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  • RMZ-M&G, Vol. 56, No. 3 pp. 254388 (2009)Ljubljana, September 2009

    ISSN 1408-7073

    PERIODICAL FOR MINING, METALLURGY AND GEOLOGY

    RMZ MATERIALI IN GEOOKOLJEREVIJA ZA RUDARSTVO, METALURGIJO IN GEOLOGIJO

  • II Historical Review

    RMZ-M&G 2009, 56

    Historical Rewiev

    This year University of Ljubljana marks its 90th anniversary. Technical fields were joint in the School of Engineering that included the Geologic and Mining Division while the Metallurgy Division was established in 1939 only. Today the Departments of Geology, Mining and Geotechnology, Materials and Metallurgy are part of the Faculty of Natural Sciences and Engineering, University of Ljubljana.

    Before War II the members of the Mining Section together with the Association of Yugoslav Mining and Metallurgy Engineers began to publish the summaries of their research and studies in their technical periodical Rudarski zbornik (Mining Proceed-ings). Three volumes of Rudarski zbornik (1937, 1938 and 1939) were published. The War interrupted the publi cation and not untill 1952 the first number of the new journal Rudarsko-metalurki zbornik - RMZ (Mining and Metallurgy Quarterly) has been pub-lished by the Division of Mining and Metallurgy, University of Ljubljana. Later the journal has been regularly published quarterly by the Departments of Geology, Mining and Geotechnology, Materials and Metal lurgy, and the Institute for Mining, Geotech-nology and Environment.

    On the meeting of the Advisory and the Editorial Board on May 22nd 1998 Rudarsko-metalurki zbornik has been renamed into RMZ - Materials and Geoenvironment (RMZ -Materiali in Geookolje) or shortly RMZ - M&G.

    RMZ - M&G is managed by an international advisory and editorial board and is ex-changed with other world-known periodicals. All the papers are reviewed by the cor-responding pro fessionals and experts.

    RMZ - M&G is the only scientific and professional periodical in Slovenia, which is pub-lished in the same form nearly 60 years. It incorporates the scientific and professional topics in geology, mining, and geotechnology, in materials and in metallurgy.

    The wide range of topics inside the geosciences are wellcome to be published in the RMZ -Materials and Geoenvironment. Research results in geology, hydrogeology, min-ing, geotechnology, materials, metallurgy, natural and antropogenic pollution of envi-ronment, biogeochemistry are proposed fields of work which the journal will handle. RMZ - M&G is co-issued and co-financed by the Faculty of Natural Sciences and Engi-neering Ljubljana, and the Institute for Mining, Geotechnology and Environment Lju-bljana. In addition it is financially supported also by the Slovenian Research Agency, Science and Technology of Republic of Slovenia.

    Editor in chief

  • IIITable of Contents Kazalo

    RMZ-M&G 2009, 56

    Table of Contents Kazalo

    Original Scientific Papers Izvirni znanstveni lanki

    Laser cladding in the use effects on nitrided and PVD coated steels used for die-casting using various process parameters and techniques 254

    Pojavi pri laserskem navarjanju nitriranih in PVD prevleenih jekel za orodja za tlano litje z uporabo razlinih parametrov in tehnik BomBa, D., Fazarinc, m., Pleterski, m., tuek, J., muhi, t.

    Characterisation of solid airborne particles in urban snow deposits from Ljubljana by means of SEM/EDS 266

    Opredelitev trdnih zranih delcev v snenem depozitu iz urbanega obmoja Ljubljane s SEM/EDS

    miler, m., Gosar, m.

    Aspects of structures and depositional environment of sand bodies within tomboy field, offshore western Niger Delta, Nigeria 284

    Znailnosti struktur in okolja odlaganja peenih teles v obmoju Tomboyja, priobalna delta Zahodnega Nigra, Nigerija

    nton, m. e., aDesina, a. D.

    Mineral Policy in the Era of Sustainable Development: historical context and future content 304

    Rudarska politika v asu trajnostnega razvoja: zgodovinski kontekst in vsebine prihodnosti

    olar, s. V., shielDs, D. J., miller, m. D.

    The error estimation in the prediction of ultimate drift of RC columns for performance-based earthquake engineering 322

    Ocena napake pri napovedovanju mejne premaknitve AB-stebrov v potresnem inenirstvu Peru, i., Dolek, m.

  • IV Table of Contents Kazalo

    RMZ-M&G 2009, 56

    Preliminary Notes Predhodne objave

    Extra machinability modeling 338Modeliranje poveane obdelovalnostikoVai, m., Peninik, m.

    Environmental labelling of products with type I labels 346Ekoloko oznaevanje proizvodov z oznakami tipa I crnoBrnJa, B., BuDak, i., ili, m., hoDoli, J.

    Professional Papers Strokovni lanki

    Heat Treatment of Cold Formed Steel Forgings 356Toplotna obdelava hladno preoblikovanih jeklenih odkovkovkosec, B., BreziGar, m., kosec, G., eVnik, G., BizJak, m.

    Optimiranje delovanja glavnih ventilatorjev v asu mirovanja jame 364Optimisation of mine ventilators operation in conditions of stagnation the pitsaloBir, B.

    Author`s Index, Vol. 56, No. 3 374

    Instructions to Authors 376

    Template 383

  • 254RMZ Materials and Geoenvironment, Vol. 56, No. 3, pp. 254264, 2009

    Original scientific paper

    Laser cladding in the use effects on nitrided and PVD coated steels used for die-casting using various process parameters and

    techniques

    Pojavi pri laserskem navarjanju nitriranih in PVD prevleenih jekel za orodja za tlano litje z uporabo razlinih parametrov in

    tehnik

    D. BomBa1, *, m. Fazarinc1, m. Pleterski2, J. tuek2, t. muhi3

    1University of Ljubljana, Faculty of Natural Sciences and Engineering, Akereva cesta 12, SI-1000 Ljubljana, Slovenija

    2University of Ljubljana, Faculty of Mechanical Engineering, Akereva cesta 6,SI-1000 Ljubljana, Slovenija

    3TKC, d. o. o., Trnovska 8, SI-1000 Ljubljana, Slovenija

    *Corresponding author. E-mail: david.bombac@ntf.uni-lj.si

    Received: March 30, 2009 Accepted: May 15, 2009

    Abstract: Repair welding of die-casting tools is approach to extend life cycle of expensive dies. Issues addressed in this paper are problems emerging from repair welding of surface treated steels e.g. nitriding, oxidizing, hard coating or duplex-treating. Cladding tests were car-ried out on various gas nitrided and oxidized or hard coated chrome martempered steel used for die tools. Observed welding defects were extensive hot cracking and copious formation of gas pores. For duplex-treated surfaces a procedure with preceding laser remelting and laser welding is proposed. Minimized negative effects of the base and welded material were found.

    Izvleek: Reparaturno varjenje je postopek za podaljanje trajnostne dobe dragih orodij za tlano litje. V lanku so obravnavani problemi, ki nastajajo pri reparaturnem varjenju povrinsko obdelanih jekel: ni-triranje, oksidiranje, prevleenje ali zaporedna povrinska obdelava z razlinimi procesi (na primer nitrirnanje in nato PVD prevleenje). Preizkusno varjenje je bilo izvedeno na razlinih plinsko nitriranih in oksidiranih ali prevleenih vzorcih iz kromovega maraging jekla

  • 255 BomBa, D., Fazarinc, m., Pleterski, m., tuek, J., muhi, t.

    RMZ-M&G 2009, 56

    za livarska orodja. Zaznane varilne napake so bile znatne razpoke in tevilne plinske pore. Za dvojno oplemenitene povrine je predlagan nov postopek varjenja s predhodnim pretaljevanjem. Ugotovljeno je bilo zmanjanje negativnih efektov podlage in varilnega materiala.

    Key words: laser cladding, repair welding, die-casting tool steel, nitrid-ing, oxidizing, PVD coating

    Kljune besede: lasersko navarjanje, reparaturno varjenje, jekla za orodja za tlano litje, nitriranje, oksidacija, PVD-prevleke

    damage are tension cracks caused by constructional notches, local adherence of a casting alloy and tool i.e. soldering, and steel erosion promoted by the cast molten metal or plastic flow.[5, 6] While moulds for plastic injection moulding are subjected to lower working temper-atures their pressure cycles are higher and therefore, mechanical fatigue dam-age and overload failures might occur. Life time for aluminium casting dies is usually 104 cycles.[7] Increasing de-mand for reduction of manufacturing costs dew to economical reasons re-quires the exploration of adaptable and reliable solutions for extending the life time of the dies using nitriding, oxidiz-ing, PVD coatings or various duplex treatments. Further extension of the life time of the dies is achieved with die repairing techniques such is surface welding.

    Nitrided die casting tools have a lot of advantages i.e. easier separation of a casted part and mould, less frequent

    Introduction

    Parts for automotive industry made from aluminium or plastic are usually casted or moulded. Casting dies are subjected to various complex impact and thermomechanical loads in their working environment. High stresses lead to a plastic deformation of the die during tools lifetime. Thus, it is re-quired that steels used for casting dies should have some properties such as resistance to high temperatures, ther-mal deformation, thermal shock dur-ing working processes, etc. Depending on a tool application, typical damage and failure mechanisms may differ. A thermal fatigue cracking is the most important life limiting failure mode in the tools for die-casting.[14] It is often observed on the tool surface as a net-work of fine cracks or as individual and clearly pronounced cracks. Formation of thermal fatigue cracks leads to loss of a surface material in form of small fragments. Other common reasons for

  • 256Laser cladding in the use effects on nitrided and PVD coated steels used for die-casting ...

    RMZ-M&G 2009, 56

    cleaning of the die-core system and in-crease of the service life for up t