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전기도금법에 의해 생성된 Ni-B 합금도금층의 물성에 미치는 B 함량의 영향
이규환(Kyu Hwan Lee),장도연(Doyon Chang),권식철(Sik Chul Kwon) 한국표면공학회 2004 한국표면공학회지 Vol.37 No.4
The influence of the boron content on the various properties of Ni-B alloy films produced by electrodeposition was investigated. The considerable reduction in grain size was observed with increasing boron content. The internal stress was tensile and increased linearly with increasing boron content. Hardness increased up to 750Hv at 2 at% boron and then kept the value to 11 at% boron for as-plated Ni-B coatings. The hardness of Ni-B films increased up to 1,250Hv due to the intermetallic Ni₃B precipitation by the heat treatment, and maximum hardness of each coating increases with boron content. Wear resistance decreased with increasing the boron content because of high friction coefficient and brittle fracture of film which has higher content of boron.
Zinc Phosphate Conversion Coatings on Magnesium Alloys: A Review
Nguyen Van Phuong,Kyuhwan Lee,Doyon Chang,Man Kim,Sangyeoul Lee,Sungmo Moon 대한금속·재료학회 2013 METALS AND MATERIALS International Vol.19 No.2
Phosphating is one of the most widely used surface treatments of steels and aluminum due to its low-cost,easy mass production, good corrosion resistance and good adhesion with paint. Many researchers have tried to expand applications of the phosphating process, especially to magnesium alloys for automobiles and aerospace applications. Recently, the coatings on magnesium alloys by zinc phosphate conversion coatings (Zn3(PO4)2.4H2O) have been intensively studied. This paper reviews the state-of-the-art of phosphate conversion coatings developed for magnesium alloys, in terms of coating properties, phosphate conversion coatings processes and compositions of phosphating bath.
High Temperature Oxidation and Sulfidation of Ni-15at.%W Coatings
Chanwou Kim,Teayoul You,Yuriy Shapovalov,Jaehwang Ko,Dongbok Lee,Kyuhwan Lee,Doyon Chang,Dongsoo Kim,Sikchol Kwon 한국표면공학회 2005 한국표면공학회지 Vol.38 No.1
Ni-15at. %W coatings with film thicknesses of 20-40 ㎛ were electroplated on a steel substrate, and their oxidation behavior was investigated at 700 and 800℃ in air. For comparison, a pure Ni coating and a bulk Ni were also oxidized. The Ni-15at. %W coating displayed the worst oxidation resistance, due to the formation of less-protective NiO, Fe₂O₃, NiFe₂O₄and NiWO₄. The corrosion behavior Ni-15at.%W coatings electroplated on a steel substrate was similarly investigated at 700 and 800℃ in the Ar-1%SO₂ atmosphere. For comparison, the uncoated steel substrate was also corrosion-tested in the Ar-1%SO₂ atmosphere. Severe scale spallation and the internal corrosion of the steel that occurred in the uncoated substrate were not observed in the coated specimen. However, it seemed that the Ni-15at.%W coating cannot be a potential candidate as a sulfidation-resistant coating, due to the formation of less-protective NiO, NiS, WO₃ and NiWO₄.