Daniel Kottfer

TRIBOLOGICAL AND REFRACTORY PROPERTIES OF TiAl3 INTERMETALLIC ALLOY

Substrates of Ti-based coatings were investigated regarding wear resistance and refractoriness. Substrates with and without the TiAl3 coating formed by the ion plating method with evaporation of Al are considered. Additionally, the paper briefly presents principles of kinetics of the formation of the TiAl3 coating.

The Influence of the Bias on Mechanical Properties of a-C:H CVD Thin Films

This work was financially supported by the Slovak Grant Agency under the grant VEGA 1/0432/17.

HIGH-TEMPERATURE OXIDATION, MECHANICAL, AND TRIBOLOGICAL PROPERTIES OF ELECTROPLATED Cr COATING ON STEEL AFTER ANNEALING IN 700∘C

Although electroplated hard chromium coatings were extensively studied and applied in industry, the properties of the coatings after annealing at different temperatures were investigated insufficiently. In this work, the influence of heat treatment on the mechanical, tribological, and structural properties of chromium coating, electrochemically deposited on 38HN3MFA steel were investigated. A specific bath composition and deposition parameters were selected, which has been compared to the literature data. Parameter selections were based on data from military research industry and contain noticeably lower amount of sulfuric acid (1.2g/L), CrO3 (180g/L) and lower current density (25A/dm2). Coefficient of friction and coatings wear rate were measured by means of ball-on-disc method at the temperature of 30∘C, 200∘C, 500∘C, and 700∘C. The coefficient of friction has decreased from 0.71 for the temperature of 30∘C to the value of 0.5 for 700∘C due to the change of wear mechanism. Hardness of the as-received coating reaches the value of 11.4GPa and 9.5, 8.3, 6.4GPa for the samples after annealing in the temperature of 200∘C, 500∘C and 700∘C, respectively. The influence of heat treatment on structural properties of electroplated Cr coatings was studied by X-ray diffraction. Scratch test showed that layer is characterized by excellent adhesion with no adhesive rupture. Cr-coated 38HN3MFA steel exhibits reduced susceptibility to high-temperature degradation by 25%, basing on the mass lost measured at 900∘C.

Evaluation of Relationship between Cutting Parameters and Torque in Hole Making of Titanium Alloy

In terms of machinability are titanium alloys classified in the group of difficult to cut materials. The main factors determining this status are limited tool life, high generated cutting forces (torque) and temperature in cutting zone caused by low thermal conductivity as well as chemical reactivity with cutting tool. Solid carbide drills still remain as preferred choice in hole making process when machining Ti6Al4V alloy. Besides cutting conditions, tool and cutting edge geometry significantly affect the value of torque. Reduction of process energy requirements can be achieved by appropriate optimization of these parameters. Mathematical model describing influence of cutting speed, feed rate, clearance angle and cutting edge radius on investigated variable with high reliability coefficient (R2=96.72%) was found. Drilling experiments were designed and carried out using Taguchi orthogonal array L16.

Types of Tool Wear of AlTiN Coated Cutting Insert after Machining of Weld Overlay

Authors of the paper present different types of tool wear after machining of weld overlay with AlTiN cutting insert. Welded layer was created on roller made from S355J0 steel by Open Arc (OA) method also referred as Metal One Gas (MOG). Various forms of tool wear were documented by optical microscope. Microchipping of cutting edge, built up edge (BUE) and flank wear were identified on examined round insert in rough turning of hard cladding.