Title: Effect of different coatings on thermal fatigue behaviour of AISI H11 hot work tool steel

Authors: M. Faccoli, G.M. La Vecchia, R. Roberti, A. Molinari, M. Pellizzari

Addresses: Department of Mechanical Engineering, University of Brescia, Brescia, Italy. Department of Mechanical Engineering, University of Brescia, Brescia, Italy. Department of Mechanical Engineering, University of Brescia, Brescia, Italy. Department of Materials Engineering, University of Trento, Trento, Italy. Department of Materials Engineering, University of Trento, Trento, Italy

Abstract: The improvement in wear and corrosion resistance induced by vapour-deposited coatings whether chemical (CVD) or physical (PVD) are well-known. In fact, when the applied coating is thick enough, it tends to be essentially pore free and dense providing an excellent barrier protection both in terms of corrosion and wear resistance. A typical application area for vapour-deposited coatings on ferrous alloys is the surface modification given by TiN or TiC PVD coatings to improve the service life of high speed steels used for manufacturing cutting tools. As a surface modification technique, PVD is attractive because the different procedures proposed in the literature and industrially developed allow coatings to be obtained of controlled composition and strength thus making possible the extended use of coated tools for wider application fields such as the die-casting process in which die casting dies must withstand thermal shock, thermal fatigue and resistance to molten metals. In the present paper, both nucleation and propagation of fatigue cracks induced by thermal fatigue cycling on AISI H11 hot work tool steel PVD coated with chromium nitride and titanium/aluminium nitride have been investigated. A further coating given by a dense film of magnetite (Fe₃O₄), employed as corrosion barrier and obtained by surface oxidation of the same AISI H11 hot work tool steel, has also been studied. The obtained thermal fatigue results have been compared with previous data from tests on the same uncoated steel and have been related to the morphology, chemical composition and physical proprieties of the tested coatings.

Keywords: coatings; vapour deposition; thermal fatigue; AISI H11 hot work tool steel.

DOI: 10.1504/IJMPT.2000.001235

International Journal of Materials and Product Technology, 2000 Vol.15 No.1/2, pp.49-62

Published online: 01 Jul 2003 *

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