Materials Engineering - Materiálové inžinierstvo (MEMI)
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INTERACTION OF SUB-ZERO PROCESSED Cr-V LEDEBURITIC STEEL WITH ALUMINA, 100Cr6-STEEL AND BRONZE IN DRY SLIDING
Get PDFThe interaction of the Vanadis 6 steel, processed without/with an application of sub-zero treatment, with alumina (hard counterface), 100Cr6-ball bearing steel (counterface of an intermediate hardness) and CuSn6 (soft counterface) has been examined. Obtained results infer that the wear performance against alumina is the best for no-SZT material quenched from higher austenitizing temperature (highest hardness). In dry sliding against 100 Cr6 ball bearing steel, the best wear resistance has been achieved for the material after SZT at -196 oC/10 h. The interaction of Vanadis 6 steel with CuSn6 results in a considerable counterpart material transfer to the samples of Vanadis 6-steel whereas the extent of the transfer is rather independent on both the austenitizing temperature and the SZT parameters, within the range of parameters used for the investigations
Improvement of the wear behaviour of highly-loaded components and tools by multi-combined surface treatment
Get PDFThis paper introduces a novel multi-combined surface treatment consisting of the individual treatments of plasma nitriding (PN), physical vapour deposition (PVD) and electron beam hardening (EBH). Using graded surface layers produced by such a combined surface treatment, it is possible to withstand the complex load conditions incurred by components and tools. It is shown, that the treatment sequences PN+EBH+PVD and EBH+PN+PVD are suitable for improving material properties. These multi-combined surface treatments lead to a significant improvement in load-supporting capacity. Critical load values of cohesive failure measured by scratch tests are tripled when compared to the individual treatment of PVD, and increased by at least 20% in comparison to the duplex treatments of EBH+PVD or PN+PVD. The metallurgical compatibility of the single treatments is essential for the success of combined treatments. Material-specific limitations are defined, which exclude failure due to crack initiation, the occurrence of retained austenite, and tempering effects. Based on the model wear-test assembly block-on-cylinder, it was proved, that the specific wear rate of multi-combined treated specimens is reduced about 20-50% while wear of counterpart components is decreased as well. The triplex surface heat treatment introduced opens up new prospects for highly-loaded components and tools
Heat Treatment of Cr- and Cr-V ledeburitic tool steels
Get PDFCr- and Cr-V ledeburitic cold work tool steels belong to the most important tool materials for large series manufacturing. To enable high production stability, the tools must be heat treated before use. This overview paper brings a comprehensive study on the heat treatment of these materials, starting from the soft annealing and finishing with the tempering. Also, it describes the impact of any step of the heat treatment on the most important structural and mechanical characteristics, like the hardness, the toughness and the wear resistance. The widely used AIS D2- steel (conventionally manufactured) and Vanadis 6 (PM) are used as examples in most cases
DEGRADATION OF CZECHOSLOVAK CREEP RESISTANT STEELS AFTER 50 YEARS OF SERVICE
Get PDFThermally loaded assemblies in the energy and chemical industries require materials that provide the necessary functional characteristics, even after very long periods of operation. For the assessment of these materials are used expression grade of degradation in the basic meaning of the original English word grade = quality grade, Where the degradation is cumulative deterioration of quality (properties) and thereby reduce the utility value. Knowledge of these mechanisms acting simultaneously allows determining the boundary conditions and more efficient utilization of used materials. Alternatively, it may give information to a qualified estimate of the causes of failure. Degradation starts its own production of semi-finished products (purity, structural homogeneity) continues through technological factors of production (welding) and the last part of degradation is during service of the parts (corrosion, hydrogen embrittlement, etc.). The aim of this article is at bases information obtained from fifty years of degraded materials to obtain information for more accurate reference catalogue. This catalogue can on bases information obtained from the microstructure and hardness estimate the state of degradation or possible time to rupture for the material
34CrMo4 steel resistance against the SSC after controlled cooling process
Get PDFThe sulphide stress cracking corrosion resistance of 34CrMo4 steel after the accelerated cooling process under the Ar3 temperature was investigated. Two modes of heat treatment were applied to achieve homogeneous microstructure and at least partially eliminated segregation banding. First mode was based on the cooling up to the 420 °C on the air and subsequent cooling in the quenching bath. Second mode was similar except the temperature of cooling on the air, which was set up to the 460 °C. Afterward in both cases, the stress relief annealing was applied. Both modes of heat treatment resulted in the significantly banded microstructure based on the pearlite, ferrite and modified lower portion of accicular ferrite. The differences in mechanical properties of both cases of heat treatment were minimal. The SSC loading times to failure of both sets did not lead to important differences
Microstructural changes of AISI 316L due to structural sensitization and its influence on the fatigue properties
Get PDFMechanical and fatigue properties of material are dependent on its microstructure. The microstructure of AISI 316L stainless steel commonly used for the production of medical tools, equipment and implants can be easily influenced by its heat treatment. Microstructural changes and fatigue properties of AISI 316L stainless steel due to the heat treatment consisted of annealing at the temperature of 815°C with the dwell time of 500 hours were analyzed in the present paper. Precipitation of intermetallic phases and carbides was observed as a response of the material to the applied heat treatment. Small negative influence was observed in the case of fatigue region bellow 105 cycles; however the fatigue limit remains unchanged due to the structural sensitization
Influence of process parameters on torsional strength, impact toughness and hardness of dissimilar AISI 304 and AISI 1021 friction welded steels
Get PDFIn this present study an attempt was made to join austenitic stainless steel (AISI 304) with low alloy steel (AISI 1021) at different rotational speeds and at different axial pressures and then determining the strength of the joint by means of mechanical properties such as torsional strength, impact strength and micro hardness. The experimental results indicate that the rotational speed and the axial pressure have a significant effect on the mechanical properties of the joint and it is possible to improve the quality of the joint by selecting the optimum parameters
Investigation of possible causes for appearance of a crack in the welded joint of the ship winch frame
Get PDFShip winches are one of the most important parts of the ship equipment since they perform the most responsible tasks on various ships. In the majority of cases, the ship winches are welded structures. All the necessary calculations according to required standards, that have to be done prior to actual execution of the structure, should also include the verification by the finite elements method. For the high reliability requirements to be met, the welded joints integrity of all the parts must be examined before they are assembled into the winch. After all the tests are conducted and parts are assembled into the winch, the factory acceptance test (FAT) must be done. During those tests all the flaws, which can appear during manufacturing, must show. An appearance of a very unusual crack in the ship winch frame, which happened during the FAT, is described in this paper. The simulation by the finite elements method was performed to obtain the stresses at which the crack appeared. The possible causes for that crack appearance are considered. Some measures for reducing appearance of such cracks to a minimum are proposed, as well as certain directions for further research of this problem.
The impact of welding wire on the mechanical properties of welded joints
Get PDFThis paper presents results of the mechanical properties of Hardox 450 steel welded joints. These welded joints were made in accordance with welding procedure specifications (WPS), which was prepared and applied in the Wielton company. Fillers were provided by welding wires with two different diameters. The welding wire was G4Sil with diameter of 1.0 mm and 1.2 mm. The aim of this study was to examine whether the thickness of the welding wire has a direct effect on the properties of welded joints. Test specimens were made in similar parameters of the welding process. Then they were subjected to macroscopic research, tensile strength, impact strength and hardnes
ANALYSIS DEGRADATION OF POLYSTYRENE WITH MONTMORILLONITE NANOFILLERS
No full textThe paper is focused on the experimental investigation of the montmorillonite nanofillers effect on deformation properties of polystyrene KRASTEN 171. In some cases, combination of a low amount of clay with dispersed polymeric phase may cause synergistic effects leading to very fair balance of mechanical behaviour. This seems to be a consequence of complex influencing the multiphase system by clay such as modification of components (reinforcement) and parameters of the interface accompanied by influencing the dynamic phase behaviour, i.e., the compactibilizing effect. The paper analyses the effect of nanocomposites and type of the material on the individual measured parameters, relations between them, strength and deformation behaviour. Deformation was evaluated by non-contact videoextensometry metho