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Ti—6Al—4V alloy powder was processed by electrode induction melting gas atomization (EIGA) at high gas pressure (5.5–7.0 MPa). The effects of atomizing gas pressure on the powder characteristics and the microstructure, along with the mechanical properties of the as-fabricated block by laser melting deposition (LMD), were investigated. The results indicate that the diameters of powders are distributed in a wide range of sizes from 1 to 400 μm, and the median powder size (d50) decreases with increasing gas pressure. The powders with a size fraction of 100–150 μm obtained at gas pressures of 6.0 and 6.5 MPa have better flowability. The oxygen content is consistent with the change trend of gas pressure within a low range of 0.06%–0.20%. Specimens fabricated by LMD are mainly composed of α+β grains with a fine lamellar Widmanstatten structures and have the ultimate tensile strength (UTS) and yield strength of approximately 1100 and 1000 MPa, respectively. Furthermore, the atomized powders have a favorable 3D printing capability, and the mechanical properties of Ti—6Al—4V alloys manufactured by LMD typically exceed those of their cast or wrought counterparts.

A Fe60 alloy coating was deposited on the surface of Q235 steel by semiconductor laser under the different preheating temperature at 25°C, 100°C, 150°C, 200°C, 250°C, 300°C respectively. The structure and hardness of the samples were analyzed by the means of OM、SEM、XRD、micro-hardness tester. The results show that: A Fe60 alloy coating with high Cr and C content was prepared on the steel substrate by using optimized process parameters, the interface bonding was formed between the coating and the substrate, the thickness of the coating without cracks and porosities is about 6-10mm. There are equiaxed and dendrite crystals in the coating and the phase of coating is composed of α-Fe, γ-Fe,{Fe,Ni} solid solution, Fe3C, Cr2B, Cr7C3. Preheating treatment has good eliminating coating cracks role in the laser deposited Fe-based coating with high Cr and C content, the sample preheated at 200°C has the finest crystalline structure, and the thickness is 8mm and the hardness is up to 806HV. Preheating treatment is an effective method to eliminate the cracks in the high thickness Fe60 alloy coating by laser direct deposition.

In situ synthesized TiBx/TiC reinforced composite coatings were prepared on Ti-6Al-4V substrate by laser in situ deposition using 10B4C-18TiNi-72Ti-6Al-4V (wt. %) powder blends as the feedstock materials. The microstructural analysis of the composites was performed using scanning electron microscope, and phase analysis was done with X-ray diffraction. The results showed that the composite coatings contained long needle TiB, irregular block TiB2 and disperse particles/dendrites TiC, the thick rod phase which was a inlay structure consisted of TiB2 and TiC. These composite reinforced phases were evenly distribution in the (TiNi+Ti2Ni+α–Ti) substrate.

B4C/TiNi mixed powders with different composition (10B4C+90TiNi and 20B4C+80TiNi in wt. %) prepasted on Ti-6Al-4V substrates were scanned by a FL-Dlight02-3000W semiconductor laser to obtain TiBx+TiC reinforced graded composite coatings. The influences of the processing parameters on the microstructure of the coatings were studied. Optimal processing parameters were obtained with laser power (P) 1700W/1900W, laser scanning speed (V) 6.67mm/s and defocus length 310mm. The microstructures and phases of the coatings were analyzed with OM, SEM and XRD respectively. Graded composite coatings with in-situ synthesis of TiC, TiB and TiB2 reinforcements in the matrix of Ti2Ni and TiNi were obtained.

Using 663-tin bronze, Ni, W, nanoAl2O3, MoS2, graphite, CaF2, and Ni coated graphite as the matrix alloy powder, in which copper-coated carbon fiber of 5%, 7%, 9%, 11% and 13% in volume fraction were added as the reinforcing phase, a novel type carbon fiber/copper-matrix self-lubricating composite materials was prepared by means of powder metallurgy. The results indicate that the mechanical properties of the composite materials are improved after adding copper-coated carbon fibers. The composite materials reach optimal overall mechanical performance under testing when the volume fraction of the added copper-coated carbon fibers is 11%.: with a hardness of 57.8 HV and a compressive strength of 222 MPa. The addition of carbon fiber also improved the friction and wear properties of the composite materials. Increasing the volume fraction of fiber, was found to increase the wear resistance and improve self-lubricating performance. A volume fraction of 11% gave a friction coefficient of 0.09 and abrasion loss of 4mg.

The targets are micron-sized TiO2 powders and micron-sized Ag powders, TiO2@Ag nanocomposite particles with core-shell structure were synthesized by pulsed laser gas phase evaporation-liquid phase collecting method. The morphology, structure and synthesis mechanism of the samples were studied by means of transmission electron microscopy (TEM), energy dispersive spectrometer (EDS), and X-ray diffraction technique (XRD). The results show that the pure TiO2 nanoparticles sol was firstly prepared as liquid phase collecting system using gas phase evaporation-liquid phase collecting method; then, the target was changed using Ag, and TiO2 @ Ag nanocomposite particles with core-shell structure, which are spherical or ellipsoidal, were successfully synthesized under certain conditions of laser synthesis parameters; the diameters of most TiO2@Ag nanocomposite particles covering synthesized after 2h range from 15nm to 35nm, the diameters of most TiO2 @Ag nanocomposite particles covering synthesized after 4h range from 25nm to 50nm, and the size of nanocomposite particles increases with the increase of covering synthesis time; TiO2 nanoparticles synthesized previously in liquid phase function as crystallized cores, while Ag atoms and their clusters are adsorbed to TiO2 surfaces and surround the surfaces to form TiO2 @ Ag nanocomposite particles.

A novel graphite/copper alloy-based self-lubricating composite materials were prepared using the powder metallurgy method by composing 663 bronze, Ni, W, nanoAl2O3, MoS2, Ag, CaF2, Sm2O3 as the basic alloy powder and adding 1wt.%, 1.5wt.%, 2wt.%, 2.5wt.%, 3wt.% graphite and nickel coated graphite powder respectively to the composite powder. The microstructure, mechanical properties and friction properties of the samples were studied. The results show that the samples with nickel coated graphite powder have their wettability and the composite structure between graphite and copper alloy matrix is improved. When the content of graphite is 3wt.%, the properties of samples prepared by Ni-coated graphite are improved compared with those prepared by uncoated graphite. The hardness is increased from 34HV to 38HV, the crushing strength is from 116MPa to 151MPa, the friction coefficient is reduced from 0.28 to 0.21, wear loss is reduced from 20mg to 12mg. The samples prepared by Ni-coated graphite have good self-lubricating performance.

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.

In this paper, a three-dimensional dynamic simulation model is established for a laser heating process taking into account heat flow by conduction and a temperature dependent specific heat capacity in the material. An unorthodox laser beam profile is characterized by two simple beam shape parameters in the model; the difference in energy distributions between the centre and outer edge of the beam and between the leading and trailing edges of the beam is varied by an adjustment of these parameters. In this way, laser surface heating with unorthodox beam profiles is simulated and studied using COMSOL Multiphysics finite element modeling software.

Ti-6Al-4V, C and TiB2 powders (71.5%Ti-6Al-4V+ 26.2%TiB2+2.3%C in wt. %) were prepasted and then laser clad on Ti-6Al-4V substrates. Laser cladding was carried out with a Nd:YAG pulse laser with the parameters of defocus length 15mm, pulse frequency 15Hz, scanning speed 2-4mm/s, electric current 200-240A. Microstructure and phases were analyzed with the Optical Microscopy(OM), Scanning Electron Microscopy(SEM) and X-Ray Diffraction(XRD). Laser cladding layers with smooth surfaces, good metallurgical bonding with no cracks and pores were formed. The average thickness of the coatings is approximately 80μm. Reactions among Ti, C and TiB2 in the laser molten pool cause in-situ synthesis of TiB, TiB2 and TiC reinforcements. The average microhardness is 836HV, which is more than twice that of the Ti-6Al-4V substrate (320HV). Friction coefficients of the cladding coatings fluctuate between 0.26-0.3. Laser cladding specimen with powder mixture of 71.5%Ti-6Al-4V+ 26.2%TiB2+2.3%C (weight loss 0.0007g after sliding 245m) possesses better wear property than that of the specimen with powder mixture of 90%Ti-6Al-4V+ 10%B4C (weight loss 0.0068g).

Anodic oxide films were prepared firstly on the surface of a 2024 aluminum alloy. Then the effect of different heat-treatment temperatures on the structure and properties of the films was studied. The results indicate that the construction units of Al2O3 oxide film were composed of tubules less than 100nm in external diameter, and the film became more compact and uniform as a result of the increased temperature after the heat treatments of 100, 150, 200, 250, 300, 350, and 400°C under the protection of a H2 atmosphere. The hardness of the films increased linearly with the increase of heat treatment temperature; whereas the wear loss tended to decrease first and then increase. After being treated at the temperature of 250°C, the hardness reaches 606HV, the wear loss is a minimum of 11mg. The structure of the film heat-treated at 250°C has a compact structure, higher hardness, and the best wear resistance.

Two kinds of mixed powders:Ti-6Al-4V/B/C and Ti-6Al-4V/B4C which are pre-pasted or synchronized fed on Ti-6Al-4V substrates separately were scanned by a 500W pulsed YAG laser to induce in situ formation of titanium composite coatings contained TiBxand TiC ceramic reinforced phases. The influences of laser processing parameters including Pulse Frequency (PF), Pulse Width (PW), Laser Power (P) and Scanning Speed (V) together with the powder proportions on the microstructure and properties of the coatings were investigated. Microstructures, phase components of the coating were analyzed by OM, SEM, TEM and XRD respectively. Experimental results show that two and more kinds of ceramic reinforcements were in situ formatted in the matrix of Ti-6Al-4V. TiB and TiC ceramics were formed evenly with the morphology of needle, tiny dendrites and disperse particles in the prepasted single path specimens. For the powder feed laser cladding layers, the ceramic reinforcements were TiB (needlelike), TiB2(hexagonal prism or rodlike), a small amount of TiC (disperse particles) and non fully reacted B4C. The microhardness increased with the increase of the amount of B4C and B+C additions. When the added B and C contents are the same, the microhardness of the coating with B4C addition is higher than that of the coating with B+C addition. The average micro-hardness of a powder prepasted (with 20 wt.% B4C addition) multi-path laser cladding layer formed under the optimized processing parameters is up to 800HV, which is more than 2 times of that of the substrate (340Hv), and the wear weight loss of the layer decreased nearly 3 times that of the substrate.

Two kinds of mixed powders:Ti-6Al-4V/B/C and Ti-6Al-4V/B4C which are pre-pasted on Ti-6Al-4V substrates separately were scanned by a 500W pulsed YAG laser to induce in situ formation of titanium composite coatings contained TiBx and TiC ceramic reinforced phases. The influences of laser processing parameters including Pulse Frequency (PF), Pulse Width (PW), Laser Power (P) and Scanning Speed (V) together with the powder proportions on the microstructure and properties of the coatings were investigated. Microstructure, phase components and micro-hardness of the coating were analyzed by OM, SEM, TEM, XRD and micro-hardness tester respectively. The optimized processing parameters of a single path laser scanned specimen in this case are as follows: PF: 15Hz, PW: 3ms, for the Ti-6Al-4V/B4C specimens the laser line energy ~12.5J/mm, for the Ti-6Al-4V/B/C specimens the laser line energy ~11J/mm. TiB and TiC ceramic were formed evenly reinforced in the matrix of Ti-6Al-4V with the morphology of needle, tiny dendrites and disperse spherical particles. The maximum micro-hardness of single-path layers is up to 750 Hv, which is over twice of that of the substrate (367Hv).The wear weight loss decreased nearly 3 times that of the substrate.

The Fe 3 Si based coating was produced on the Fe-1Si steel surface by a pulsed Nd:YAG (yttrium aluminum garnet) laser. Its phase constitution and microstructure were characterized by using X-ray diffraction (XRD), optical microscope (OM), and field emission scanning electron microscope (FESEM) with associated energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM). The hyperfine structure of the coating was studied by Mossbauer spectra (MS) and the magnetic property was also measured at room temperature by a vibrating sample magnetometer (VSM). The obtained coating is pore and crack-free with dense microstructure and high Si content. The metallurgical bonding between the coating and the substrate was realized. The microstructure of the coating is typical fine dendrites. The major phase was confirmed by XRD and TEM to be the ordering D0 3 structured Fe 3 Si phase. In addition, there were smaller amounts of the Fe 5 Si 3 phase and the γ-Fe phase in the coating. Compared with the substrate, the laser cladding coating has a lower saturation magnetization and a higher coercive force. The poor magnetic property might be because of rapid solidification microstructure and phase constitution in the coating.