Evaluation of Mechanical Properties and Microstructure for Laser Deposition Process and Welding Process (original) (raw)
Related papers
H13 tool steel with excellent hot working properties is commonly used for manufacturing dies. However, the damage of die surface due to cyclic thermo-mechanical loading is detrimental to the service life. In order to enhance the die life, it has been observed that cladding based repair is superior to welding or thermal spraying repair techniques. In this paper, experimental study of laser cladding of H13 has been carried out. CPM 9V steel powder has been deposited on H13 tool steel plate for repairing the die surface damage using a CW CO 2 laser in conjunction with powder injection system. The effect of laser parameters on clad geometry and clad quality has been investigated. The microstructure of laser cladded samples has been characterized using optical microscope (OM) and scanning electron microscope (SEM). The phases and the residual stresses present in the clad have been determined via X-ray diffraction. The micro-hardness profiles obtained in the clad–substrate system and the hardness change due to cyclic thermal loading have also been characterized. Optical micrographs of the clad microstructure shows existence of vanadium carbide particles embedded in martensite and retained austenite. The hard vanadium carbide particles increase the clad hardness to an average of four times greater than the substrate hardness. It has been observed that compressive residual stresses are generated in clad which is desirable for repair applications as it will impede the crack propagation resulting in enhanced die life.
Mould steels repaired by laser welding
Laser-deposit welding, by using Nd-YAG, is a mould repairing process, which has the advantages relatively to the traditional methods of achieving a less change of the metal composition around the repaired zone and permitting a very accurate deposition of a small volume of the filler material in the area chosen at the work-piece surface. This paper presents a fatigue study in specimens of two base materials used in mould production (AISI H13 and P20). Filler material as well as welding parameters were analysed in order to obtain better fatigue strength. The tests were carried out under constant amplitude loading, with two stress ratios R = 0 and R = 0.4. Welded specimens were prepared with V notches and filled with laser welding deposits. The fatigue results are presented in the form of S-N curves obtained in welded and non-welded conditions. Complementary measurements of hardness profiles and SEM analysis were carried out to understanding the fatigue behaviour and failure sites. The laser-deposit material was the weaker region in both steels, due to a high level of tensile residual stresses and also to some planar defects that are potential failure sites. Fatigue crack initiation is therefore reduced and the fatigue propagation life is enhanced. A significant mean stress effect in the base material was also observed in both mould steels.
Microstructure and mechanical properties of laser cladding repair of AISI 4340 steel
2012
Laser cladding (LC) was used to investigate the repair of high strength steel in aircraft applications, such as landing gears. This paper reports on the microstructure and microhardness properties of the deposited AISI 4340 clad layer on AISI 4340 steel substrate. Microhardness results showed the clad layer was 30-40% harder than the base material. Stress relieving the clad allowed the clad and HAZ areas to soften 10% below the base material. High dilution provided a favorable result on the hardness at the interface.
Microstructural evolution of tool steels after Nd-YAG laser repair welding
Journal of Materials Science, 2004
The present paper is aimed at investigating the microstructural behaviour of tool steels after repair welding or refurbishing by a pulsed Nd-YAG precision laser. The 1.2311 (40CrMnMo7), 1.2083 (X42Cr13) and 1.2343 (X38CrMoV5-1) steels were selected for experimental investigations to cover a wide range of steel grades, commonly used in tooling industry. Laser repair welding condition was simulated by preparing small deposits in one or more passes on steel samples having several reference geometries. Investigations on microstructural properties, microhardness evolution and on defect formation were carried out. The effects of different laser welding parameters were also considered. The study allowed to state several fundamental information on tool behaviour during repair welding in order to gain a deeper insight into this process, routinely considered in industrial practice but often neglected in scientific research works on welding metallurgy.
Remanufacturing H13 steel moulds and dies using laser metal deposition
2016
The exploitation of Additive Manufacturing (AM) in the repair and remanufacture of industrial components, such as moulds and dies, has become an emerging research area due to the expected reduction of replacement cost and the promise of better mechanical and wear resistance properties – moreover, the use of remanufacturing standards ensures a greater than or equal to warranty part quality. Further studies plan to utilize Laser Metal Deposition (LMD) to remanufacture artificially worn H13 Steel samples, allowing benchmarking studies to be conducted in order to compare the mechanical and wear resistance performance of LMD against current welding repair technologies. The specimens will be subjected to an accelerated pressure and elevated temperatures schedule, simulating the loading cycles during the use of the die sets. The effects on the resulting part properties of different process parameters setup, including the type and characteristics of the deposited powder will be studied.
Effects of advanced laser processing on the microstructure and residual stresses of H13 tool steel
2017
The aim of this paper is to describe the effects of laser processing on the microstructure and residual stresses of laser cladded H13 tool steel on the classical construct steel S355 substrate. This research paper concludes that in this case of laser cladding, phase transformation and not shrinkage is likely to be a dominant effect on the formation of compressive residual stresses along the clad. Furthermore, martensitic structure and unequal concentration of alloying elements was observed on the cross-section of the clad using electron backscattering diffraction and energy-dispersive X-ray spectroscopy.
Laser cladding (LC) was used to investigate the repair of high strength steel in aircraft applications, such as landing gears. This paper reports on the microstructure and microhardness properties of the deposited AISI 4340 clad layer on AISI 4340 steel substrate. Microhardness results showed the clad layer was 30-40% harder than the base material. Stress relieving the clad allowed the clad and HAZ areas to soften 10% below the base material. High dilution provided a favorable result on the hardness at the interface.
Surface Repair of Tool Made of 12 Ni Maraging Steel by Laser Cladding of NiCoMo Powder
Advanced Materials Research, 2010
Surface repair experiments with Nd:YAG coaxial laser cladding of NiCoMo maraging powder were made on specimens from maraging steel (EN 10027-2, mat. no. 1.2799). The influences of different modes of laser-beam guidance with various powder mass flows and with different degrees of overlapping of individual traces on the dilution and the repair area were determined. The micro and macroscopic analyses of microsections of fusion zone (FZ), heat affected zone (HAZ) and through-depth microhardness were analysed after cladding and after subsequent solution and precipitation annealing. The microchemical (EDS) analysis was performed at various depths. The residual stresses in the clad face and in the clad toe were determined and compared, using the hole-drilling method.
A Problems in Laser Repair Welding of Polished Surfaces
Metalurgija -Sisak then Zagreb-
This paper presents problems in laser repair welding of the tools for injection moulding of plastics and light metals. Tools for injection moulding of the car headlamps are highly polished in order to get a desirable quality of the in-jected part. Different light metals, glasses, elastomers, thermoplastics and thermosetting polymers are injected into the die cavity under high pressures resulting in the surface damages of the tool. Laser welding is the only suitable repair welding technique due to the very limited sputtering during deposition of the filler metal. Overlapping of the welds results in inhomogeneous hardness of the remanufactured surface. Results have shown strong correlation between hardness and surface waviness after final polishing of the repair welded surface.