Oxidation behavior of laser clad nickel-aluminum-chromium-hafnium alloys

Controversy regarding the mechanism(s) responsible for the retention of alumina scales formed on NiAlCr alloys containing reactive elements remains. Laser cladding is the process where a mechanical mixture of powders is rapidly melted and fused to a solid substrate using a CO$\sb2$ laser. The effects of laser cladding upon scale retention on NiAlCrHf alloys after cyclic and isothermal exposure to air were investigated. The stress developed in the scale during cooling after exposure was estimated using a thermoelastic model. Additions of up to $\approx$2${1\over2}$ wt % Hf increasingly promote retention of scales grown at 1200$\sp\circ$C. Laser clad samples containing $\approx$2${1\over2}$ wt % Hf retained almost intact scales. The improvement in scale retention is due to improved toughness in scales containing hafnia-rich polycrystallites possibly via microcracking initiated by anisotropic thermall contraction of the hafnia. Laser cladding provides a large concentration of $\approx$1μm Hf-rich particles that are precursors of the hafnia in the scale as well as a fine dendrite spacing that reduces the mean free distance between particles.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Materials Science and Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2011

Author dc:creator

• Ribaudo, Carl Robert

Contributors dc:contributor

• Mazumder, Jyotirmoy

• Engineering, Metallurgy

Statement dc:rights

• Copyright 1991 Ribaudo, Carl Robert

Language dc:language

eng

Identifier

AAI9136713
(UMI)AAI9136713

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/19888