J. Kadlec

Influencing properties of high-speed cutting steel, ion-nitrided and subsequently coated

Abstract Samples of high-speed cutting steel, vacuum heat treated and ion-nitrided in various nitriding agents, showed in the layer different phase-compositions. With short-time nitridation the layer was formed by intermetallic compound Fe 4 N, and with long-time nitridation by multiphase layer containing Fe 4 N, Fe 2.5 N and Fe 3 N. Layer microhardness after short-time nitridation was 1532 HV 0.05 and with long-time nitridation, where layer was thicker, it was only 1037 HV 0.05. A part of samples treated by ion-nitridation and even without it, was TiN coated with 2 μm thickness. Coating adhesion on the monophase layer was almost equivalent to the original surface with TiN coating, while in the multiphase layer adhesion was insufficient. By TiN coating the wear of high-speed cutting steel was significantly moderated and further improvement was attained by combination of ion-nitrided layer with subsequent coating. With wear tests the thickness of ion-nitrided layer had a more significant influence than coating adhesion to the layer. By coating treatment at temperature of 550°C in a vacuum, significant diffusion of iron into the layer was proved. From the beginning the diffusion proceeds faster, and after occupying free places it slows down, which was verified in the time from 10 minutes to 10 hours.

Laser-deposited thin films of biocompatible ceramic

Thin films of biocompatible materials such as hydroxylapatite (HA) - Ca10 (PO4)6(OH)2 were deposited by laser ablation technique. The films of HA were created on Ti substrates by KrF laser. The layers were deposited in vacuum, in pure H2O vapors (pressure 2 X 10-3 mbar - 2 X 10-1 mbar), and in Ar/H2O vapor mixture. Influence of laser energy density ET (3 Jcm-2, 13 Jcm-2) and substrate temperature Tg (500 degree(s)C - 760 degree(s)C) on the film parameters was studied. Two different technological processes were used for HA target preparation. Films and targets were characterized by Rutherford backscattering analysis (RBS), particle induced x-ray emission (PIXE), x-ray diffraction (XRD), scanning electron microscopy (SEM) and by Knoop microhardness and scratch test. The best crystalline HA films were reached in the mixture of Ar/H2O. Higher Tg had to be used for such deposition. Higher Tg was also preferable from the point of film microhardness. Adhesion of films to the substrates in the range of tens of Newtons was measured. The preliminary results of in vitro experiments of films biotolerance and resorbability are also presented.

Increasing of Durability of Surfaces by Plasma Nitriding Process

This article deals with properties of plasma nitrided layers in depth. The redistribution of alloy elements and C-N in depth of nitrided layers was analysed. The plasma nitriding process was used for creation of nitrided layers [1]. The nitrided layers were applied to 32CrMoV12-10 steel used for stressed machine parts. Samples were subsequently evaluated by metallographic, OES, hardness and microhardness methods. The results of measurement showed connection between chemical composition of alloying elements after chemical-heat treated process and universal hardness, microhardness.

Characteristics of Duplex Treated AISI 304 Stainless Steel

The duplex treatment consisted of a plasma nitriding at 470 °C for 4 h and subsequent coating with TiN layer was applied on AISI 304L stainless steel. The article is concerned to a study of the chemical composition and mechanical properties of duplex system. GDOES method, laser confocal microscopy, nanohardness and indentation test were employed to characterize the chemical composition, depth profiles, surface morphology, hardness, adhesion. The results show that the duplex surface system possesses a desirable combination of properties especially hardness. Adhesion of PVD coating was increased on nitrided surface.

Electrochemical Deposition of Hydroxyapatite and Hydroxyapatite/Ag Composite Coatings on Titanium Alloy Surface

The described technology makes possible to create hydroxyapatite (HA) nanostructures of various morphology and to create HA nanostructures with Ag particles of various shape, size and frequency. These nanostructures are due to their biocompatibility and potential antibacterial behaviour applicable as surface treatment of dental and other type of implants.

Characteristics of Duplex Coating on Austenitic Stainless Steel

The aim of the article is describe duplex treatment of austenitic stainless steel X12CrNi 18 8 surface. Combination of both plasma nitriding and PVD coating by TiN/TiCN as a surface treatment has been used to improve material hardness and wear resistance without decreasing corrosion resistance. GDOES, confocal microscopy, microhardness, indentation test were applied to characterize the chemical composition, surface morphology, adhesion and hardness of duplex treated specimens.

Plasma Treatment of Stainless Steel Surface

Described technology of stainless steel surfaces treatment is based upon the plasma nitridation of the component in micropulse plasma when nitridation atmosphere with a significant amount of methane is used. The process is performed so that a layer of iron and othet chemical element carbonitride may be formed on the surface of nitrided components. The formed layer is characterized by very good mechanical properties, e.g. an excellent abrasion resistence, a low friction coefficient and. high layer hardness.

Influence of crystallinity on bio- physical properties of hydroxyapatite films

Crystalline and amorphous hydroxyapatite (HA) films were prepared by KrF pulsed laser deposition method. Influence of HA structure on biomedical properties was studied. Crystallinity, morphology, composition, optical transmission and mechanical properties (adhesion) were measured. Biomedical properties were tested using human dermal fibroblast. The specific proteins (vimentin, fibronectin, pankeratin, keratin 14) were visualized. The worst proliferation of fibroblasts was observed on the amorphous coating, whereas the adhesion was well comparable with other surfaces. The level of keratinocyte differentiation on the amorphous and crystalline HA coating was the same. Results reached on physical and mechanical properties are discussed in connection with results of in vitro tests.

Study of thin TiCxN1-x films fabricated by hybrid magnetron-laser deposition

Titanium- carbonitride thin films were grown at room temperature using a hybrid deposition arrangement combining DC magnetron sputtering and KrF pulsed laser deposition (MSPLD). Carbon and titanium were simultaneously deposited on the same Si substrate, dimensions of 3 cm × 3 cm. Films were fabricated in argon- nitrogen atmosphere of 1 Pa - 5 Pa, for laser fluence of 15 Jcm-2 and magnetron power of 150 W. Film properties were modified by RF discharge held between the target and substrate. Film crystallinity was studied by XRD and the composition depth profile of TiCN layers by glow discharge optical emission spectroscopy (GDOES).

Study of titanium-carbon gradient layers grown by combination of laser deposition and magnetron sputtering

Gradient titanium- carbon films were grown by hybrid deposition arrangement combining laser deposition and DC magnetron sputtering. Laser was used for deposition of carbon films and magnetron simultaneously sputtered Ti on the same substrate. Depth profile of carbon and nitrogen species, films adhesion and microhardness are studied in connection with deposition conditions.