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dc.contributor.advisorLiu, Stephen
dc.contributor.authorHawk, Cheryl
dc.date.accessioned2016-06-29T13:36:04Z
dc.date.accessioned2022-02-03T12:58:41Z
dc.date.available2016-06-29T13:36:04Z
dc.date.available2022-02-03T12:58:41Z
dc.date.issued2016
dc.identifierT 8083
dc.identifier.urihttps://hdl.handle.net/11124/170310
dc.descriptionIncludes bibliographical references.
dc.description2016 Summer.
dc.description.abstractThe effect of microstructure and processing parameters on the bend properties of wide gap braze repairs has been investigated for BNi-2 and BNi-5 filler metals. BNi-2 braze alloys developed a brittle eutectic constituent that was the source for crack initiation and propagation. BNi-5 braze alloys developed large pores and lack of fusion to the base metal René 108 that decreased the strength of the joint. Three types of crack behaviors were observed within the two braze alloys. (1) Crack initiation and propagation through the brittle eutectic constituent. (2) Crack initiation and propagation through the brittle eutectic constituent/ matrix interface. The crack would propagate through grain boundaries if the eutectic constituent was dispersed. (3) Crack propagation follows type 1 or type 2, but propagated due to a major defect and coalesced with the defect. Braze alloy chemistry was improved by changing the filler metal-additive powder ratio. For the BNi-2 braze alloys, a mixing ratio of 40 wt.% BNi-2 produced the lowest volume percent of the brittle eutectic constituent. These alloys produced the highest strengths. A ratio of 50 wt.% BNi-2 produced the highest volume percent of the brittle eutectic constituent and the lowest strengths. For the BNi-5 braze alloys, 40 wt.% BNi-5 produced the highest volume percent of voids and therefore exhibited the lowest strengths. Sixty weight percent BNi-5 exhibited the lowest volume percent of voids and therefore exhibited the highest strengths. Processing parameters were improved for the various stages in the brazing cycle by changing the time and temperature. The “brazing hold” was held at 1200°C or 1232°C for 10 minutes. The bend strength and angular deflection increased when brazed at 1232°C for 10 minutes. A brazing temperature of 1232°C improved the microstructure by reducing the amount of detrimental microstructural features. The “diffusion hold” parameters were held at 1100°C and 1121°C for 2 hours and 4 hours. The bend strength and angular defection increased with a “diffusion hold” temperature of 1121°C for both 2 hours and 4 hours. However, at 1100°C, there was an increase in strength and angular deflection with a “diffusion hold” of 2 hours but a decrease in strength when held for 4 hours.
dc.format.mediumborn digital
dc.format.mediummasters theses
dc.languageEnglish
dc.language.isoeng
dc.publisherColorado School of Mines. Arthur Lakes Library
dc.relation.ispartof2016 - Mines Theses & Dissertations
dc.rightsCopyright of the original work is retained by the author.
dc.subjectactivated diffusion healing
dc.subjectBNi-2 and BNi-5
dc.subjectcracking mechanism
dc.subjectsuperalloys
dc.subjectturbines
dc.subjectwide gap brazing
dc.titleWide gap braze repairs of nickel superalloy gas turbine components
dc.typeText
dc.contributor.committeememberYu, Zhenzhen
dc.contributor.committeememberBourne, Gerald
thesis.degree.nameMaster of Science (M.S.)
thesis.degree.levelMasters
thesis.degree.disciplineMetallurgical and Materials Engineering
thesis.degree.grantorColorado School of Mines


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