• 한국분말재료학회지
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• 제27권3호
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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.

• 대한기계학회논문집A
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• 제41권4호
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• pp.299-305
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• 2017

최근 심각한 환경오염과 경제 불황으로 인해 리엔지니어링에 대한 관심이 증가하고 있다. 조선분야에 대한 리엔지니어링은 꾸준히 진행되어 왔으나 국내에서의 선박 수리 및 유지보수 산업의 기술력과 인지도는 조선해양산업에 비해 떨어진다. 이러한 문제를 해결하기 위해 기술개발의 일환으로 레이저 클래딩을 주목할 수 있다. 레이저 클래딩은 희석률이 낮고, 기공이 거의 존재하지 않는 우수한 클래드 층을 형성하므로 본 연구는 선박용 배기밸브 페이스에 레이저 클래딩 적용을 위한 기초연구로써 다양한 공정변수에 따른 1패스 클래드 층의 특성을 조사하였다. 그 결과, 출력이 증가할수록 클래드 층의 폭은 넓어지고 높이는 감소하였다. 또한 클래드 층의 경도를 측정했을 때 경도 값이 점차 감소하였으며 EDS 성분 분석을 통해 클래드 층 전체가 희석되는 것을 확인할 수 있었다.

• Journal of Welding and Joining
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• 제29권2호
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• pp.88-93
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• 2011

This study produced hypereutectic Al-Si clad layer on 1050 Al alloy by a novel laser cladding method. Pure Si powder was mixed with organic binder to make fluid paste which could be screen-printed on the 1050 Al alloy plate. Pulsed Nd:YAG laser was irradiated on the Si paste layer to melt and alloy with Al substrate. Different laser power of 99 W, 179 W and 261 W, was used to see the difference of the microstructure, composition and hardness of the clad layers. When laser power of 179 W was used, the clad layer had overall Si content of 38wt% and composed of fine primary Si particles and fine eutectic phase. At laser power of 261 W, the clad layer had overall Si content of 24wt% and composed of mainly fine eutectic phase. Vickers hardness of HV176.7 and HV150.3 on the clad layer was obtained at laser power of 179 W and 261 W, respectively.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.256-261
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• 2001

Corrosion and tensile properties of zircaloy-4 cladding tube having a laser welding part in elevated temperature are studied to present the criterion of quality evaluation in nuclear reactor and to found the scientific basis of SCC, with laser welding method using by coupling up cladding tube to end cap. In the result of tensile test($400^{\circ}C$), the fracture is not happened in the welding part but base metal and the result of corrosion test($400^{\circ}C$ 1500psi steam), corrosion rate of the molten zone and PMZ is a little higher than the other zone.

• 한국표면공학회지
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• 제37권5호
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• pp.279-288
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• 2004

This paper describes a three-dimensional transient finite element model for a laser cladding process. In the model, an adaptive finite element technique is used for dilution control. Using the proposed finite element model, the effects of process parameters such as scanning speed, laser's power, and preheating on the dilution of clad layer, the shape of melting pool, and the temperature distribution are calculated. It is also shown that the optimal process parameters for the required dilution can be determined from the proposed finite element model. An experiment is performed to validate the proposed model. The numerical results are compared with experimental ones.

• 한국표면공학회지
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• 제27권6호
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• pp.359-367
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• 1994

• 한국레이저가공학회:학술대회논문집
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• 한국레이저가공학회 1999년도 춘계학술발표대회 논문개요집
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• pp.47-50
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• 1999

• 한국레이저가공학회:학술대회논문집
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• 한국레이저가공학회 1998년도 추계학술발표대회 초록개요집
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• pp.66-70
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• 1998

• Journal of Welding and Joining
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• 제32권6호
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• pp.41-46
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• 2014

In this study, cracking susceptibility of laser cladding was investigated according to the processing parameters such as laser power, scan speed and feeding rate with blended powders of stellite#6 and technolase40s (WC+NiCr). The solidification microstructure of clad was composed of Co-based dendrite structures with ${\gamma}+Cr7C3$ eutectic phases at the dendritic boundaries. The crack propagation showed transgranular fracture along dendritic boundaries due to brittle chrome carbide at the eutectic phases. From results of fractography experiments, the fracture surface was typical cleavage brittle fracture in the clad and substrate. The number of clad cracks, caused by a tensile stress after the solidification, increased with increase of laser power, scan speed and feeding rate. Increase of the laser power caused large pores by facilitating WC decarburizing reaction. And the pores affected increase of crack susceptibility. High scan speed caused increment of clad cracks due to thermal stress and WC particle fractures. Also, increase of the feeding rate accompanied an amount of WC particles causing crack initiation and decarburizing reaction.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.327-330
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• 2004

Laser aided direct metal deposition (LADMD) process offers the ability to make a metal component directly from 3-D CAD dimensions. A 3-D object can be formed by repeating laser cladding layer by layer. The key of the build-up mechanism is the effective control of powder delivery and laser power to be irradiated into the melt-pool. A feedback control system using optical sensors is introduced to control laser power and powder mass flow rate. Using H13 tool steel and $CO_2$ laser system, comprehensive analysis are executed to test the efficiency of the system. In addition, the dimensional characteristics of directed deposited material are investigated with the parameters of deposition thickness, laser power, traverse speed and powder mass flow rate.