Post-Weld Oxidation Behavior of AA6061 Al Alloy

Welded AA6061 Al alloy using ER5356 (Al-5Mg) filler was oxidized in flowing air gas for 40hrs at 600oC at a total pressure of approximately 1 atm. The morphology and microstructure of welded joint after exposure was characterized by using optical metallurgy microscopy and Scanning Electron Microscope (SEM). Different oxide morphologies and textures were observed on parent and fusion metal due to the differences of the alloying element. The oxidation mechanism represented a complex reaction occur where the morphology and phase formation of the oxide shows the protective oxide scales showed the protective oxide were developed on parent metal side, meanwhile non-protective oxide scale formed on fusion metal of the welded Al alloy. It can be concluded that the welded area failed to resist oxidation behavior compared to the parent metal. The differ results are discuss in term of microstructure changes caused by high temperature oxidation exposure and alloying element.

Ni Layer Evolution of FeCrAl Substrate Treated by Ultrasonic and Electroplating Methods in Long Term Oxidation at 900°C

The long term oxidation test of FeCrAl substrate treated by ultrasonic and electroplating methods was performed at 9000C in air environment for 100 hours. The purpose of this paper is to show the nickel layer evolution of that substrate. Oxide scale and layer evolution were assessed on specimens using scanning electron microscope (SEM) coupled with energy dispersive X-ray spectroscopy (EDX). The nickel layer disappeared and fully converted to be nickel oxide on FeCrAl treated using ultrasonic and nickel electroplating after oxidation exposure at 9000 C in air for 100 hours. In this condition, the nickel oxide still existed. Not only nickel oxide and Al2O3 were occurred when oxidation exposure at this condition but also Cr2O3 and Fe2O3. The lowest parabolic rate constant was obtained from FeCrAl ultrasonic treatment with SiC for 50 minutes at 1.21 x 10-4 mg2mm4h-1, and FeCrAl ultrasonic treatment with Al2O3 for 30 minutes at 1.15 x 10-4 mg2mm4h-1. The lower parabolic rate constant indicated the higher long time to failure of the FeCrAl substrate.

Oxidation Behaviour of Ieabct Deposited NiCoCrAlY-ZrO2·y2O3 Coating

ABSTRACTThe oxidation behaviour of NiCoCrAlY-ZrO2·y2O3 coatings produced by using an ion-electron-atom beams combination technique (IEABCT) was studied after air exposure at 1100 °C for up to 300 hours. It was found that pores were dispersed in the coating, especially in the interface between coating and substrate, and no spallation or separation of the ceramic layer from the metallic bond layer were observed. The composition and morphology of the coatings before and after oxidation exposure in air at 1100 °C for 300 hours were examined by microscopy and electron microprobe analysis (EMPA).