Title Prilog razvoju bestrujnoga postupka otvrdnjavanja površine nehrađajućeg čelika : doktorska disertacija Title (english) Contribution to the developmenmt of electroless process of hardening stainless steel surface : doctoral thesis Author Mauro Maretić Mentor Božo Smoljan (mentor)Mentor Dario Iljkić (komentor)Committee member Sunčana Smokvina Hanza (predsjednik povjerenstva)Committee member Božo Smoljan (član povjerenstva)Committee member Vojteh Leskovšek (član povjerenstva) Granter University of Rijeka Defense date and country 2017-06-20, Croatia Scientific / art field, TECHNICAL SCIENCES Universal decimal classificationUDC ) 669 - Metallurgy Abstract Povećanje tvrdoće površine austenitnog čelika postupkom bestrujnoga nanošenja Ni-P
prevlake, uz postizanje adekvatne adhezivnosti prevlake, zahtjevan je zadatak inženjerstva
površina. Cilj ovog istraživanja bio je proširenje dosadašnjih spoznaja u području bestrujnoga
niklanja te proširenje spoznaja o samoj Ni-P prevlaci, sa svrhom poboljšanja svojstava nanesene
prevlake i razvoja postupka bestrujnoga nanošenja Ni-P prevlake na austenitni čelik.
Osnovna razlika postupka bestrujnoga niklanja i ostalih galvanskih postupaka je u tome što se
postupak bestrujnoga niklanja izvodi bez korištenja izvora električne struje, uranjanjem
supstrata u elektrolit, pri čemu dolazi do disocijacije površinskih atoma supstrata, uz
istovremenu disocijaciju elektrolita. Prevlaka se stvara vezivanjem kationa nikla iz elektrolita
sa negativno nabijenom površinom supstrata.
Provedena opsežna teorijska i eksperimentalna istraživanja dovela su do novih saznanja koja
su omogućila optimizaciju tehnološkog procesa postupka bestrujnoga nanošenja Ni-P prevlake
na osnovni materijal – austenitni čelik oznake X5CrNiMo17-12-2 (HRN EN). U ovom radu po
prvi puta predložena je aktivacija površine austenitnog čelika dodavanjem aluminijske
elektrode u procesu bestrujnoga niklanja austenitnog nehrđajućeg čelika. Na taj način
izostavljena je aktivacija površine austenitnog čelika „nickel strike“ postupkom stvaranja
tankog sloja nikla na površini, što u dosadašnjoj praksi nije bilo moguće.
Također, utvrđeni su optimalni parametri postupka toplinske obrade, kojima se poboljšava
adhezivnost nanesene Ni-P prevlake, dok su analizom mikrostrukture ustanovljene promjene u
mikrostrukturi koje poboljšavaju adhezivnost nanesene prevlake.
Uz adekvatna svojstva prevlake, za potrebe industrijske proizvodnje bitna je i cijena
tehnološkog postupka nanošenja prevlake. Razvijeni tehnološki proces nanošenja Ni-P
prevlake na austenitni čelik aktivacijom površine čelika aluminijskom elektrodom proširio je
spektar tehnoloških procesa nanošenja Ni-P prevlake i dao veću mogućnost odabira
ekonomičnijeg postupka u procesu proizvodnje, ovisno o vrsti proizvodnje i obliku izradaka,
što za posljedicu ima veću konkurentnost proizvođača na tržištu.
Ovim istraživanjima otvoreni su novi horizonti u razvoju postupaka bestrujnoga nanošenja NiP prevlaka na austenitni čelik te doneseni zaključci koji mogu utjecati na poboljšanje postupka
bestrujnoga nanošenja Ni-P prevlake, kao i na ekonomičniju proizvodnju.
Abstract (english) Hardening of austenitic stainless steel surface by electroless deposition of Ni-P coating and
achieving its adequate adhesion is a demanding task of surface engineering. Widening of the
existing knowledge of electroless nickel plating and knowledge regarding Ni-P layer itself, with
purpose of improvement of properties of the deposited layer and development of the electroless
Ni-P plating process, was the main goal of this research. In comparison to other galvanic
processes, electroless nickel plating is performed with no electricity source used, by immersion
of material in the electrolyte which causes dissociation of material’s surface atoms and
electrolyte dissociation at the same time. Coating is created by nickel cations from electrolyte,
which are binding to the negatively charged material surface.
By theoretical and experimental research, new findings, which enabled optimization of
technological process of electroless Ni-P plating of the base material – X5CrNiMo17-12-2
(HRN EN) austenitic stainless steel, have been found. In this thesis, activation of the surface of
the austenitic steel by adding an aluminum electrode in the electroless nickel plating has been
proposed for the first time. In this way, activation of the surface by nickel strike method of
producing a thin nickel layer on the surface has been left out, which was not possible in practice
so far.
Optimal parameters of heat treatment which increase adhesion of deposited Ni-P coating have
been determined and by analysis of microstructure, microstructural changes which increase
adhesion of the deposited layer have been determined as well.
For the industrial purpose, except adequate mechanical properties of the coating, cost of
technological process of deposition is important as well. Developed technological process of
deposition of Ni-P coating on the austenitic steel by activation of the steel surface using
aluminum electrode has expanded the range of available technological processes of deposition
of Ni-P coating, and has given the greater possibility of choosing more economical production
procedure, depending on the production type and specimen shape. Consequently, it gives
greater competitiveness to manufacturers.
By this research, new horizons in the development of electroless deposition of Ni-P coating on
the austenitic steel have been opened. Conclusions of this research improve process and cost
effectiveness of production of these coatings.
Keywords
bestrujno niklanje
Ni-P prevlaka
tvrdoća
adhezija
austenitni čelik
kemijska analiza
supstrat
Keywords (english)
electroless nickel
Ni-P coating
hardness
adhesion
austenitic steel
chemical analysis
substrate
Language croatian URN:NBN urn:nbn:hr:190:975147 Promotion 2020 Study programme Title: Postgraduate university (doctoral) study Type of resource Text Extent VI, 153 str. ; 30 cm File origin Born digital Access conditions Open access Terms of use Created on 2020-10-22 10:28:27
