Utjecaj mikrostrukture brzoreznog čelika na tribološka svojstva reznih alata

Šolić, Sanja (2011) Utjecaj mikrostrukture brzoreznog čelika na tribološka svojstva reznih alata. = Influence of the high speed steel microstructure on tribological properties of cutting tools. Doctoral thesis , Sveučilište u Zagrebu, Fakultet strojarstva i brodogradnje, UNSPECIFIED. Mentor: Cajner, Franjo.

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Abstract (Croatian)

U okviru ovog doktorskog rada ispitan je utjecaj mikrostrukture na tribološka svojstva brzoreznog čelika te reznih alata izrađenih od brzoreznog čelika prevučenih TiAlN prevlakom. Ispitivani brzorezni čelik dobiven je metalurgijom praha oznake Böhler PM S390 MC. Različita mikrostrukturna stanja ovog čelika dobivena su toplinskom obradom na dva načina: konvencionalno (kaljenje u vakuumu, tri visoko temperaturna popuštanja) i dubokim hlađenjem (kaljenje u vakuumu, duboko hlađenje u tekućem dušiku, visoko temperaturno popuštanje). Kod pojedinih stanja provedeno je i nitriranje u plazmi ionizirajućih plinova. Na tako pripremljenu podlogu nanesena je TiAN prevlaka PVD postupkom. Detaljna karakterizacija mikrostrukture provedena je "field emmission" skenirajućim elektronskim mikroskopom (FE SEM), transmisijskim elektronskim mikroskopom (TEM), rendgenskom difrakcijom (XRD). Mikro analiza kemijskog sastava pojedinih faza ispitana je EDS metodom te je EBSD metodom provedena mikrostrukturno - kristalografska analiza faza. TiAlN prevlaka je uz prethodno navedene metode ispitana još i fokusiranim snopom iona (FIB). Ispitana je otpornost na adhezijsko trošenje određivanjem kritičnih sila metodom rastućeg opterećenja, otpornost na suho klizno trošenje metodom "kuglica na ploči", otpornost na mikroabraziju metodom utiskivanja kuglice. Prionjivost prevlake ispitana je brazdanjem, metodom utiskivanja kuglice , Rockwellovom metodom utiskivanja indentora te određivanjem sile probijanja prevlake metodom "kuglica na ploči". Provedeno je i ispitivanje obradivosti jednoreznim alatom (alatom s jednom glavnom oštricom) tzv. "machinability test". Provedeno je pet serija kontinuiranog ispitivanja trošenja tokarenjem te su snimljene krivulje trošenja prekidanjem obrade svake 2min. Promatrani parametar trošenja alata bio je trošenje stražnje površine, VB, mm , a istrošena površina analizirana je na SEM-u. Provedena ispitivanja pokazala su da su mikrostrukture dobivene dubokim hlađenjem i nitriranjem utjecale na povećanje otpornosti na trošenje brzoreznog čelika PM S390 MC. Utvrđen je i njihov utjecaj na prionjivost TiAlN prevlake što je rezultiralo povećanjem otpornosti na trošenje uzoraka pri laboratorijskim ispitivanjima, kao i povećanje otpornosti na trošenje reznih pločica pri ispitivanju tokarenjem.

Abstract

This doctoral thesis deals with the study of the impact of microstructure on the tribological properties of high speed steel and the cutting tools made of high speed steel coated by TiAlN coating. The tested high speed steel was obtained by the powder metallurgy marked as Böhler PM S390 MC. Different microstructure conditions of this steel were obtained by heat treatment in two ways: conventional (vacuum hardening, three high-temperature temperings) and deep cooling (vacuum hardening, deep cryogenic treatment, high-temperature tempering). In some conditions nitrating in plasma of ionising gases was also carried out. The TiAlN coating was then applied to the surface prepared in this way, by means of the PVD (Physical Vapour Deposition) process. Detailed characterization of the microstructure was carried out by Field Emission Scanning Electron Microscope (FE SEM), Transmission Electron Microscope (TEM), X-Ray Diffraction (XRD). Micro analysis of the chemical composition of certain phases was studied by the EDS (Energy Dispersive x-ray Spectroscopy) method, and EBSD (Electron Backscatter Diffraction) method was used to carry out the microstructure - crystallographic analysis of phases. Apart from the previously mentioned methods, the TiAlN coating was studied using the Focused Ion Beam (FIB) as well. The study also included the resistance to galling by determining the critical forces using the load scanning test, resistance to dry sliding wear using the ball-on-flat method, resistance to micro-abrasion by means of the kalotest method. The coating adhesion was tested by the scratch test, kalotest method, Rockwell indenter method and by determining the coating penetration force using the ball-on-flat method. The machinability was also tested using single-point cutting tool machinability test. Five series of continuous testing of lathe wear were carried out, and the wear curves were recorded by interrupting the treatment every 2 minutes. The observed tool wear parameter was the wear of the back surface, VB, mm, and the worn surface was analysed by means of SEM. The carried out tests showed that the microstructures obtained by deep cooling and nitrating resulted in an increase of wear resistance of high speed steel PM S390 MC. Their influence was also determined regarding the adherability of TiAlN coating which resulted in improved wear resistance of samples in laboratory tests, as well as greater wear resistance of cutting inserts in lathe tests.

Item Type: Thesis (Doctoral thesis)
Uncontrolled Keywords: brzorezni čelik; rezni alati; otpornost na trošenje; duboko hlađenje; TiAlN prevlaka
Keywords (Croatian): high speed steel; cutting tools; wear resistance; deep cryogenic treatment; tialn pvd coating
Date Deposited: 22 Sep 2014 18:00
Last Modified: 16 Oct 2015 13:06
URI: http://repozitorij.fsb.hr/id/eprint/1482

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