal of the Korean institute of surface engineering
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• v.27 no.1
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• pp.3-11
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• 1994

Cyclic hot corrosion studies have been carried out on(82~94) wt. % Fe-(5, 10, 15) wt. % Cr alloys con-taining either (1, 3)wt. % of Si or Pt as minor alloying elements in molten salts of($Na_2SO_4$+NaCl) between 820 and $920^{\circ}C$. Si or Pt decreased corrosion rate with the most pronounced effect being observed for alloys having 15wt. %Cr. Especially, as Si or Pt contents are increased from 1 to 3 wt. %, improved corrosion resistance was obtained. The beneficial effect of Si addition is due to the presence of the Si-rich second phase along the grain boundaries as well as the formation of the protective $SiO_2$layer between substrates and oxide scale. The Pt addition also increased the corrosion resistance by enhancing the formation ($Cr_2O_3$+layers and by increasing the adherence of the oxide scale.

• Journal of Ocean Engineering and Technology
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• v.22 no.5
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• pp.106-111
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• 2008

In this paper, study about property evaluation for the metal matrix composites fabricated by low pressure infiltration process. Aluminum alloy composite which is reinforced by Metal fiber preform was fabricated by low pressure casting process. Infiltration condition was changed the pressure infiltration time of 1 sec, 2 sec and 5 sec under a constant pressure of 0.4 MPa. The molten alloy completely infiltrated the FeCrSi metal perform regardless of the increase in the pressure acceleration time. The the porosity in the FeCrSi/AC8A composite was investigated. The porosity was reduced as the pressure acceleration time as shorter. The FeCrSi/AC8A composite was investigated the wear test for to know the relationship between Porosity and wear resistance. FeCrSi/AC8A composite at pressure acceleration time of 1sec is shown excellent wear resistance.

• Korean Journal of Materials Research
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• v.28 no.10
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• pp.595-600
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• 2018

This study investigates the microstructural properties of CoCrFeMnNi high entropy alloy (HEA) oxynitride thin film. The HEA oxynitride thin film is grown by the magnetron sputtering method using nitrogen and oxygen gases. The grown CoCrFeMnNi HEA film shows a microstructure with nanocrystalline regions of 5~20 nm in the amorphous region, which is confirmed by high-resolution transmission electron microscopy (HR-TEM). From the TEM electron diffraction pattern analysis crystal structure is determined to be a face centered cubic (FCC) structure with a lattice constant of 0.491 nm, which is larger than that of CoCrFeMnNi HEA. The HEA oxynitride film shows a single phase in which constituting elements are distributed homogeneously as confirmed by element mapping using a Cs-corrected scanning TEM (STEM). Mechanical properties of the CoCrFeMnNi HEA oxynitride thin film are addressed by a nano indentation method, and a hardness of 8.13 GPa and a Young's modulus of 157.3 GPa are obtained. The observed high hardness value is thought to be the result of hardening due to the nanocrystalline microstructure.