Laser Cladding Of Powder Research Articles

Tribological properties and microstructures of Al2O3-TiC-TiB2 reinforced composites

Abstract Ti-3Al-2V alloy is an important aviation material but shows poor resistance to slid wear. Laser cladding of the Fe3Al-B4C pre-placed powders on a Ti-3Al-2V substrate can form the TiC-TiB2 reinforced composites, which improved the wear resistance of the substrate. In this study, it was noted that the addition of the Al2O3 and 7 wt.% yttria partially stabilized zirconia (YPSZ) was able to further increase the wear resistance of such composites. Al2O3 increased the dilution rate of the substrate to the laser molten pool to a certain extent; moreover, Al2O3 improved the hardness, elastic modulus and the mechanical properties of such laser clad composites. The YPSZ addition led t-ZrO2-ZrSiO4 to be produced in such composites.

Surface modification of AISI H13 tool steel by laser cladding with NiTi powder

This paper presents laser cladding of NiTi powder on AISI H13 tool steel surface for surface properties enhancement. The cladding process was conducted using Rofin DC-015 diffusion-cooled CO2 laser system with wavelength of 10.6 µm. NiTi powder was pre-placed on H13 tool steel surface. The laser beam was focused with a spot size of 90 µm on the sample surface. Laser parameters were set to 1515 and 1138 W peak power, 18 and 24 % duty cycle and 2300–3500 Hz laser pulse repetition frequency. Hardness properties of the modified layer were characterized by Wilson Hardness tester. Metallographic study and chemical composition were conducted using field emission scanning electron microscope and energy-dispersive X-ray spectrometer (EDXS) analysis. Results showed that hardness of NiTi clad layer increased three times that of the substrate material. The EDXS analysis detected NiTi phase presence in the modified layer up to 9.8 wt%. The metallographic study shows high metallurgical bonding between substrate and modified layer. These findings are significant to both increased hardness and erosion resistance of high-wear-resistant components and elongating their lifetime.

Microstructural evolution and bonding characteristic in multi-layer laser cladding of NiCoCr alloy on compacted graphite cast iron

Laser cladding of NiCoCr alloy powder on cast iron was performed with a 1kW Nd:YAG continuous laser. Despite numerous advantages, one of the most critical issues is the formation of martensite and a brittle layer in the vicinity of the bonding interface due to the inherent rapid cooling, which might result in cracking nearby and a decrease in bonding strength. The objective of this research is to produce well bonded NiCrCo alloy coating that is free of pores and cracks on cast iron without preheating the whole substrate. Considering the poor weldability of cast iron, the strategy of reciprocated deposition, namely multi-layer laser cladding, was applied. The microstructural evolution of the multi-layer coating on the cast iron was investigated with the emphasis on the variation of the bonding zone. The results showed that NiCoCr coatings with different layers consisted of fine solid solution dendrites surrounded by an inter-dendritic network of precipitates. The multi-layer clad coating had a gradual distribution of elements, which was different from that in the single layer coating. The martensite near the bonding interface was transformed into tempered sorbite under the thermal influence of multi-layer deposition, leading to a decrease in the high micro-hardness zone width. A bending test confirmed that the bonding brittleness was reduced and the mechanical properties were improved through the use of the multi-layer laser cladding approach.

Finite Element Analysis of the Temperature Field in Laser Cladding of Ni-Based Powders on Teeth Surfaces of the Helical Gear

Finite Element Analysis of the Temperature Field in Laser Cladding of Ni-Based Powders on Teeth Surfaces of the Helical Gear

Eddy-current testing of fatigue degradation under contact loading of NiCrBSi coatings obtained through gas–powder laser cladding

The possibilities of using the eddy-current method for testing the fatigue degradation under contact loading of NiCrBSi coatings were investigated. These coatings are obtained using the method of the gas–powder laser cladding from powders with different contents of chromium, boron, carbon, and additives of titanium carbide TiC (15 and 25 wt. %). It was established that eddy-current testing of fatigue degradation under contact loading of PG-SR2 and PG-10N-01 coatings can be performed at high excitation frequencies of an eddy-current transducer, when the depth of the analyzed layer is maximally close to the thickness of the surface layer that was subjected to fatigue degradation. Testing the fatigue degradation under contact loading of TiC–PG-SR2 composite coatings with TiC-additive contents of 15 and 25 wt. % has certain limitations and features that result from the presence of a significant number of discontinuity flaws in the structure of these coatings.

Laser Cladding of γ-TiAl Intermetallic Alloy on Titanium Alloy Substrates

The enhancement of titanium and titanium alloy's tribological properties is of major interest in many applications such as the aerospace and automotive industry. Therefore, the current research paper investigates the laser cladding of Ti48Al2Cr2Nb powder onto Ti6242 titanium alloy substrates. The work was carried out in two steps. First, the optimal deposition parameters were defined using the so-called “combined parameters,” i.e., the specific energy E specific and powder density G. Thus, the results show that those combined parameters have a significant influence on the geometry, microstructure, and microhardness of titanium aluminide-formed tracks. Then, the formation of dense, homogeneous, and defect-free coatings based on optimal parameters has been investigated. Optical and scanning electron microscopy techniques as well as energy-dispersive spectroscopy and X-ray diffraction analyses have shown that a duplex structure consisting of γ-TiAl and α 2-Ti3Al phases was obtained in the coatings during laser cladding. Moreover, it was shown that produced coatings exhibit higher values of microhardness (477 ± 9 Hv0.3) and wear resistance (average friction coefficient is 0.31 and volume of worn material is 5 mm3 after 400 m) compared to those obtained with bare titanium alloy substrates (353 Hv0.3, average friction coefficient is 0.57 and a volume of worn material after 400 m is 35 mm3).

Investigation of the Laser-Powder Cladding Effect on Steel Surface Hardening

The investigation was carried out in the laser-technological complex with the power up to 8 kW, ITAM SB RAS. An inert-gas jet was supplied coaxially with the beam. A protective nozzle from which gaseous Ar was injected was used to protect the hardening joint. The parameters of the laser hardening process with the surface alloying was optimized on the samples of low-carbon steel 20, construction steel 45, and spring steel 65G.Special cladding powders containing carbon, manganese, nickel, chromium, molybdenum, tungsten, silicon, boron, and nitrogen were chosen for laser-powder cladding. They are intended for cladding wear-resistant layers onto machine parts, tools and equipment operated under abrasion-wear conditions with moderate shock loading.It was found that an optimal radiation power was 2 kW. Extra water cooling of treated parts is unpractical during laser hardening because it did not improve the hardening effect. The best effect of surface alloying was reached when the powder of rapid tool steel Р6М5 was injected in the liquid metal pool. High hardness of the clad layer remained at further heating up to 550°C. The use of laser thermal treatment and laser-powder cladding provides thermal hardening and enables increasing hardness and hence wear resistance of low-carbon steel parts by 3 - 4 times, whereas the base part remains viscous.

System for laser microsurfacing of metal powders

The article presents the technology of laser cladding of metallic powders and a machine for laser microsurfacing developed for this purpose. This specifically designed and manufactured station is based on a three-axis CNC machine, equipped with appropriate laser safety systems and a dust extraction system. A disc laser is used as a source of laser energy, connected with the processing optics by a fibre optic cable. A brush powder feeder with a nozzle for shaping the flow of powder transfers the powder coaxially with the laser beam. The system is integrated with a PC-motion card which acts as a CNC controller. The article also presents the results of laser surfacing experiments, classified in terms of the following criteria: surfacing height, width and depth of penetration, wetting angle and microstructural parameters. The laser power density, powder feeding rate and density, as well as the relative movement of the welding head against the component, have been selected as independent parameters.

Influence of additions of nanoparticles TaC on a microstructure laser cladding

The features of a laser cladding of nickel-based powders with TaC nanopowder additives have been experimentally investigated. The minimum depth of pro-melting of a basis, microhardness distribution over the cross section of the substrate, and the saturation of the metal of the cladding with basis components has been determined in the experiments.

The Tool Laser Beam with New Degrees of Freedom

AbstractHighly dynamic drives, e. g., piezo or voice coil drives, enable a high‐frequency deflection of the laser beam on the workpiece surface. Modern solid‐state lasers allow modulation of the specified laser power in frequencies of several kilohertz. If these possibilities are combined strictly synchronously, the result is previously unavailable technological advantage on the component to be processed: the programmable beam quality. Using the example of specific optical and machine solutions, the following describes how these possibilities have been realised for industrial use and proves the technological advantages on application examples in the processes of laser welding and laser powder cladding.

Synthesis of an auxiliary electrode by laser cladding coating for in-situ electrochemical sulfur sensing

Compact auxiliary electrode layer (MgS+MgO–PSZ) was fabricated on the MgO partially stabilized zirconia (MgO–PSZ) substrates by laser powder cladding (LPC) technique. The microstructure, composition and electrochemical performance of the MgS+MgO–PSZ layer were investigated using X-ray diffraction, scanning electron microscope and electrochemical impedance spectroscopy. The result indicated that the structure of the coating was dense and uniform. Furthermore, the auxiliary electrode was found to be efficient for zirconia-based sensor by forming numerous MgS/MgO–PSZ interface that make the S/O equilibrium established effectively.

Effects of Laser Cladding Process on Cladding Layer Qualities of Nickel-Base Alloy

Nickel-base alloy powder is widely applied to strengthen the surface of products through laser processing. This paper presents the experiments on laser cladding of Ni45 alloy powder on substrates of 45 steel. The experimental results show that the laser cladding processing parameters such as laser power, scanning speed, powder feed rate and overlap ratio have great effects on the qualities of the cladding layer. Optimizing the processing parameters is an effective way to improve the layer qualities and obtain desired cladding layers.

Effect of laser parameters on microstructure and hardness of laser clad and tempered AISI H13 tool steel

In the present study, laser cladding of AISI H13 tool steel powder has been undertaken on hardened and tempered AISI H13 tool steel components using a 6kW fiber coupled diode laser both in continuous wave and pulsed mode with coaxial powder feeder to explore the possibility of reclamation/refurbishment of large AISI H13 tool steel components. Laser parameters in terms of laser power, processing speed and powder feed rate have been optimized to achieve acceptable clad-substrate integrity with optimum deposition height and width without any surface cracks and porosity. A detailed study of the effect of post-cladding heat treatment (both by laser assisted surface heating and conventional tempering at 550°C) on the microstructure, phase aggregate, crystallite size, micro-strain and residual stress was carried out. Subsequently, the microhardness of the clad zone was evaluated. Pulsed laser cladding (heat input controlled) with 50Hz frequency and 50% duty cycle with 10ms ON-time developed a microstructure comprising martensite, retained austenite and mixed carbides. The maximum improvement in hardness (considered as a convenient index of strengthening) by laser cladding reached up to 650VHN, which is about 45% higher than the hardness of hardened and tempered substrates. Post-cladding tempering at 550°C for 2h led to the development of uniform microstructure without fine carbide precipitated along grain boundaries or inter-dendritic regions taking the hardness to 600–650VHN level. Laser reheating (tempering) of the clad zone with a 1000W laser power showed a more refined microstructure with maximum hardness up to 680–700VHN. Residual stress, developed on the surface after laser cladding, was compressive in nature and measured higher in magnitude after pulsed laser cladding. Magnitude of this residual compressive stress marginally decreased after post-cladding tempering either by conventional or laser assisted route. Thus, the novelty of the present study lies in the continuous or pulsed mode laser cladding assisted reclamation of AISI H13 hot working dies with similar composition powder, followed up with conventional or laser assisted tempering, leading to the development of about 45% higher hardness (than as hardened and tempered conditions) and retention of residual compressive stress on the surface after cladding.

Effect of defocus manner on laser cladding of Fe-based alloy powder

This investigation was focused on the influences of defocus manner and composite powders on laser cladding. Combining with the transmission characteristic of parallel Gaussian laser beam through a focusing lens, the energy distribution of the cross section of the laser beam in positive and negative defocused zone was analyzed and also verified by laser dotting ablation. Comparing with positive defocus, the negative defocus is an effective way for high quality laser cladding providing more advantages. Therefore, the negative defocus method is selected to solve the problem of high dilution rate and pores in the overlapping coating. The study showed that by adjusting the process parameters, a coating with low dilution and free of pores can be achieved easily in the negative defocus. Finally, the microstructure and microhardness of Fe-based alloy mixed with 5wt.% Cr3C2 coating were analyzed.

Study on Macroscopic Morphology and Microstructure of Single Ni60 Laser Clad Tracks Prepared Using a Variable Laser Beam Shaper

The objective of the present study was to find the influence of laser beam shape on macroscopic morphology and microstructure of single Ni60 laser clad tracks. Laser cladding of Ni60 alloy powder can be used to manufacture and remanufacture backup rollers for the steel industry. Controlling temperature distribution can assist with achieving favorable macroscopic morphology and microstructure. Five different beam profiles were used in our experiment to prepare clad tracks. The beam profiles varied in terms of the ratio of energy densities between the internal and external parts. The macroscopic morphology and microstructure was tested using SEM. The study founds decreasing the ratio is possible to achieve wider clad tracks with a larger cross section area. It was found that microstructure in upper region tended to form net-like dendrite microstructure at low energy density ratios.

Modeling and Numerical Study of Light-propulsion Phenomena of Particles Acceleration in Coaxial Laser Powder Cladding

This work presents the results of investigation of heating and laser acceleration of powder particles in the laser cladding conditions. The model of reactive particles motion developed by the authors made a base for the numerical analysis of the laser particles acceleration. At the laser cladding, the light-propulsion force may be quite high, and powder particles may be acc elerated up to several tens of meters per second and more. Numerical studies were carried out for two types of coaxial laserpowder nozzles. Powder feeding ways (symmetrical and asymm etrical), particles size and flow rate were varied. CO2-laser radiation had the wavelength of 10.6Pm, power up to 4.5 kW. Stainless-steel and aluminum-oxide powders were studied. Comparability of the model calculation and experimental data is discussed.

镍硅硼合金粉末激光熔覆中熔池光谱检测分析

镍硅硼合金粉末激光熔覆中熔池光谱检测分析

Concurrent Inconel 625 wire and WC powder laser cladding: process stability and microstructural characterisation

The microstructure and hardness property of WC powder–Inconel 625 wire single tracks deposited by laser cladding at varying processing parameters were investigated using a combination of scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffraction, image processing software and hardness testing. The results include the generation of process maps that predict the cladding process characteristics at varying processing conditions. High dissolution of WC particles at high energy input resulted in a decrease in retained WC volume fraction with increasing laser power. The negative dependence of the retained WC volume fraction on the transverse speed and wire feedrate showed that the decreasing powder catchment efficiency with increasing the two parameters is primarily significant to the amount of WC contained in a track. The dissolution of WC in the matrix resulted in the formation of W2C and Fe3W3C hard phases, which mainly contributed to high hardness (540–690 HV0·3) of the composite matrix.

분말송급 및 와이어송급을 이용한 레이저 클래딩 특성

In this research, laser cladding characteristics were investigated for various filler metal feeding methods such as powder, cold wire, and hot wire feeding. Appropriate parameter window, deposition rate, material efficiency and dilution for each filler feeding method were evaluated with same laser power and cladding speed range. Laser powder cladding has wider process parameter window but higher material efficiency and lower dilution were achieved by laser wire cladding. Among these feeding methods, laser hot-wire cladding showed best efficiency in material usage and deposition rate.

Investigation into Heat Treatment and Residual Stress in Laser Clad AA7075 Powder on AA7075 Substrate

The laser cladding of AA7075 powder onto a AA7075 substrate was conducted to evaluate the effect of heat treatment and to measure residual stress between the clad layer and substrate to better understand the effect of laser cladding. The microstructure formed in the clad region was characteristic of a high cooling rate, which is typical for laser cladding. The heat-affected zone (HAZ) showed coarser precipitates when compared with the substrate and was attributed to the heating from the laser. A solution heat treatment followed by aging was employed to restore the strength in the HAZ. Nanohardness traverses of the clad and substrate was performed and it was shown the hardness in the 7075 clad layer was lower than the substrate both pre- and post-heat treatment and was attributed to the vaporization of zinc and magnesium. Neutron diffraction was employed to measure the residual stress both before and after heat treatment. The residual stresses formed in the clad layer were tensile and about 50 MPa in magnitude; heat treatment increased the stress level to approximately 100 MPa.