Priidu Peetsalu

Metallic powders produced by the disintegrator technology

The paper deals with the peculiarities of disintegrator milling, the development of disintegrator milling systems and the grindability of different metallic materials. In the first part of the paper the size reduction by collision is under consideration. A theoretical model for the size reduction of ductile materials by collision is proposed. The second part of the paper is focused on the development of disintegrators for processing of materials, which differs significantly from the other grinding equipment. The third part of the paper is focused on the disintegrator milling technology used for mechanical treatment of different metallic materials.

Evaluation of Residual Stresses in PVD Coatings by means of Tubular Substrate Length Variation

The aim of the study was to determine macroscopic residual stresses in PVD coatings. The device for measurement of the length of the substrate was improved, where a change in tube length was reduced to the deflection of the middle cross-section of the elastic element whose deformation was measured by four strain gauges. The formulas for calculation of residual stresses are presented. For comparison a unilateral coating was deposited on a vertically fixed plate using the conventional curvature method. As an application, residual stresses in hard PVD TiAlN coatings were investigated. The microstructure and thickness of the studied coatings were investigated by means of scanning electron microscopy (SEM) in Zeiss EVO MA-15. The mean values of compressive residual stresses determined by both methods, for the studied coatings, were very high (3.1-6.5 GPa), irrespective of coating thickness, and practically equal with the measurement uncertainty of the method. The developed tube length variation method is reliable and applicable for determination of residual stresses in PVD coatings. Introduction Physical Vapour Deposition (PVD) coatings are used inter alia for blanking, punching and cutting applications and can be deposited both on plain and more complex surfaces [1, 2]. It is wellknown that residual stresses arising in coatings during the deposition process have an important effect on the service life of the coating through influencing its mechanical and tribological properties and adhesion. The aim of the study was to determine macroscopic residual stresses in coatings vapoured on a vertically fixed cylindrical surface, using the deformation method, through measurement of the longitudinal length variation of the thin-walled tube, as well as to validate the results obtained with the conventional curvature method using the plate as the substrate. One batch of vertically fixed plates was prepared by depositing a unilateral coating on the front surface and the other batch of plates, by depositing it on the back surface. Thus a considerable amount of the vapoured target material was deposited on the fixing device as well [3]. On the other hand, using the tubular substrate, most of the coating was deposited on the outer surface of the tube (a small part of the coating was deposited on the nozzle) it is possible to estimate the values of residual stresses in coatings on cylindrical surfaces (e.g. cutting tools [4]). The measuring device for determination of the longitudinal length change of the substrate was improved (Fig. 3), where tube length variation was reduced to the deflection of the middle crosssection of the elastic element whose deformation was measured by four strain gauges [5]. As an example of application, residual stresses were measured in hard PVD TiAlN coatings which are Residual Stresses 2018 – ECRS-10 Materials Research Forum LLC Materials Research Proceedings 6 (2018) 131-136 doi: http://dx.doi.org/10.21741/9781945291890-21 132 most widely used for cutting tools [4]. Also the microstructure and thickness of the studied coating were investigated by means of scanning electron microscopy. Evaluation of Residual Stresses in the Coating Plates (Fig. 1b) are only deposited from one side and should be placed gripped with a claw in the fixing device made of carbon steel [3]. Depending on the deflection of the plate, modified Stoney’s formula will account for biaxial stresses [6]. In order to prevent deposition of the coating on the cross-section of the tube ends, they were closed by the nozzle (Fig. 1a); at the same time, the tube was vertically fixed, by the lower nozzle, to the rotary table of the chamber and was simultaneously rotated around its axis. a)

Evaluation of Residual Stresses in PVD Coatings by Means of Strip Substrate Length Variation and Curvature Method of Plate Substrate

The aim of the study was to determine macroscopic residual stresses in Physical Vapor Deposits (PVD) coatings through measurement of the length variation of the strip substrates coated on both sides. The length change of the strip was reduced to the deflection of the middle cross-section of the elastic element and was recorded by four strain gauges. For validating the obtained results, the conventional curvature method was used. As an application, residual stresses in hard AlCrN PVD coatings were investigated. The coatings were nanolayered to achieve better coating toughness for blanking and punching applications. The steel strips and steel plates with two thicknesses were used as the substrate. The values of the compressive residual stresses, determined by both methods for the investigated coatings, were very high (3.3 -3.6 GPa) independent of coating thickness and practically equal within the measurement uncertainty of the method. Good agreement between the experimental results obtained with both methods suggests that the presented method, strip length variation, is applicable for determination of residual stresses in coatings. Compressive stresses in coatings are desirable as they strengthen the coating.

Cyclic Loading of TiCN Coating by Vickers Indentation

Physical Vapour Deposited (PVD) coatings are used in wide range of industrial applications where requirements differ. For example, in cutting applications adhesive-abrasive wear along with high contact stresses prevail and PVD coating with thickness of ~2 μm are used. In forming applications adhesive wear usually dominates and relatively thick PVD coatings (~5 μm) are preferred. For both the applications coatings are subjected to cyclic stress and therefore it is a point of interest to learn the behaviour of PVD coatings with different thickness under cyclic loading. Cracking resistance and fatigue properties of gradient TiCN on hard metal substrate was evaluated by means of the cyclic Vickers indentation method. Hard metal was chosen as a substrate material to avoid pile-up effect and support the hard coating during indentation. The results of the single indentation Vickers test show that secondary radial and circumferential cracks appear in tested coatings already after the first indent. With increasing cycles the cracks grow up to a critical crack length after which the crack length doesn’t increase further. The tested coating thickness has no significant effect on cracking behaviour.

Evaluation of Residual Stresses in PVD Coatings by Means of the Curvature Method of Plate

Physical Vapor Deposition (PVD) coatings are primarily designed for metal cutting tools operating in extreme machining and blanking conditions. Residual stresses arising during coating deposition exert an important effect on the service life of the coating through influencing mechanical and tribological properties and adhesion. To determine macroscopic residual stresses, the conventional curvature method was used. As an application, residual stresses in four aluminum based PVD hard coatings, i.e. AlTiN, AlTiSiN, AlCrN, and AlCrSiN, were investigated in the presence of the Ti adhesion layer. Nickel steel plates and steel plates were used as the substrate. Residual stresses were compressive and high (3.0-7.5 GPa) in all coatings. Compressive stresses in coatings are desirable in cohesive tool damage as they strengthen the coating. The values of residual stresses were not significantly dependent on the angle of plate placement (parallel (0°), inclined (45°) and perpendicular (90°)) in relation to the PVD cathode in the deposition chamber. The magnitude of residual stresses is influenced by intrinsic strain at layer growth rather than by thermal stress.

Deformation-Burst Schemes of 3-Piece Aerosol Containers

This paper focuses on a three-piece steel aerosol container deformation and burst pressure comparison and tries to point out some topics which could help to improve pressure resistance of an aerosol container. Different material thicknesses are tested to find out which one could improve the overall aerosol container performance the most. This research shows that thinner material can give satisfying pressure resistance results what is important when trying to reduce material costs but further research will be needed to get necessary knowledge of deformation-burst schemes in depth.

Effect of Hot Dip Galvanizing on the Mechanical Properties of High Strength Steels

Present study focuses on investigating the hot dip galvanizing effect on the mechanical properties of high strength steel. The effect of chemical pre-treatment (hydrogen diffusion) and the effect of hot dip galvanizing temperature on mechanical properties was studied with high strength steel S650MC. Additional tests were made with widely used structural steel S355J2. A batch type hot dip galvanizing process was used and zinc bath temperature was 450 °C and 550 °C. Results of the study show the behaviour of high strength steel during hot dip galvanizing process.