Re-melted Zone Research Articles

Microstructure and Properties of the Copper Alloyed with Ag and Ti Powders Using Fiber Laser.

The scope of the work covers the development of the relationship between the chemical composition of surface-modified copper and the diffusion of alloy elements as well as the microstructure and mechanical properties. This article presents the impact of laser alloying with titanium and silver powders on the microstructure and mechanical properties of copper. In order to investigate the phenomena occurring during the laser alloying process, microstructural studies were performed using scanning electron microscopy (SEM), optical microscopy, and energy dispersive x-ray spectroscopic (EDS) analysis of the chemical composition in micro-areas. In addition, to test the properties of the resulting alloy, abrasion resistance, hardness measurement at low loading force, and conductivity measurements were performed. As a result of alloying with Ag and Ti powders, three distinct zones were indeed recognized: re-melting zone (RZ), diffusion zone (DZ), and heat affected zone (HAZ). The surface modification that results from laser alloying increases the hardness as well as the abrasion resistance of the material. Overall, it was found that laser alloying with Ti powder increased the strength of the copper surface layer due to the formation of intermetallic phases (Cu3Ti2). It was also found that laser alloying with Ag powder changed the mechanical properties of the surface layer due to the solid solution strengthening.

The effect of temperature distribution and cooling rate on microstructure and microhardness of laser re-melted and laser-borided carbon steels with various carbon concentrations

Laser heat treatment was arranged as a laser remelting and laser boriding. Materials with different carbon concentration were used. Three zones characterized the microstructure after laser treatment: re-melted zone (MZ), heat-affected zone (HAZ) and substrate material. The differences in carbon content and physical properties of used materials influenced the obtained microstructure, temperature distribution and hardness. In case of laser re-melted specimens, the limited martensite transformation proceeded only in C20, C45 and C90 steels. As a result of laser boriding the microstructure of MZ contained additionally iron borides. The specimens with higher dilution ratio value were characterized by higher hardness of re-melted zone. The aim of this study was to indicate the possibility of predicting the microstructure and depths of MZ and HAZ with the usage of Ashby and Esterling model. The influence of carbon concentration in steel on the thickness, dilution ratio and hardness of laser-borided layers was determined.

Fabrication of gradient-structure CuNiBe alloy bars by laser remelting and water-cooling

ABSTRACTLaser remelting (LR) is a typical laser manufacturing technique. In this study, LR was used to fabricate gradient-structured CuNiBe alloy bars. A series of LR experiments with different parameters (such as the output power of the laser transmitter, scanning speed, and cooling condition) and subsequent aging treatments were designed. The remelted zone depth (RZD), the hardness with depth on the plane perpendicular to the LR track, the microstructure, and the precipitation characteristics of different zones of the remelted samples were analyzed. The results showed that the RZD increased with a higher output power of the laser transmitter and lower scanning speed. The hardness of the CuNiBe was significantly improved by the LR and subsequent aging treatment. A remelted zone (RZ) and heat affected zone (HAZ) were found in the remelted surface layer, and equiaxed substructures and columnar substructures were present in the RZ. Well-dispersed NiBe precipitates on the substructure boundaries in the transitional area between the RZ and HAZ were the main cause of strengthening of the sample that underwent LR without water-cooling. The strengthening effect was significantly enhanced by the refined grains for the sample that underwent LR with water-cooling.

Laser Surface Modification of Aluminium Alloy AlMg9 with B4C Powder.

This paper presents the effects of laser treatment (fiber laser YLS-4000) on the microstructure and selected mechanical properties of the surface layer of AlMg (AlMg9) foundry alloy obtained by alloying with boron carbide (B4C). The correlation between laser alloying process parameters and selected properties of the formed layer was discussed. The studies were supported by microstructural analysis of the remelted zone (RZ), heat affected zone (HAZ), undissolved carbide particles, substrate material, and precipitates formed during rapid solidification. Metallographic investigations of the laser-treated layer were performed using optical microscopy and scanning electron microscopy (SEM). The elemental composition and a detailed analysis of chemical composition in micro-areas were carried out using energy dispersive X-ray spectroscopy (EDS). The remelting thickness, heat-affected zone (HAZ), and amount of base material in surface layers were determined. Microhardness tests were performed on transverse cross-sections of the remelted zone to obtain the hardness profiles in the base material (BM), remelted zone (RZ), and heat affected zone (HAZ). The hardness, roughness, and wear resistance measurements showed that the highest tribological properties of the obtained surface layer were achieved using 0.5 Bar protective gas (Ar) during alloying with B4C powder.

Effect of energy density on laser powder bed fusion built single tracks and thin wall structures with 100 µm preplaced powder layer thickness

Laser Powder Bed Fusion (LPBF) is one of the advanced manufacturing technologies used for fabricating near net shaped components directly from CAD model data by selectively melting pre-placed layer of powder in layer by layer fashion. LPBF process is widely researched with layer thickness up to 60 µm and is now commercially deployed for many metallic materials. However, very limited literature is available in public domain for LPBF with layer thickness >60 µm as the process in this window has many challenges in geometry control and reproducibility due to inherent process instability. However, higher layer thickness with larger beam diameter can bring better productivity and shorter built time with limited compromise on minimum feature size. The present work focuses on a systematic parametric study on single track and thin wall fabrication using LPBF at layer thickness of 100 µm by varying laser power (150–450 W) and scan speed (0.02–0.08 m/s) using SS 316L powder. For the range of parameters under investigation, process window yielding stable tracks (regular and uniform) is obtained for energy density between 87.5 and 140 J/mm3. An analytical model for predicting the width of the track and a regression model for the depth of re-melted zone in the substrate subsurface and track area during single track fabrication is developed in terms of energy density. The average difference in predicted and experimental values for width and area of the track are 3.18% and 7.61%, respectively within the process window. Width of thin walls built at the same parameters is measured and the variation between width of thin wall and track is estimated in terms of energy density. The width of thin walls fabricated are observed to be larger than that of single track built at the same combinations of process parameters primarily due to preheating effect. For the range of parameters under investigation, the highest values of width of thin wall and its difference from corresponding width of track is observed at 112.5 J/mm3 in the process window. The study paves a way in understanding the effect of higher layer thickness on the geometry of LPBF built components.

Crystallization behavior of Zr55Cu30Al10Ni5 amorphous alloys produced by selective laser melting of preannealed powders

Selective laser melting (SLM) of Zr55Cu30Al10Ni5 (Zr55) bulk metallic glasses (BMGs) with Zr55 original unannealed powders and annealed powders has been investigated, which is an effort to reveal the influence of crystallization state of powders on the crystallization behavior of remelted zone (RZ) and heat affected zone (HAZ). The as-prepared Zr55 powders consist of amorphous matrix and Al5Ni3Zr2-type phase. When the Zr55 origin powders are annealed at 600 K, 800 K and 1000 K, the microstructure of amorphous matrix is transformed into amorphous, metastable + stable phases and entirely stable phases, respectively. After SLM of these different powders, the gradient microstructure with three crystalline zones (nanocrystal, dendritic eutectic, spherulite) is found from RZ to HAZ for all the deposits. However, the size and density of dendritic eutectic in the top of HAZ is much smaller for the deposits prepared by annealed powders than that by the unannealed powders. In contrast to top of HAZ, abundant multiphase spherulites are formed at the bottom of HAZ for the deposits prepared by the powders with or without annealed. The detailed microstructural and numerical model results reveal that the crystallization at the top of HAZ is mainly dominated by the rapid growth of quench-in clusters or nuclei in RZ, but the crystallization at the bottom of HAZ is controlled by both the nucleation and growth of these clusters or nuclei. It is precisely because the average size of quench-in clusters or nuclei increases but total quantity decreases during annealing, resulting in the increase of thermal stability in RZ and the suppression of crystallization in the top of HAZ for the deposits with annealed powders.

Wear behavior of self-lubricating boride layers produced on Inconel 600-alloy by laser alloying

In this work, laser alloying has been used in order to produce the self-lubricating boride layers on Inconel 600-alloy. The two-step process was used during laser alloying. First, the surface of the substrate material was coated with a paste containing amorphous boron and calcium fluoride CaF2 as a self-lubricating addition. Then, this surface was re-melted by laser beam using TRUMPF 2600 Turbo CO2 laser. The laser beam powers 1.56 kW and 1.95 kW were used for laser alloying. The re-melted zone included dendritic and globular precipitates of nickel, chromium and iron borides among the soft Ni-phase as well as CaF2 particles, locating close to the surface. The microhardness of the re-melted zone, containing solid lubricant, was lower than that of the laser-alloyed layer with only boron. Whereas the wear resistance was higher. The tribofilm was observed on the worn surfaces of laser-alloyed layers with boron and CaF2. The presence of the tribofilm reduced wear of mating parts and improved their tribological properties.

Numerical and experimental investigation on microstructure and residual stress of multi-pass hybrid laser-arc welded 316L steel

In multi-layer welding, the interaction between the weld beads had a great impact on the performance of the overall joint. Therefore, experimental research and thermal-plastic analysis of 316L stainless steel multi-layer hybrid laser-arc welding were performed. The reasonable heat sources were proposed to simulate hybrid laser-arc welding (HLAW) and laser beam welding (LBW). The simulation results of temperature field and residual stress distribution were both validated and in accordance with experimental measurements. On this basis, Combining the simulated results with the metallurgical analysis, the microstructure of multi-layer weld was divided according to temperature histories. The formation mechanism of feathery ferrite precipitated in the re-melting zone (RZ) was analyzed. The feathery ferrite could increase the micro-hardness of the interlaminar position of weld. Moreover, the residual stress along the multi-layer weld thickness direction was simulated and X-ray diffraction (XRD) measured, which indirectly demonstrated the size and orientation variation of the grains in the RZ.

Influence of niobium and molybdenum addition on microstructure and wear behavior of laser-borided layers produced on Nimonic 80A-alloy

Abstract Laser alloying was used for production of thick layers on surface of Nimonic 80A-alloy. For laser surface modification, three types of pre-coated pastes were applied: with amorphous boron, with amorphous boron and molybdenum as well as with amorphous boron and niobium. The microstructure, hardness and wear resistance of produced layers were studied in details. The presence of different types of borides in re-melted zone depended on the paste composition and caused an increase in hardness up to about HV 1000. The wear resistance was evaluated by calculation of mass wear intensity factor Imw and relative mass loss of specimen and counter-specimen. The wear behavior of the tested frictional pairs was determined by 3D interference microscopy, scanning electron microscopy equipped with EDS microanalyzer. The significant increase in abrasive wear resistance was observed in comparison to untreated Nimonic 80A-alloy. The lowest mass loss intensity factor was characteristic of laser-alloyed Nimonic 80A-alloy with boron and niobium (Imw=1.234 mg/(cm2·h)). Laser alloyed-layers indicated abrasive wear mechanism with clearly visible grooves. Laser alloying with boron and niobium resulted in the additional oxidative wear mechanism. In this case, EDS patterns revealed presence of oxygen on the worn surface of specimen.

The Corrosion Studies of Electron Beam Welded Nickel Alloy

The paper presents the influence of electron - beam (EB) remelting effect on the surface layer electrochemical parameters obtained from potentiodynamic anodic polarization studies and impedance spectroscopy measurements for a set of Inconel 617 electron beam remelted obtained for different process parameters. The correlation between EBW process parameters and characteristic of surface oxide layer properties and resistance to the acidic environment were discussed. The electrochemical studies were supported by microstructural analysis of the remelted zone (RZ), heat affected zone (HAZ), native metal and observed precipitates formed under rapid solidification process. Both electrochemical technics applied to evaluate corrosion properties of remelted Inconel 617 evidenced a strong influence of the electron beam current on the corrosion resistance.

Microstructure and Properties of Laser Additive Manufactured Fe-Cr-Ni-B Steel by Divided-area Process

This paper presented a fundamental investigation on the formation mechanism and compatibility of microstructure/mechanical property of Fe-Cr-Ni-B steel samples, which were built by the divided-area forming and integral connection methods. Results indicate that the stress at the edge of the specimen produced in additive manufacturing is reduced by the divided-area forming and integral connection method. According to the microstructure analysis using stereology microscopy/optical microscopy/scanning electron microscope/X-ray diffractometer/Schaeffler diagram, the macrostructure is distributed in strip band geometry and the microstructures consist of dendrites with the intermetallic phases containing austenite phase, boride/matrix eutectic phase. Additionally, the macrostructure strips near the bonding line bend to the building direction and are discontinuous because of the unique forming method. However, the microstructures and composition of the samples are homogeneous. Due to the existence of boride and the finer microstructures, mechanical properties analysis shows that the alloy has high hardness, high ultimate strength and bad deformability. The hardness distribution is homogeneous apart from some positions of the re-melting zone and the heat-affected zone near the bonding line, which have a relatively lower hardness because of differences in microstructure.

Laser Surface Treatment of Cast Aluminium-Silicon Alloys

The reason of performing the investigations carried out in this work was to investigate the microstructure of the laser treated Al-Si-Cu cast aluminium alloy with the ceramic powder particles using High Power Diode Laser (HPDL) for remelting, and/or alloying. First of all the feeding and distribution of the powder in the surface layer of the alloyed and remelted AlSi7Cu material. Very important issue is the determination of the laser treatment parameters, especially the powder feeding rate, laser power, and scan rate to achieve an enhancement of the layer hardness for ensuring this cast aluminium alloy from losing their working properties and to achieve the tool surface is more resistant to wear. The purpose of this work was also to determine technological and technical conditions comparison for the Al2O3 and SiC ceramic powder alloyed into the surface layer with High Power Diode Laser. There are presented also the investigation results about the determination of proper technical condition during the laser treatment, especially the laser head distance and shielding gas influence. The presented results concerns first of all the structure investigation of the obtained surface layer allowing it to achieve an enhanced hardness and wear resistance more resistant for work, special attention was devoted to monitoring of the layer morphology of the investigated material and on the particle occurred. Light (LM) and scanning electron microscopy (SEM) were used to characterize the microstructure of the obtained surface zones - the remelted zone (RZ) and heat affected zone (HAZ), the ceramic powder distribution and intermetallic phases occurred. A wide range of laser power values was applied and implicated with different laser scan rates. The powders in form of ceramic powders used for alloying were chosen with the particle size of ca. 60μm. This study was conducted to investigate the influence carbide and oxide powder addition on structure and mechanical properties as well the and structure changes occurred during the rapid solidification process. The investigation ensures to use laser treatment for alloying/feeding of ceramic powder particles into the surface of light alloys. The scientific reason of this work is the applying of High Power Diode Laser (HPDL) for improvement of aluminium`s mechanical properties, especially the surface hardness. As the main findings was determined that the obtained surface layer is homogeny without cracks and has a comparably higher hardness value compared to non-treated material. The surface hardness increases together with the applied laser power, the highest power applied gives the highest hardness value for the surface. Also the distribution of the ceramic particles is proper, but there a need for further modelling, because the hardness increases in general according to the laser power used so that the highest power applied gives to highest hardness value in the remelted layer, but for other powder amount or alloy the values should be determined separately, and more data would be necessary to create a model for the technique appliance. The practical purpose of this work is to analysis the impact and application possibility of HPDL laser surface treatment on the cast Al-Si-Cu alloys to deliver application possibilities for diverse branches of industry.

气氛保护对灰铸铁激光重熔区气孔的影响

气氛保护对灰铸铁激光重熔区气孔的影响

Modelling of the effects of laser modification of gas-nitrided layer

Purpose: The effects of laser processing parameters on the dimensions of simple laser tracks, produced on the previously nitrided layer, were analysed. Design/methodology/approach: Gas nitriding is one of the most commonly used thermochemical treatment, resulting in many advantageous properties: high hardness, enhanced corrosion resistance, improved wear resistance and fatigue strength. However, an unfavourable increase in the thickness of compound zone (e + g’) close to the surface was observed after conventional gas nitriding. This was the reason for undesirable embrittlement and flaking of the layer. Therefore, a controlled gas nitriding was intensively developed, reducing the percentage of the most brittle e (Fe2-3N) iron nitrides. In this study, the hybrid surface layer was produced. The controlled gas-nitriding was followed by laser heat treatment (LHT). Laser modification was carried out using various laser beam powers and scanning rates. The dimensions of laser tracks (i.e. depths and widths of re-melted zone and heat-affected zone) were measured. Numerical methods were used in order to formulate a mathematical model. Findings: Laser processing parameters (laser beam power and scanning rate) influenced the microstructure obtained. The microstructure of laser modified nitrided steel with re-melting consisted of re-melted zone (MZ), heat-affected zone (HAZ), nitrided layer without visible effects of laser treatment and the substrate. The use of laser beam power of 0.26 kW resulted in only a partial re-melting of the compound zone. The two characteristic values of laser beam power were estimated. P0MZ corresponded to the laser beam power at which the re-melted zone disappeared (i.e. width and depth of MZ were equal to 0). P0HAZ was a value of laser beam power at which the effects of laser irradiation were invisible in microstructure (i.e. width and depth of HAZ were equal to 0). The model was proposed in order to predict the effects of LHT on microstructure. Research limitations/implications: The presented model was limited to the scanning rates in the range of 2.24-3.84 m/min. In the future research, this range should be exceeded, especially, taking into account the lower values of scanning rate. Practical implications: The presented model could be used in order to control the microstructure and properties of hybrid surface layers, obtained as a consequence of the controlled gas-nitriding and LHT. Originality/value: his work is related to the new conception of laser modification of nitrided layers. Such a treatment provided the hybrid layers of new advantageous properties.

Microstructure and wear resistance of gas-nitrided steel after laser modification

Purpose: The aim of this work was to study the microstructure and wear resistance of hybrid surface layers, produced by a controlled gas nitriding and laser modification. Design/methodology/approach: Nitriding is well-known method of thermo-chemical treatment, applied in order to produce surface layers of improved hardness and wear resistance. The phase composition and growth kinetics of the diffusion layer can be controlled using a gas nitriding with changeable nitriding potential. In this study, gas nitriding was carried out on 42CrMo4 steel at 570°C (843 K) for 4 hours using changeable nitriding potential in order to limit the thickness of porous e zone. Next, the nitrided layer was laser-modified using TRUMPF TLF 2600 Turbo CO2 laser. Laser tracks were arranged as the multiple tracks with scanning rate vl=2.88 m/min and overlapping of about 86% using the two laser beam powers (P): 0.21 kW and 0.26 kW. Microstructure was observed by an optical microscope. Phase composition was studied using XRD. Hardness profiles in the produced hybrid layers was determined using a Vickers method. Wera resistance tests were performed using MBT-01 tester. Findings: Gas nitriding resulted in formation of compound zone, consisting of e nitrides close to the surface and a zone, composed of e + g' nitrides. Below the white compound zone, the diffusion zone occurred with nitric sorbite and precipitates of g' nitrides. In the microstructure after laser heat treatment (LHT) of nitrided layer, the zones were observed as follows: the re-melted zone (MZ) with e nitrides, nitric martensite and non-equilibrium FeN0.056 phase, the heat-affected zone (HAZ) with nitric martensite and precipitates of g' phase and the diffusion zone (DZ) without visible effect of laser treatment. Laser beam power influenced the depth of MZ and HAZ, so the thickness of hardened zone. The hardness of MZ was slightly decreased compared to the hardness of compound zone after gas nitriding. However, the significant increase in hardness was observed in HAZ. The formation of hybrid layers advantageously influenced the tribological properties. The laser-heat treated nitrided layers were characterized by improved wear resistance compared to the only gas-nitrided layer. Research limitations/implications: The effect of LHT on the microstructure and properties of gas-nitrided layer was limited to the two laser beam powers. In the future research, this range should be exceeded, especially, taking into account the lower values of laser beam power. It will result in laser modification without re-melting. Practical implications: The selection of suitable LHT parameters could provide the hybrid layers of modified microstructure and improved wear resistance. Originality/value: This work was related to the new concept of modification of nitrided layer by laser heat treatment.

The Effects of Laser Surface Hardening on Microstructural Characteristics and Wear Resistance of AISI H11 Hot Work Tool Steel

AbstractThe present study deals with the effects of laser surface treatment on microstructure evolution and wear resistance of AISI H11 hot work tool steel in quenched and tempered condition. The most upper laser-affected zone is characterized by re-melted microstructure consisting of dendrite cells with fresh non-tempered martensite, retained austenite and inter-dendritic carbidic network. The subsolidus microstructure just beneath the re-melted zone represents the most laser surface hardened zone consisting of fresh non-tempered martensite with fine and coarse carbides as a result of overheating the original QT substrate microstructure. The highest microhardness values in the range from 775 to 857 HV were measured for the LSH microstructure and the most softened microstructure exhibited the minimum hardness of 530 HV. The laser treated samples showed the improvement of their surface wear resistance by 35%.

Formation of face-centered cubic titanium in laser surface re-melted commercially pure titanium plate

Micron-scale face-centered cubic titanium phase (named as δ phase) were noticed in the re-melted zone of laser surface re-melted commercially pure titanium plate. The morphology, sub-structure, orientation and distribution of δ phase were investigated by scanning electron microscopy, electron back-scattered diffraction and transmission electron microscopy. Three kind formation processes of δ phase were put forward based on the investigation. The first one is α′→δ transformation which takes place in single α′ grains and leads to the orientation relationship {001}δ//{0001}α′ <110>δ//<112¯0>α′. The second one is β→α′+δ transformation which takes place at α′/α′ interfaces and leads to the orientation relationship {001}δ//{11¯0}β 〈110〉δ//〈111〉β. The third one is another kind of β→α′+δ transformation that takes place at α′/α′ interfaces and leads to the orientation relationship {11¯1}δ//{11¯0}β<110>δ//<111<β. It is believed that the transformations of δ phase are stress assistant ones and in the present investigation, the phase transformation stress of β→α′ transformation acts as the assistant driving force for the formation of δ phase.

Laser alloying of 316L steel with boron and nickel

Purpose: The aim of the study was to improve the hardness and tribological properties of austenitic 316L steel by laser alloying with boron and nickel. Design/methodology/approach: The relatively low wear resistance of austenitic 316L steel could be improved by an adequate surface treatment. Laser alloying was developed as an alternative for time- and energy-consuming thermo-chemical treatment, e.g. diffusion boriding. In the present study, laser alloying of 316L steel with boron and nickel was carried out as the two-stage process. Firstly, the outer surface of the sample was coated with the paste, consisting of the mixture of boron and nickel powders, blended with a diluted polyvinyl alcohol solution. Second stage consisted in laser re-melting of the paste coating together with the base material. Laser treatment was carried out with the use of the TRUMPF TLF 2600 Turbo CO2 laser. The multiple laser tracks were formed on the surface. The microstructure was observed with the use of an optical microscope (OM) and scanning electron microscope (SEM) Tescan Vega 5135. The phase analysis was carried out by PANalytical EMPYREAN X-ray diffractometer using Cu Ka radiation. Hardness profile was determined along the axis of laser track. Wear resistance was studied using MBT-01 tester. Findings: The use of the adequate laser processing parameters (laser beam power, scanning rate, overlapping) caused that free of cracks and gas pores and the uniform laseralloyed layer in respect of the thickness was produced. In the microstructure, only two zones were observed: laser re-melted zone (MZ) and the substrate. There were no effects of heat treatment below MZ. Heat-affected zone (HAZ) was invisible because the austenitic steel could not be hardened by typical heat treatment (austenitizing and quenching). The produced laser-alloyed layer was characterized by improved hardness and wear resistance compared to the base material. Research limitations/implications: The application of proposed surface treatment in industry will require the appropriate corrosion resistance. In the future research, the corrosion behaviour of the produced layer should be examined and compared to the behaviour of 316L steel without surface layer. Practical implications: The proposed layer could be applied in order to improve the hardness and tribological properties of austenitic steels. Originality/value: This work is related to the new conception of surface treatment of austenitic steels, consisting in laser alloying with boron and some metallic elements.

The effect of laser treatment parameters on temperature distribution and thickness of laser-alloyed layers produced on Nimonic 80A-alloy

Purpose: The aim of this paper was to determine the influence of laser treatment parameters on temperature distribution and thickness of laser-alloyed layers produced on Nimonic 80A-alloy. Design/methodology/approach: In this paper laser alloying was used in order to produce layers on Nimonic 80A-alloy surface. The three types of the alloying materials were applied: B, B+Nb and B+Mo. Microstructure observations were carried out using an optical microscope. The hardness measurements were performed using a Vickers method under a load of 0.981 N. For evaluation of temperature distribution the equations developed by Ashby and Esterling were used. Findings: The produced layers consisted of re-melted zone only and were characterized by high hardness (up to 1431 HV0.1). The increase in laser beam power caused an increase in thickness and decrease in hardness of re-melted zones. The temperature distribution was strongly dependent on laser treatment parameters and physical properties of alloying material. The higher laser beam power, used during laser alloying with boron, caused an increase in layer thickness and temperature on the treated surface. The addition of Mo or Nb for alloying paste caused changes in melting conditions. Research limitations/implications: The obtained results confirmed that laser beam power used for laser alloying influenced the thickness and hardness of the produced layers. Moreover, the role of type of alloying material and its thermal properties on melting condition was confirmed. Practical implications: Laser alloying is the promising method which can be used in order to form very thick and hard layers on the surface of Ni-base alloys. The obtained microstructure, thickness and properties strongly dependent on laser processing parameters such as laser beam diameter, laser beam power, scanning rate as well as on the type of alloying material and its thickness, or type of substrate material. Originality/value: In this paper the influence of alloying material on temperature distribution, thickness and hardness of the laser-alloyed layers was in details analyzed.

Laser borided composite layer produced on austenitic 316L steel

Abstract Abstract Austenitic 316L steel is well-known for its good resistance to corrosion and oxidation. Therefore, this material is often used wherever corrosive media or high temperatures are to be expected. The main drawback of this material is very low hardness and low resistance to mechanical wear. In this study, the laser boriding was used in order to improve the wear behavior of this material. As a consequence, a composite surface layer was produced. The microstructure of laser-borided steel was characterized by only two zones: re-melted zone and base material. In the re-melted zone, a composite microstructure, consisting of hard ceramic phases (borides) and a soft austenitic matrix, was observed. A significant increase in hardness and wear resistance of such a layer was obtained.