Wpływ rodzaju umocnienia ceramicznego chromowych powłok ochronnych nakładanych plazmowo na ich zwilżalność szkłem

• Autorzy: Włosiński W. , Chmielewski T.

Warianty tytułu

EN

Influence of the type of ceramic reinforcement on the glass-wettability of composite chromium layers produced by plasma transfer arc method

• Języki publikacji: PL

Abstrakty

PL

Przedmiotem przedstawionych wyników badań są chromowe warstwy kompozytowe wykonywane metodą napawania plazmowego, przewidziane jako powłoki ochronne na formy do precyzyjnego prasowania lub wirowania szklą. Dzięki zastosowaniu chromu jako osnowy uzyskano wysoką odporność na utlenianie w wysokiej temperaturze, podwyższoną twardość (w stosunku do podłoża wykonanego ze stali 3H13) oraz stosunkowo niską zwilżalność szkłem. Umocnienie kompozytu cząstkami ceramicznymi (Al2O3 lub Cr3C2) ma na celu podwyższenie twardości, zwiększenie odporności na ścieranie i żaroodporności, a jednocześnie wpływa w istotnym stopniu na obniżenie zwilżalności szkłem badanych powłok. W artykule omówiono wyniki badań zwilżalności przez szkło powłok kompozytowych złożonych z Cr-t-AI2O3 lub Cr+Cr3C2.

EN

The experiments were concerned with composite chromium layers produced by the plasma transfer arc method (PTA), intended for use as protective coatings formed on tools for precision forming of glass. Thanks to the use of chromium as the coating matrix, the coatings are highly resistant to oxidation at high temperature, show an increased hardness (greater than that of the 3H13 steel substrates) and are relatively slightly wetted by glass. The composite material was reinforced with ceramic particles (Al2O3 or Cr3C2) with the aim to increase its hardness, frictional wear resistance and heat resistance. The reinforcement also appears to reduce essentially the wettability of the coating by glass. The paper discusses the results of examinations of the glass-wettability of the Cr+Al2O3 or Cr+Cr3C2 composite coatings. Glass industry knows several methods of fabricating protective coatings to cover the working surfaces of glass forming tools. The choice of an appropriate method depends on the requirements set for a given coating. In the process of hot forming (600:700°C) of glass, it is required that the tools not only shape the product to the specified geometry but also that they ensure its appropriate cooling to below the glass softening temperature during a specified period of time so as to avoid generating thermal stresses and, thus, cracking, deformation and shape changes. The tools intended for shaping glass products should not only be strongly resistant to oxidation at high temperature but also have a good thermal conductivity and reduced wettability by liquid glass. The 'fidelity' of copying the forming tool shape by the glass batch being formed and the heat transfer to the tool both strongly depend on how the working surface of the tool is wetted by the glass. The wettability also determines the highest permissible temperature of the forming process. In order to prevent the glass from adhering to the tool surface, the wettability of the tool coating should be reduced. The reduced glass wetting of the coatings described in the present paper was achieved thanks to the use of chromium as the coating matrix material. This is so since a thin, tightly adhering oxide film forms on the chromium surface. According to the literature [6], this film shows a low wettability since most often it forms an equilibrium system with the wetting liquid phase and, thus, it does not form solutions or other new phases with it. The results shown in Figure 8 suggest that the wettability of the chromium coating by kinescope-type glass can greatly be reduced by introducing a ceramic phase into it. It can also be seen from this figure that the wettability of the coating can further be reduced by increasing the amount of the reinforcing CrxCy carbide phase (coatings No 1 and 2), and that the use of another reinforcing constituent, namely Al2O3, in small amounts comparable with those added to coating No 1, decreases the wettability even more. Hence we can see that Al2O3 decreases the wetting angle more effectively than chromium carbides. The immediate advantages of the reduced glass wettability of the protective coatings formed on glass forming tools are: - reduction of the glass adherence to the tool surface during the glass forming process, and - possibility of reducing the glass forming temperature so as to increase its flowability.

Słowa kluczowe

PL

kompozyty; warstwa kompozytowa; powłoka chromowa; nakładanie plazmowe

EN

composites; composite chromium layers; plasma transfer arc method

• Wydawca: Wydawnictwo Politechniki Częstochowskiej
• Czasopismo: Kompozyty
• Rocznik: 2002
• Tom: R. 2, nr 5
• Strony: 348--353
• Opis fizyczny: Bibliogr. 6 poz., tab., wykr., rys.

Twórcy

autor

Włosiński W.

• Politechnika Warszawska, Instytut Technologii Materiałowych, ul. Narbutta 85, 02-542 Warszawa

autor

Chmielewski T.

• Politechnika Warszawska, Instytut Technologii Materiałowych, ul. Narbutta 85, 02-542 Warszawa

Bibliografia

• [1] Przywóski A., Socha J., Doliński A., Nakonieczny A., Galwaniczne powłoki stopowe nikiel-wolfram jako warstwy ochronne stempli do tłoczenia szklanych ekranów TVC, Inżynieria Powierzchni 2000, 3.
• [2] Iwamoto N., Fundamentals of ceramic (glass)-metal bounding, Trans. of JWRJ 1979, 8, 2.
• [3] Iwamoto N., Makino Y., Miyata H., Joining of silicon carbide using Ni-ZrH2 powder mixture, Trans. of JWRJ 1986, 16, 1.
• [4] Wyatt O.H., Dew-Hughes D., Metals, Ceramics, and Polymers, Cambridge University Press, Cambridge 1974
• [5] Włosiński W., Chmielewski T., Otrzymywanie kompozytów metalowo-ceramicznych metodami plazmowymi, Kompozyty (Composites) 2001, 1, 1, 7-12.
• [6] Senkara J., Windyga A., Podstawy teorii procesów spajania, Wydawnictwa Politechniki Warszawskiej, Warszawa 1990.