{"id":{"repo_id":"unsw","oai_identifier":"oai:unsworks.library.unsw.edu.au:1959.4/51932"},"canonical_url":"https://search.dev.ndltd.org/etd/unsw/oai:unsworks.library.unsw.edu.au:1959.4/51932","repository":{"repo_id":"unsw","name":"University of New South Wales","base_url":"https://unsworks.unsw.edu.au/oai/provider"},"display":{"title":"Controlled Surface Layer Deposition for Steel Surface Hardening","abstract":"Electrophoretic deposition (EPD) of Ti on low carbon steel followed by heat treatment, which was done at 600-1400 degree celsius for 1 h or 9 h under Ar (sintering) and 5% H2-N2 (nitridation), were used for surface hardening. The coarse Ti particles (≤50 μm) were suspended in ethanol using the charging agent poly(diallyldimethylammonium chloride) (PDADMAC). EPD: The present work demonstrated the importance of assessing the electrophoretic mobilities of both the suspensions and solutions since the latter plays a critical role in interpretation. Algebraic uncoupling of these data plus determination of the deposit yield as a function of charging agent addition allowed discrimination between the three mechanistic stages of the electrokinetics of the process: (1) surface saturation; (2) compression of the diffuse layer, growth of a polymer-rich layer, and/or competition between the mobility of Ti and PDADMAC; and (3) little or no decrease in electrophoretic mobility of Ti, establishment of a polymer-rich layer, and/or dominance of the mobility of the PDADMAC over that of Ti. Heat treatment: Although oxygen contamination of the furnace atmosphere was a concern, development of the relevant Fe-Ti-O isothermal sections allowed: (a) unambiguous interpretation of the results, and (b) consideration of the importance of liquid formation. The Ti-based coatings and steel substrates were mutually exclusive in terms of their phase distributions and microstructures at all temperatures. A tentative Onion Skin model was used to explain the cross-sectional phase distribution in the coating of the samples. A thermal expansion mismatch model was used to describe coating delamination and vertical crack formation, propagation, and branching. The optimal coating was obtained at 1400 degree celsius for 9 h in Ar. The coating consisted of ulvöspinel (Fe2TiO4), wüstite (FeO), and ferrite (αFe). The coating microstructure and its phase assemblage were dominated by the liquid formation reactions: (a) FeO (liq) + TiO (sol) → αFe (sol) + TiO2 (sol), (b) 2FeO (liq) + TiO2 (sol) → Fe2TiO4 (sol), and (c) FeO (liq) → FeO (sol). The reaction path was explained by the Fe-Ti-O isothermal section. Improved contact between the coating and steel resulted from wetting of the steel substrate by the liquid FeO.","abstract_html":"Electrophoretic deposition (EPD) of Ti on low carbon steel followed by heat treatment, which was done at 600-1400 degree celsius for 1 h or 9 h under Ar (sintering) and 5% H2-N2 (nitridation), were used for surface hardening. The coarse Ti particles (≤50 μm) were suspended in ethanol using the charging agent poly(diallyldimethylammonium chloride) (PDADMAC). EPD: The present work demonstrated the importance of assessing the electrophoretic mobilities of both the suspensions and solutions since the latter plays a critical role in interpretation. Algebraic uncoupling of these data plus determination of the deposit yield as a function of charging agent addition allowed discrimination between the three mechanistic stages of the electrokinetics of the process: (1) surface saturation; (2) compression of the diffuse layer, growth of a polymer-rich layer, and/or competition between the mobility of Ti and PDADMAC; and (3) little or no decrease in electrophoretic mobility of Ti, establishment of a polymer-rich layer, and/or dominance of the mobility of the PDADMAC over that of Ti. Heat treatment: Although oxygen contamination of the furnace atmosphere was a concern, development of the relevant Fe-Ti-O isothermal sections allowed: (a) unambiguous interpretation of the results, and (b) consideration of the importance of liquid formation. The Ti-based coatings and steel substrates were mutually exclusive in terms of their phase distributions and microstructures at all temperatures. A tentative Onion Skin model was used to explain the cross-sectional phase distribution in the coating of the samples. A thermal expansion mismatch model was used to describe coating delamination and vertical crack formation, propagation, and branching. The optimal coating was obtained at 1400 degree celsius for 9 h in Ar. The coating consisted of ulvöspinel (Fe2TiO4), wüstite (FeO), and ferrite (αFe). The coating microstructure and its phase assemblage were dominated by the liquid formation reactions: (a) FeO (liq) + TiO (sol) → αFe (sol) + TiO2 (sol), (b) 2FeO (liq) + TiO2 (sol) → Fe2TiO4 (sol), and (c) FeO (liq) → FeO (sol). The reaction path was explained by the Fe-Ti-O isothermal section. Improved contact between the coating and steel resulted from wetting of the steel substrate by the liquid FeO.","abstract_has_math":false,"creators":["Lau, KT"],"institution":"UNSW, Sydney","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2012,"date_issued":"2012","date_published":"2012","updated_at":"2026-07-24T05:33:18Z","subjects":["Poly(diallyldimethylammonium chloride)","Titanium","Steel","Electrophoretic mobility","Diffusion","Nitridation","Oxidation"],"languages":["EN"],"rights":["open access","CC BY-NC-ND 3.0","free_to_read"],"rights_urls":["https://purl.org/coar/access_right/c_abf2","https://creativecommons.org/licenses/by-nc-nd/3.0/au/"],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["https://doi.org/10.26190/unsworks/15484"],"render_values":[{"text":"https://doi.org/10.26190/unsworks/15484","href":"https://doi.org/10.26190/unsworks/15484","code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/1959.4/51932","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Lau, KT"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2012"]},{"key":"dc:publisher","label":"Institution","values":["UNSW, Sydney"]},{"key":"dc:type","label":"Dc Type","values":["doctoral thesis","http://purl.org/coar/resource_type/c_db06"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Poly(diallyldimethylammonium chloride)","Titanium","Steel","Electrophoretic mobility","Diffusion","Nitridation","Oxidation"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["EN"]},{"key":"dc:rights","label":"Dc Rights","values":["open access","https://purl.org/coar/access_right/c_abf2","CC BY-NC-ND 3.0","https://creativecommons.org/licenses/by-nc-nd/3.0/au/","free_to_read"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/1959.4/51932","https://unsworks.unsw.edu.au/bitstreams/b86166ed-b36c-4718-adfd-7feb69571e69/download","https://doi.org/10.26190/unsworks/15484"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Electrophoretic deposition (EPD) of Ti on low carbon steel followed by heat treatment, which was done at 600-1400 degree celsius for 1 h or 9 h under Ar (sintering) and 5% H2-N2 (nitridation), were used for surface hardening. The coarse Ti particles (≤50 μm) were suspended in ethanol using the charging agent poly(diallyldimethylammonium chloride) (PDADMAC). EPD: The present work demonstrated the importance of assessing the electrophoretic mobilities of both the suspensions and solutions since the latter plays a critical role in interpretation. Algebraic uncoupling of these data plus determination of the deposit yield as a function of charging agent addition allowed discrimination between the three mechanistic stages of the electrokinetics of the process: (1) surface saturation; (2) compression of the diffuse layer, growth of a polymer-rich layer, and/or competition between the mobility of Ti and PDADMAC; and (3) little or no decrease in electrophoretic mobility of Ti, establishment of a polymer-rich layer, and/or dominance of the mobility of the PDADMAC over that of Ti. Heat treatment: Although oxygen contamination of the furnace atmosphere was a concern, development of the relevant Fe-Ti-O isothermal sections allowed: (a) unambiguous interpretation of the results, and (b) consideration of the importance of liquid formation. The Ti-based coatings and steel substrates were mutually exclusive in terms of their phase distributions and microstructures at all temperatures. A tentative Onion Skin model was used to explain the cross-sectional phase distribution in the coating of the samples. A thermal expansion mismatch model was used to describe coating delamination and vertical crack formation, propagation, and branching. The optimal coating was obtained at 1400 degree celsius for 9 h in Ar. The coating consisted of ulvöspinel (Fe2TiO4), wüstite (FeO), and ferrite (αFe). The coating microstructure and its phase assemblage were dominated by the liquid formation reactions: (a) FeO (liq) + TiO (sol) → αFe (sol) + TiO2 (sol), (b) 2FeO (liq) + TiO2 (sol) → Fe2TiO4 (sol), and (c) FeO (liq) → FeO (sol). The reaction path was explained by the Fe-Ti-O isothermal section. Improved contact between the coating and steel resulted from wetting of the steel substrate by the liquid FeO."]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Controlled Surface Layer Deposition for Steel Surface Hardening"]}]}],"canonical_facts":{"dc:creator":["Lau, KT"],"dc:date":["2012"],"dc:description":["Electrophoretic deposition (EPD) of Ti on low carbon steel followed by heat treatment, which was done at 600-1400 degree celsius for 1 h or 9 h under Ar (sintering) and 5% H2-N2 (nitridation), were used for surface hardening. The coarse Ti particles (≤50 μm) were suspended in ethanol using the charging agent poly(diallyldimethylammonium chloride) (PDADMAC). EPD: The present work demonstrated the importance of assessing the electrophoretic mobilities of both the suspensions and solutions since the latter plays a critical role in interpretation. Algebraic uncoupling of these data plus determination of the deposit yield as a function of charging agent addition allowed discrimination between the three mechanistic stages of the electrokinetics of the process: (1) surface saturation; (2) compression of the diffuse layer, growth of a polymer-rich layer, and/or competition between the mobility of Ti and PDADMAC; and (3) little or no decrease in electrophoretic mobility of Ti, establishment of a polymer-rich layer, and/or dominance of the mobility of the PDADMAC over that of Ti. Heat treatment: Although oxygen contamination of the furnace atmosphere was a concern, development of the relevant Fe-Ti-O isothermal sections allowed: (a) unambiguous interpretation of the results, and (b) consideration of the importance of liquid formation. The Ti-based coatings and steel substrates were mutually exclusive in terms of their phase distributions and microstructures at all temperatures. A tentative Onion Skin model was used to explain the cross-sectional phase distribution in the coating of the samples. A thermal expansion mismatch model was used to describe coating delamination and vertical crack formation, propagation, and branching. The optimal coating was obtained at 1400 degree celsius for 9 h in Ar. The coating consisted of ulvöspinel (Fe2TiO4), wüstite (FeO), and ferrite (αFe). The coating microstructure and its phase assemblage were dominated by the liquid formation reactions: (a) FeO (liq) + TiO (sol) → αFe (sol) + TiO2 (sol), (b) 2FeO (liq) + TiO2 (sol) → Fe2TiO4 (sol), and (c) FeO (liq) → FeO (sol). The reaction path was explained by the Fe-Ti-O isothermal section. Improved contact between the coating and steel resulted from wetting of the steel substrate by the liquid FeO."],"dc:format":["application/pdf"],"dc:identifier":["http://hdl.handle.net/1959.4/51932","https://unsworks.unsw.edu.au/bitstreams/b86166ed-b36c-4718-adfd-7feb69571e69/download","https://doi.org/10.26190/unsworks/15484"],"dc:language":["EN"],"dc:publisher":["UNSW, Sydney"],"dc:rights":["open access","https://purl.org/coar/access_right/c_abf2","CC BY-NC-ND 3.0","https://creativecommons.org/licenses/by-nc-nd/3.0/au/","free_to_read"],"dc:subject":["Poly(diallyldimethylammonium chloride)","Titanium","Steel","Electrophoretic mobility","Diffusion","Nitridation","Oxidation"],"dc:title":["Controlled Surface Layer Deposition for Steel Surface Hardening"],"dc:type":["doctoral thesis","http://purl.org/coar/resource_type/c_db06"]},"updated_at":"2026-07-24T05:33:18Z"}