Otpornost na trošenje ventila parne turbine

scientific master's theses

• Title (english): Wear resistance of steam turbine valve
• Author: Gordana Ribarić
• Mentor: Vinko Ivušić (mentor)
• Committee member: Slobodan Kralj (predsjednik povjerenstva)
• Committee member: Vinko Ivušić (član povjerenstva)
• Committee member: Branko Staniša (član povjerenstva)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2005-10-01, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering
• Universal decimal classification (UDC): 621 - Mechanical engineering. Nuclear technology. Machinery

Abstract

Regulacijski parorazvodni ventil parne turbine u svom radu tj. funkcijskom gibanju opterećen je visokim temperaturama (θmax=535°C) i tlakom pregrijane pare (pmax=150 bar), te trošenju dijelova pozicija koje su površinski oplemenjene. Na ventilu je uočeno 7 triboparova s različitim tipovima trošenja(sklizno, udarno, abrazijsko, erozijsko trošenje i izjedanje( freeting). Svrha i cilj rada odabir je optimalnih rješenja tj.triboloških mjera izbora osnovnog materijala i postupaka oplemenjivanja površina na dijelovima ventila koji čine triboparove. U praktičnom dijelu rada su izvršena ispitivanja trošenja na abrazijsko, erozijsko i adhezijsko trošenje površinski oplemenjenih uzoraka od čelika 21CrMoV57 i X22CrMoV121. Primjenjeni su slijedeći postupci oplemenjivanja površina: ionitriranje, tvrdo REL navarivanje, tvrdo plazma navarivanje s prelaznim lukom te tvrdo JET KOTE naštrcavanje koje spada u grupu HVOF postupaka (High velocity oxy fuel spraying -naštrcavanje nadzvučnim brzinama u struji gorivog plina s kisikom). Tvrda navarivanja i naštrcavanja izvedena su s dodatnim materijalom na osnovi kobalta s karbidima (Stelit 6 sastava Co-28Cr-4W-1C). Izvršena su i mjerenja mikrotvrdoće te metalografska analiza. Rezultati ispitivanja pokazuju da najbolju otpornost na abrazijsko trošenje imaju ionitrirani uzorci, na erozijsko trošenje REL tvrdo navareni uzorci, a na adhezijsko trošenje plazma navareni uzorci. Utvrđeno je da osnovni materijal značajno utječe na mikrotvrdoću i otpornost trošenju oplemenjenih površina.

Abstract (english)

Regulating valve on steam turbine in its workings (in functional moving) is subjected to high temperatures (θmax=535°C) , high steam pressures (pmax=150 bar) and is exposed to wear on the position parts which have been surface treated.There are 7 tribopairs on each regulating valve with various observed types of wearing –adhesion, erosion, impact, fretting and abrasion wear. The purpose of this work is the selection of optimal tribological solutions – selection of base metal and tribologic protection methods on the position parts of the regulating valve tribopairs. In practical part of this work, tribologic laboratic examinations (adhesive, abrasive and erosions tests) are performed on samples of steel 21CrMoV57 and X22CrMoV121 which have been surface protected. The following protection procedures were applied - plasma nitriding, SMAW hardfacing, PTA (plasma transferred arc) hardfacing and hard spraying by JET KOTE , which belongs to HVOF spraying (High velocity oxy fuel spraying). Hardfacing and hard spraying are done with consumables of Co-base with carbides – Stellite 6 with nominal chemical composition Co-28Cr-4W-1C. Microhardness examinations and metalografic analysis are also done. Testing results show that the best resistance to abrasive wear is obtained by plasma nitriding , to erosion wear by SMAW hardfacing and to adhesion by PTA hardfacing. It can be seen that basic material has a signitific effect on microhardness and wear resistance of the surfaces treated.

• Keywords: regulacijski ventili; trošenje; tvrdo navarivanje; Stellite 6; ionitriranje; JET KOTE
• Keywords (english): regulating valves; wear; hardfacing; Stellite 6; plasma nitriding; JET KOTE
• Language: croatian
• URN:NBN: urn:nbn:hr:235:246640
• Study programme: Title: Mechanical Engineering - mr.sc.; Study programme type: university; Study level: postgraduate; Academic / professional title: magistar znanosti (magistar znanosti)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Closed access
• Created on: 2020-12-28 13:13:18