Ispitivanje otpornosti višefaznih konstrukcijskih čelika na lokalnu koroziju

master's thesis

• Title (english): Resistance testing of multiphase structural steels to local corrosion
• Author: Martin Domitrović
• Mentor: Anita Begić Hadžipašić (mentor)
• Committee member: Ljerka Slokar (predsjednik povjerenstva)
• Committee member: Anita Begić Hadžipašić (član povjerenstva)
• Committee member: Stjepan Kožuh (član povjerenstva)
• Granter: University of Zagreb; Faculty of Metallurgy; Sisak
• Defense date and country: 2018-09-21, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Metallurgy

Abstract

U ovom radu ispitana je otpornost modernih višefaznih konstrukcijskih čelika na lokalnu
koroziju u 3,5%-tnoj otopini NaCl. Ispitivanja su provedena na 3 uzorka TRIP -čelika oznake
VA, J i K koji se međusobno razlikuju prema kemijskom sastavu i mehaničkim svojstvima.
Metodom cikličke anodne polarizacije dobiveni su parametri lokalne korozije te je otpornost
ispitanih čelika određena prema kriteriju piting potencijala.
Elektrokemijska mjerenja su pokazala da ispitani TRIP čelici pokazuju slabiju otpornost na
lokalnu koroziju od konvencionalnog konstrukcijskog čelika, o čemu svjedoče niži iznosi piting
potencijala. Pošto su registrirani piting potencijali ispitanih TRIP-čelika približno istih
vrijednosti, ne može se ustanoviti njihov poredak otpornosti prema lokalnoj koroziji.
Metalografska ispitivanja su pokazala da se radi o modernim TRIP-čelicima koji se sastoje iz
tri mikrostrukturne faze: ferit, bainit i zaostali austenit. Zbog izrazito sitnozrnate mikrostrukture
otpornost TRIP-čelika prema piting koroziji je uvelike smanjena, zbog mnoštva granica zrna
koje predstavljaju idealna korozijska mjesta za nastanak i razvoj pitinga.

Abstract (english)

In this paper, the resistance to local corrosion of modern multiphase structural steels in 3.5%
NaCl solution was investigated. The tests were performed on the three samples of TRIP steels
marked as VA, J and K which differ by the chemical composition and mechanical properties.
By the method of cyclic anode polarization, the local corrosion parameters were obtained and
the resistance of the tested steels was determined according to the pit ting potential criterion.
Electrochemical measurements have shown that tested TRIP steels exhibit less resistance to
local corrosion than conventional structural steel, as evidenced by lower pit ting potential. Since
the registered pitting potentials of the tested TRIP-steels are approximately the same, their order
of resistance to local corrosion can not be established.
Metalographic analysis has shown that this modern TRIP steels consist of three microstructural
phases: ferrite, bainite and residual austenite.
Because of the extremely fine-grained microstructure, the resistance to pitting corrosion is
greatly reduced due to the multitude of grain boundaries that represent the ideal corrosion sites
for the occurrence and development of the pittings.

• Keywords: korozijska otpornost; TRIP-čelik; lokalna korozija; piting potencijal; mikrostruktura
• Keywords (english): corrosion resistance; TRIP-steels; local corrosion; pitting potential; microstructure
• Language: croatian
• URN:NBN: urn:nbn:hr:115:498894
• Study programme: Title: Graduate study program Metallurgy; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka metalurgije (magistar/magistra inženjer/inženjerka metalurgije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2018-09-28 07:42:35