Formation of Ni Aluminide Layer Containing La by Molten-Salt Electrodeposition and Cyclic-Oxidation Resistance

2006 ◽  
pp. 377-384 ◽  
Author(s):  
Michihisa Fukumoto ◽  
Motoi Hara ◽  
Toshio Narita
Keyword(s):  
Molten Salt ◽  
Oxidation Resistance ◽  
Cyclic Oxidation ◽  
Aluminide Layer

Formation of Ni Aluminide Layer Containing La by Molten-Salt Electrodeposition and Cyclic-Oxidation Resistance

2006 ◽  
Vol 522-523 ◽  
pp. 377-384 ◽  
Author(s):  
Michihisa Fukumoto ◽  
Motoi Hara ◽  
Toshio Narita
Keyword(s):  
Stainless Steel ◽  
Molten Salt ◽  
Oxidation Resistance ◽  
Cross Section ◽  
Outer Layer ◽  
Cyclic Oxidation ◽  
Polarization Method ◽  
Potentiostatic Polarization ◽  
Aluminide Layer ◽  
Deposit Layer

In order to improve the cyclic-oxidation resistance of Ni and SUS304 steel, the coating of a Ni aluminide containing La on both samples were carried out by the electrodeposition of Al and La in a molten salt. The electrodepositions of Al and La were conducted using a potentiostatic polarization method at 1023 K in an equimolar NaCl-KCl melt containing 3.5 mol%AlF3, and that containing 4 mol%La2O3-24 mol%NH4Cl, or 3.5 mol%LaF3. Observation and analysis of the cross-section of the specimen after polarization showed that a deposited layer consisting of a thick inner Ni aluminide layer and a thin outer layer containing a large amount of La was formed on both samples. The cyclic-oxidation resistance of the Ni specimen covered with the deposit layer having the La layer as the outer layer was higher than those of the untreated Ni specimen and the Ni specimen coated with the deposit layer without La. The stainless steel covered with the Ni aluminide showed a high cyclic-oxidation resistance in the atmosphere containing water vapor at 1273 K in comparison with untreated stainless steel, without depending on the existence of La in the deposited layer.

Formation of Ni Aluminide Coating Containing Reactive Elements by Simultaneous Electrodeposition and Cyclic Oxidation Resistance

2011 ◽  
Vol 696 ◽  
pp. 372-377
Author(s):  
Michihisa Fukumoto ◽  
Tsuyoshi Yokota ◽  
Motoi Hara ◽  
Toshio Narita
Keyword(s):  
Oxidation Resistance ◽  
Cyclic Oxidation ◽  
Aluminide Coating ◽  
Surface Region ◽  
Mass Gain ◽  
Salt Bath ◽  
Ni Substrate ◽  
Cyclic Oxidation Test ◽  
Aluminide Layer ◽  
Simultaneous Electrodeposition

A Ni aluminide layer containing Zr or Hf was formed on a Ni specimen by the simultaneous electrodeposition of Al and Zr or Al and Hf using a molten-salt bath. When the simultaneous electrodeposition of Al and Zr was carried out using molten NaCl-KCl containing 3.5 mol%AlF3 and 0.05 mol%ZrF4, the electrodeposited layers were formed in the order of Ni2Al3, NiAl3 and Al from the Ni substrate side. The ZrAl3 particles were uniformly formed in the surface region of the NiAl3 and Al layers. On the other hand, when the simultaneous electrodeposition of Al and Hf was carried out using molten NaCl-KCl containing 3.5 mol%AlF3 and 0.05 mol%HfF4, the electrodeposited layer consisted of Ni2Al3 as the inner layer and NiAl3 as the outer layer were formed with HfAl3 particles uniformly formed in the surface region of the NiAl3 layer. For the sample treated with the simultaneous electrodeposition of Al and Zr, no significant change in the mass gain was observed during the cyclic-oxidation test at 1423 K, suggesting that the sample had a high cyclic-oxidation resistance. Similarly, the sample treated by the simultaneous electrodeposition of Al and Hf had a high cyclic-oxidation resistance. An adhesive scale, having localized inward penetrations consisting of Al2O3 containing ZrO2 or HfO2, was formed on the samples having the high cyclic-oxidation resistance.

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