Improving rail wear and RCF performance using laser cladding

Wear, In Press, Corrected Proof, Available online 17 May 2016

S.R. Lewis, S. Fretwell-Smith, P.S. Goodwin, L. Smith, R. Lewis, M. Aslam, D.I. Fletcher, K. Murray, R. Lambert

Abstract:Laser cladding has been considered as a method for improving the wear and RCF performance of standard grade rail. This paper presents results of small scale tests carried out to assess the wear and RCF performance of rail which had been laser clad. Using the laser cladding process premium metals can be deposited on to the working surface of standard rail with the aim of enhancing the wear and RCF life of the rail. Various laser clad samples were tested using a twin-disc method. The candidate metals were clad on to standard R260 grade rail discs and were tested against a disc of standard wheel material. During the tests, wear rates and RCF initiation were monitored and compared to those of a standard rail disc. Six candidate cladding materials were chosen for this test: A multi-phase Manganese Steel Variant (MMV), Martensitic Stainless Steel (MSS), TWIP Steel, NiCrBSi, Stellite 12 and Stellite 6. The MSS, Stellite 6, and Stellite 12 samples showed reduced wear rates relative to the standard R260 Grade rail discs, and also produced a reduction in wheel steel wear. The RCF initiation resistance of all of the candidate materials was superior compared to the R260 Grade material.

Analysis and optimization of process parameters in Al–SiCp laser cladding

Optics and Lasers in Engineering, Volume 78, March 2016, Pages 165-173

Ainhoa Riquelme, Pilar Rodrigo, María Dolores Escalera-Rodríguez, Joaquín Rams

Abstract:The laser cladding process parameters have great effect on the clad geometry and on dilution in the single and multi-pass aluminum matrix composite reinforced with SiC particles (Al/SiCp) coatings on ZE41 magnesium alloys deposited using a high-power diode laser (HPLD). The influence of the laser power (500–700 W), scan speed (3–17 mm/s) and laser beam focal position (focus, positive and negative defocus) on the shape factor, cladding-bead geometry, cladding-bead microstructure (including the presence of pores and cracks), and hardness has been evaluated. The correlation of these process parameters and their influence on the properties and ultimately, on the feasibility of the cladding process, is demonstrated. The importance of focal position is demonstrated. The different energy distribution of the laser beam cross section in focus plane or in positive and negative defocus plane affect on the cladding-bead properties.

Annular Laser Beam Cladding Process Feasibility Study

Physics Procedia, Volume 83, 2016, Pages 647-656

Alexander Kuznetsov, Andrej Jeromen, Gideon Levy, Makoto Fujishima, Edvard Govekar

Abstract:In the paper a novel annular – ring shaped – laser beam cladding head and related cladding process are presented. In the cladding head a laser beam is shaped into an annular ring and guided coaxially with the powder tube disposing the powder jet in the centre of the focused annular laser beam ring. An experimental process feasibility analysis was performed using a Nd:YAG pulsed laser system with a maximal average power 250 W. Beside the known influencing parameters of laser cladding process including the powder mass flow, workpiece feeding velocity, and laser beam intensity, the important parameters related to the annular laser beam caustics were defined. The process feasibility and influence of the process parameters on powder catchment efficiency was analysed based on the cladding experiments of SS 316L powder on SS 304 workpiece material. The potential benefits related to the annular laser beam melt pool geometry and related powder catchment efficiency are discussed.

Effect of Laser Cladding Parameters on the Microstructure and Properties of High Chromium Hardfacing Alloys

Physics Procedia, Volume 83, 2016, Pages 684-696

E. Abouda, M. Dal, P. Aubry, T.N. Tarfa, I. Demirci, C. Gorny, T. Malot

Abstract:Mechanical components operating under high-stress and high-temperature environments require enhanced mechanical and tribological properties. In this research, different high chromium steels (Fe-Cr-C-Ni-Mo-Mn) have been coated over a 316L substrate using coaxial laser cladding. Optimized properties of the clad (such as adhesion, compactness, microstructure and dilution rate) have been obtained by a broad parameter search (laser power, powder feeding rate, scanning speed and preheating). Varying such parameters induces change in the microstructure, chemical distribution, morphology and properties of deposits. These have been thoroughly characterized in terms of metallurgical structure, phase compositions and functional properties using dedicated metallurgical mechanical and wear analysis. Samples obtained by laser cladding and plasma arc-transferred cladding have been compared. Laser cladding exhibits a significant strengthening mechanism for this hardfacing alloy. This results from a finer dendritic structure with a modified Chromium and Molybdenum precipitations distribution in the eutectic interdendritic phase.

Possibility of Multi-material Laser Cladding Fabrication of Nickel Alloy and Stainless Steel

Physics Procedia, Volume 83, 2016, Pages 634-646

D. Kotoban, A. Aramov, T. Tarasova

Abstract:There are some applications in the industry for multi-material components, including device engineering and multifunctional surface engineering, having to eliminate a brazing or welding technological step. This study investigates the laser cladding process parameters, related single track geometry and quality of multi-material samples. The optimal process parameters for steel were found of 0.21-0.26 J/mm2 and 0.25 10-2 g/mm under the scanning velocity of 1400-1700 mm/min and powder feeding of 4.2-4.5 g/min. The bimetal thin walls, cylinders and cubes were manufactured within the optimal conditions. The requirements of steel and nickel joining were explored. For the examination, the optical microscopy, SEM, EDX microelement analysis and hardness analysis were involved.

Laser cladding as repair technology for Ti–6Al–4V alloy: Influence of building strategy on microstructure and hardness

Materials & Design, Volume 85, 15 November 2015, Pages 497-510

H. Paydas, A. Mertens, R. Carrus, J. Lecomte-Beckers, J. Tchoufang Tchuindjang

Abstract:Laser cladding is a metal deposition technique used to fabricate or repair components made from high value metallic alloys. In the present work Ti–6Al–4V deposits with variable thickness are made to assess the use of laser cladding as a repair technology. Both the effect of the building strategy (BS) and the incident energy (IE) on the metallurgical characteristics of the deposits in relation to their complex thermal history have been studying. It is shown that for the configuration consisting in a decreasing track length (DTL) under high IE, a gradient of cooling rate exists that leads to the presence of different phases within the microstructure. Conversely homogeneous microstructures are present either for the configuration with a constant track length (CTL) under high IE, and for the strategy obtained from a DTL under low IE. Depending on the possible heat accumulation the nature of the phases are determined together with hardness maps within the deposits. Some qualification criteria are set prior to tensile tests to selected adequate candidate-deposit that does not weaken the cladded material when it is stressed. A thermo-metallurgical scheme is proposed that helps in understanding the effect of both the BS and the IE on the microstructure.