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A. Lisiecki

Abstract

The autogenous laser welding of 2.5 mm thick butt joints of thermomechanically rolled fine-grain steel grade S420MC was investigated. Butt joints were laser welded by the Yb:YAG Disk laser, emitted a circular laser beam with spot diameter of 200 μm at 1.03 μm wavelength, and also by the high power direct diode laser, emitted a rectangular beam with dimension of 1.8x6.8 mm at 808 nm wavelength. Different welding modes were identified for the lasers applied. The conduction welding mode was observed in whole of the diode laser welding parameters. While high quality joints, without any internal defects and characterized with satisfactory mechanical performance were produced in a wide range of parameters. The butt joints produced by Disk laser were welded at keyhole mode. In this case a slight tendency to weld porosity was found.

Open access

A. Lisiecki

The paper presents a detailed analysis of the influence of heat input during laser bead-on-plate welding of 5.0 mm thick plates of S700MC steel by modern Disk laser on the mechanism of steel penetration, shape and depth of penetration, and also on tendency to weld porosity formation. Based on the investigations performed in a wide range of laser welding parameters the relationship between laser power and welding speed, thus heat input, required for full penetration was determined. Additionally the relationship between the laser welding parameters and weld quality was determined.

Open access

A. Lisiecki

Abstract

The article presents the results of a comparative study of the nitriding process of titanium alloy substrate using two lasers with different characteristics of laser beams. One of the applied lasers was a high power diode laser emitting at a dominant wavelength of 808 nm, with a rectangular laser beam spot, and multimode energy distribution across the spot. The second laser was a solid state Yb:YAG disk laser emitting at a wavelength of 1.03 μm, with a circular beam spot, characterized by near Gaussian energy distribution across the spot. In a case of both lasers single stringer beads with a similar width and at similar energy input were produced. As a result of melting of the substrate with a laser beam in a pure gaseous nitrogen atmosphere composite surface layers with in situ precipitated titanium nitrides embedded in the metallic matrix of titanium alloy were produced, in both cases. However, the surface topography and structure is different for the surface layers produce by different lasers at the same processing parameters and width of laser beams.

Open access

A. Lisiecki

Autogenous laser welding of 5.0 mm thick butt joints of thermomechanically rolled steel S700MC was investigated. The Yb:YAG disk laser TruDisk 3302 emitted at 1.03 μm was used for the trials of autogenous welding. The effect of laser welding parameters and thus thermal conditions of welding on weld shape, microstructure of weld metal and heat affected zone (HAZ), tensile strength, bending angle, impact toughness and microhardness profile was determined. Studies have shown that it is advantageous to provide a high welding speed and low heat input. High cooling rate of weld metal and HAZ leads to the formation of a favorable structure characterized by a large proportion of fine-grained acicular ferrite and provides high mechanical properties of butt joints.

Open access

A. Lisiecki and J. Piwnik

Abstract

In order to improve the tribological properties of titanium alloy Ti6Al4V composite surface layers Ti/TiN were produced during laser surface gas nitriding by means of a novel high power direct diode laser with unique characteristics of the laser beam and a rectangular beam spot. Microstructure, surface topography and microhardness distribution across the surface layers were analyzed. Ball-on-disk tests were performed to evaluate and compare the wear and friction characteristics of surface layers nitrided at different process parameters, base metal of titanium alloy Ti6Al4V and also the commercially pure titanium. Results showed that under dry sliding condition the commercially pure titanium samples have the highest coefficient of friction about 0.45, compared to 0.36 of titanium alloy Ti6Al4V and 0.1-0.13 in a case of the laser gas nitrided surface layers. The volume loss of Ti6Al4V samples under such conditions is twice lower than in a case of pure titanium. On the other hand the composite surface layer characterized by the highest wear resistance showed almost 21 times lower volume loss during the ball-on-disk test, compared to Ti6Al4V samples.

Open access

R. Burdzik, T. Wegrzyn, Ł. Konieczny and A. Lisiecki

Abstract

The paper presents results of research on influence of fatigue metal damage of the inner race of bearing on vibration in different frequencies. The active diagnostics experiments were conducted on application of vibroacoustics methods for technical condition monitoring. Provides an overview of materials and process analysis of rolling bearings wear. The bearing damage of the inner race have been simulating. The research was conducted on special research-educational test bench for vibration monitoring for rotaring machinery. For the identification of the symptoms of the defects in the vibration signal the analysis of time realization and frequency transformation of the vibration have been conducted. For the comparison of the vibration of good and damage bearings signals registered for different frequencies have been presented in form of spectrograms and RMS distributions.

Open access

P. Skubisz, A. Żak, M. Burdek, Ł. Lisiecki and P. Micek

Abstract

Effect of plastic processing and controlled cooling on microstructure and mechanical properties of experimental steel grades with microalloyed with Ti, V and/or Nb, varying in the content of Mo is presented as an offer for mining industry for replacement traditionally heat-treatable hardenability grades. The goal of the work is producing microstructure condition, which after controlled hot forging and direct heat treatment, involving quenching and self-tempering, are meant to provide good combination of mechanical properties, such as TYS 800 MPa, UTS 1050 MPa, elongation to fracture at least A5 15% and/or impact strength at room temperature KCV 60 J/cm2. Hardenability assessment and dilatometric examination allowed formulation of direct heat treatment guidelines, taking into consideration fields of temperature and strain in a typical hot forging process, estimated numerically, with the use of plastometric tests results, as well as the use of unique cooling cycles after forging.

On the basis of numerical analysis of thermomechanical parameters and temperature progression, hot forging and direct cooling conditions were selected to achieve assumed structural components, morphology and dispersion of both grain and precipitates. For established heat transfer model and experimentally plotted cooling curves numerical analysis of direct cooling, enabled by definition of characteristic points of austenite transformation and CCT diagrams was conducted. The modeling aided with dilatometric characterization enabled prediction of transformation products distribution. The formulated conclusions were verified in the experimental sampling of forging, evaluating the applicability of designed combinations of chemical composition and cooling cycle for selected forged part for mining industry.

Open access

A. Lisiecki, R. Burdzik, G. Siwiec, Ł. Konieczny, J. Warczek, P. Folęga and B. Oleksiak

Autogenous laser welding of 0.8 mm thick butt joints of car body electro-galvanized steel sheet DC04 was investigated. The Yb:YAG disk laser TruDisk 3302 with the beam spot diameter of 200 μm was used. The effect of laser welding parameters and technological conditions on weld shape, penetration depth, process stability, microstructure and mechanical performance was determined. It was found that the laser beam spot focused on the top surface of a butt joint tends to pass through the gap, especially in the low range of heat input and high welding speed. All test welds were welded at a keyhole mode, and the weld metal was free of porosity. Thus, the keyhole laser welding of zinc coated steel sheets in butt configuration provides excellent conditions to escape for zinc vapours, with no risk of porosity. Microstructure, microhardness and mechanical performance of the butt joints depend on laser welding conditions thus cooling rate and cooling times. The shortest cooling time t8/5 was calculated for 0.29 s.

Open access

A. Kurc-Lisiecka, J. Piwnik and A. Lisiecki

Abstract

The article presents results of investigations on autogenous laser welding of new grade STRENX 1100 MC steel. The modern Disk laser was applied for of 5.0 mm thick butt joints welding. The influence of laser welding parameters, mainly the energy input of laser welding on the penetration shape, weld quality, structure and mechanical performance was investigated. It was found that the investigated steel has surprisingly low carbon equivalent CET just 0.328, and also relatively high temperature of martensitic transformation Ms at 430.6°C. Despite very rapid cooling times t8/5 in a range from 0.6 to 1.3 s, thus rapid solidification there was no tendency to cracking of weld metal or HAZ. Significant drop of microhardness in the HAZ resulted in a decrease of tensile strength of joints, compared to the base metal. Impact toughness of test joints was at only 50÷60% of the base metal.

Open access

R. Burdzik, Ł. Konieczny, Z. Stanik, P. Folęga, A. Smalcerz and A. Lisiecki

Abstract

The paper provides an analysis of the reasons for excessive wear of the camshafts system components based on models developed to describe the impact of selected material, technological and operational factors. The subject of the research was wear of camshaft cams studied in accordance with results of operation tests. Based on the said tests, the dependence of wear intensity of cams from their angular position was established. The respective calculation results enabled the function of cam fallibility to be determined.