• Tribology and Lubricants
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• v.28 no.2
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• pp.56-61
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• 2012

In order to investigate the possibility of Ni-Al based intermetallics coating onto aluminum substrate, the coating process for induction heating has been evaluated by microscopically analyzing the intermetallic layers coated at temperatures lower than the melting temperature of aluminum. The coating layers were divided into two parts with different microstructure along the depth. Hard $NiAl_3$ layer was found at lower parts of the coatings near the interface with aluminum substrate. This layer was formed by the diffusion of aluminum atoms from the substrate into the coating layer across the interface during the induction heating. Meanwhile, at the upper parts of the coating near the surface, a large amount of un-reacted Ni was still remained and surrounded by several Ni-Al based intermetallic compounds, such as $Ni_3Al$, NiAl and $Ni_2Al_3$ formed by the lattice diffusion.

• Tribology and Lubricants
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• v.27 no.1
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• pp.1-6
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• 2011

The possibility of Cu-Al-Ni intermetallic coating on the mild steel through the combustion synthesis has been investigated. In particular, the effect of the ball milling energy on the microstructure of the coating layer was examined to obtain the best coating condition. Experimental results show that Cu-Al-Ni powder compact was explosively synthesized and successfully coated with the steel matrix. It was revealed that the formation of $Cu_9Al_4$ intermetallic decreased with increase in the ball milling energy. This result supports that the high energy ball milling would be effective for obtaining the most suitable microstructure for Cu-Al-Ni coating layer. However, the excessive ball milling energy seems to decrease the bonding strength between the coating layer and the matrix.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.131-131
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• 2018

최근 절삭공구산업은 자동차, 항공기, IT, 선박, 에너지 등 첨단산업의 증가로 인해 CGI, CFRP, 내열합금 등 난삭재의 수요가 증가하고 있다. 난삭재는 고내열, 고경도, 초경량 같은 특성을 지니며 우수한 기계적 물성을 갖지만 가공의 어려움이 있어 산업에 적용하는데 한계가 있다. 이러한 한계를 극복하기 위해 개발된 가공기술 중 하드 코팅은 공구코팅비용 대비 공구의 표면경도와 수명을 효율적으로 향상시킬 수 있다고 알려져 있다. 대표적인 하드코팅으로는 AlN계, TiN계 코팅이 있다. 이러한 코팅의 경우 높은 기계적 물성과 우수한 내마모성으로 인해 절삭공구의 성능을 향상시킬 수 있기 때문에, 많은 연구가 진행되고 있으며 절삭공구산업에서 각광받고 있다. 기존 선행연구 결과에 따르면 질화물 코팅의 우수한 물성은 질화물(Nitride) 생성 및 질화 공정에 의한 코팅층의 고밀도화에 의해 나타난다고 알려져 있다. 그 중에서 AlCrN coating은 우수한 내마모성 및 향상된 고온경도를 갖고 있다. AlCrN based coating에 미량의 원소를 첨가하여 기존 AlCrN coating의 기계적 특성을 더욱 향상 시킨 coating은 일반적인 고성능 코팅 대비 공구수명이 길다고 알려져 있으며, 전반적으로 우수한 특성에 의해 전 세계적으로 습식 및 건식 기계 가공 용도로 사용되고 있다. 본 연구에서는 AlCrN based coating에 미량의 원소를 첨가한 coating의 우수한 기계적 특성의 원인을 규명하기 위해 텅스텐카바이드(WC) 기판 위에 아크 이온 플레이팅 장비를 이용하여 AlCrN based coating을 증착 시킨 sample을 분석하였다. 결정구조 및 상 분석을 위해 X선 회절분석(XRD)을 실시하였으며, 미세 구조를 분석하기 위해 전계방출형 주사전자현미경(FE-SEM), 투과 전자현미경(TEM) 분석을 실시하였다. 또한 코팅층의 화학적 성분 분석을 위해 EDX분석을 실시하였으며 기계적 특성 평가를 위해 나노압입시험(Nano-indentation test)을 진행하였다.

• Bulletin of the Korean Chemical Society
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• v.17 no.7
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• pp.621-625
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• 1996

A variety of metal oxides were coated by sol-gel process from their metal alkoxides on the ribbons of Co-based and Fe-based amorphous alloys, and the effects of surface oxide coating on the magnetic properties of the alloy are investigated. The core loss is found to be reduced significantly by the oxide coating, the loss reduction becoming more prominent at higher frequencies. The shape of the hystersis loop is also dependent upon the kind of the coated metal oxide. The coatings of MgO, SiO2, MgO·SiO2 and MgO·Al2O3 induce tensile stress into the Fe-based ribbon whereas those of BaO, Al2O3, CaO·Al2O3, SrO·Al2O3 and BaO·Al2O3 induce compressive stress. These results may be explained by the modification of domain structures via magnetoelastic interactions with the shrinkage stress induced by the sol-gel coating.

• Journal of the Korean Society for Heat Treatment
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• v.19 no.2
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• pp.103-108
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• 2006

Microstructural evolution of Pt-aluminide coated Ni-based superalloy has been investigated with ductilization heat treatment. The Pt coat was prepared on the superalloy and then aluminide coating was conducted using a pack cementation process. Samples were heat-treated at $1050^{\circ}C$ for 2 hrs and the microstructure and element analysis were preformed. A various precipitated compounds were observed within the coating layer and the diffusion region in the Pt-aluminide coating and heat treatment, indicating that the bi-phase compounds of $PtAl_2$ and NiAl were performed during the Pt-aluminide coating, whereas $M_{23}C_6$, MC, $Ni_3Al$ and ${\sigma}$ phases were precipitated in the inter-diffusion region. The bi-phase compounds of $PtAl_2$ and NiAl were transformed into the single phase compound of $PtAl_2$ with the heat treatment, increasing the amount of carbide and ${\sigma}$ phase.

• Tribology and Lubricants
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• v.34 no.2
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• pp.67-73
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• 2018

Ni-Al intermetallic coating technology is an available method for the strengthening of aluminum substrate. In this study, Ni-Al intermetallics were coated on an aluminum substrate through a reaction synthesis process at a temperature lower than melting point of aluminum. And the sliding wear properties of the coatings have been investigated to verify their usability and compared the wear properties with those of a cast Al-12.5%Si alloy and an anodizing layer on aluminum. Results show that the wear rate of the coating layer greatly increased at 1 m/s and 1.5 m/s when compared with that of the cast Al-12.5%Si alloy. Much pitting damages were observed on the worn surfaces at these sliding speeds, unlike at other sliding speeds. The wear of the intermetallic coating layer at these sliding speeds seems to be increased by pitting as a consequence of adhesion. In contrast, wear of the coating layer at other speeds hardly occurs, regardless of wear periods. Nevertheless, the wear properties of the intermetallic coating layer on the aluminum substrate through the reaction synthesis process are more stable than those of anodized aluminum and are superior to those of the cast Al-12.5%Si alloy in a steady-state wear period.

• Journal of Powder Materials
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• v.27 no.3
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• pp.210-218
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• 2020

A T-800 (Co-Mo-Cr) coating material is fabricated using Co-Mo-Cr powder feedstock and laser cladding. The microstructure and melted Al erosion properties of the laser-cladded T-800 coating material are investigated. The Al erosion properties of the HVOF-sprayed MoB-CoCr and bulk T-800 material are also examined and compared with the laser-cladded T-800 coating material. Co and lave phases (Co₂MoCr and Co₃Mo₂Si) are detected in both the laser-cladded T-800 coating and the bulk T-800 materials. However, the sizes of the lave phases are measured as 7.9 ㎛ and 60.6 ㎛ for the laser-cladded and bulk T-800 materials, respectively. After the Al erosion tests, the erosion layer thicknesses of the three materials are measured as 91.50 ㎛ (HVOF MoB-CoCr coating), 204.83 ㎛ (laser cladded T-800), and 226.33 ㎛ (bulk T-800). In the HVOF MoB-CoCr coating material, coarse cracks and delamination of the coating layer are observed. On the other hand, no cracks or local delamination of the coating layer are detected in the laser T-800 material even after the Al erosion test. Based on the above results, the authors discuss the appropriate material and process that could replace conventional bulk T-800 materials used as molten Al pots.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.5
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• pp.974-980
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• 2015

Arc thermal spray coating using Al-3%Mg thermal spray wire was carried out to prevent steel from corrosion damage under the marine environment. Post-sealing was applied to Al-3%Mg spray coating treatment using organic/inorganic composite ceramics in order to improve the corrosion resistance of the as-sprayed coating. The results of various electrochemical experiments with sealing treatment indicated that the improvement in corrosion resistance was observed due to low current density in all applied potential range during anodic and cathodic polarization experiments. Futhermore, the natural potential measurement exhibited severe potential fluctuation due to influence of micro-crack presence on the surface of sealed thermal spray coating layer. In addition, the sealed layer was easily eliminated during anodic polarization. Nevertheless, Al-3%Mg spray coating layer improved corrosion resistance by sealing treatment because the sealed coating efficiency was determined to be 92.11%, indicating the exterior environment barrier effect which is based on the Tafel analysis.

• The Korean Journal of Ceramics
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• v.4 no.4
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• pp.340-344
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• 1998

Failure mechanisms were investigated for the two layer thermal barrier coatings consisting of NiCrAlY bond coat and $ZrO_2$-8wt.% $Y_2O_3$ ceramic coating during cyclic oxidation. $Al_2O_3$ developed at the ceramic coating/bond coat interface first, followed by the Cr/Ni rich oxides such as $NiCr_2O_4$ and $Ni(Al, Cr)_2O_4$ during cyclic oxidation. It was observed that the spalling of ceramic coatings took place primarily within the NiCrAlY bond coat oxidation products or at the interface between the bond coat oxidation products and zirconia based ceramic coating or the bond coat. It was also observed that the fracture within these oxidation products occurred with the formation of $Ni(Cr, Al)_2O_4$ spinel or Cr/Ni rich oxides. It was therefore concluded that the formation of these oxides was a life-limiting event for the thermal barrier coatings.

• Korean Journal of Metals and Materials
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• v.48 no.2
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• pp.141-147
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• 2010

An Ni-Al intermetallic coating has been produced by induction heating on mild steel. The effect of the induction heating conditions on the microstructure of the coating has been investigated. The reaction synthesis of the intermetallic compounds was promoted while increasing the heating rate and the holding time at reaction temperature. Especially, an NiAl phase corresponding to the initial composition of mixed powder was predominantly formed. However, the synthesis at low reaction temperatures occurred by solid state diffusion during the holding time and an Fe-Al reaction layer was formed at the interface with the substrate, regardless of the heating rate. The combustion synthesis of the intermetallic compound occurred at a temperature higher than 1023 K and resulted in an almost single phase NiAl structure.