Papers by Keyword: Surface Engineering

Abstract: The purpose of this paper was the investigation of laser treatment influence on the microstructure and properties of the surface layer of heat treated Al-Si-Cu cast aluminium alloys, using the high power diode laser (HPDL). The performed laser treatment involves remelting and feeding of ZrO₂ ceramic powder into the aluminium surface. Based on the performed investigations it was possible to obtain the layer consisting of the heat affected zone, transition zone and remelted zone, without cracks and defects as well as has with a slightly higher hardness value compared to the non remelted material. The laser power range was chose as 1.5 to 2.0 kW and implicated by one process speed rate of 0.25 m/min. Also a powder size was used for alloying with the particle size of ca. 100 μm. The hardness value increases according to the laser power used so that the highest power applied gives to highest hardness value in the remelted layer [1-8]. The carried out investigations allow to conclude, that as a result of alloying of the heat-treated cast aluminium alloys with oxide ceramic powder the surface layer can be enriched with the powder particle and in some cases a high-quality top layer is possible to obtain. Very often to determine conditions of laser treatment are being used the numerical methods that would significantly shorten the time to find the most optimal parameters. [8]. Concerning original practical implications of this work there was important to investigate the appliance possibility of High Power Diode Laser (HPDL) for enhancement of the aluminium surface properties, especially the wear resistance and hardness. the scientific reason was also to describe structure changes and processes occurred in the laser remelted surface aluminium layer after ZrO₂ feeding using HPDL laser [10-1. .

Abstract: The investigations results concern the influence of laser heat treatment on the structure and mechanical properties of aluminium alloy, where the mutual relationships were tested and presented in this paper. The aim of this investigations was to improve the mechanical and wear resistance properties of the top surface layers of the aluminium alloy AlSi12CuNiMg by remelting and feeding the tungsten carbide powder in to the molten material and next quick solidification. The powder of tungsten carbide has been introduced in the liquid metal using gravity feeder at a constant rate of 3 g/min. In order to remelting the aluminium alloy surface, there has been used the high power diode laser HPDL, with an applied power of the laser beam in the range between 1.6 kW and 2.0 kW. The linear laser scan rate of the beam was set as much as 0.4 m/min. As a result of laser treatment of aluminium alloy a composite layer with higher hardness and enhanced wear resistance compared to the base material has been obtained.

Abstract: Nitriding steel sample SACM 645 was nitrided by active screen plasma nitriding using a titanium double screen to form simultaneously TiN coatings/nitrogen-diffusion layer on the sample surface. The sample was placed on the sample mount of the various materials (SACM 645, Cu, Ti and SiO₂-Al₂O₃). The sample with the mount was placed on the sample stage in a cathodic potential. A titanium double screen was placed on the cathodic stage around the mount. Active screen plasma duplex processing were performed in 75% N₂ + 25% H₂ atmosphere for 18 ks at 823 K under 100 Pa. In each sample, the hardness of the sample surface was high and beneath compound layer, the hardness decreased rapidly with the distance from the surface, following a flattening of the profile. Wear loss of each duplex-processed sample decreased than that of untreated sample. Particularly, wear loss of the sample using the Ti mount considerably decreased.

Abstract: Bone-like fluoridated hydroxyapatite (FHA) coatings were prepared on Ti-6Al-4V substrates (TC4) by using laser cladding. This bioceramic coating was fabricated by adding CaF2 micron-particles into the hydroxyapatite before presetted on the Ti alloy substrate and radiated by laser beam which aimed at obtaining lower solubility, fine thermostability and maintaining the comparable bioactivity and biocompatibility. Coatings, which were processed using a Nd:YAG laser cladding, presented FHA crystallization on the surface with a uniform morphology along the coating cross-section and no significant dilution of the titanium alloy was observed. Phase analysis by X-ray diffraction indicated the generation of fluoridated hydroxyapatite phase in the laser cladded coatings. The coatings showed the formation of a metallurgically sound and diffused substrate-coating interface, which significantly increased bonding strength between the coatings and subtrate. The bioactive coatings afforded favourable bone bioactivity by inducing the rapid precipitation of apatite on their surface when immersed in a simulated body fluid (SBF). The work demonstrated the potential of using laser cladding for fabricating fluoridated hydroxyapatite bioceramic coatings on Ti alloy.

Abstract: The hot-dip galvanized and hot dip aluminized are widely used surface anti-corrosion technologies in steel beam guardrails region all over the world. Both of coating can not only play the role of landscaping, but also can protect the base metal from being eroded, and greatly extending the life of the guardrails. The appearance quality, process characteristics, corrosion resistance and cost of the two anti-corrosion coating are described in this paper. By analyzing both the similarities and differences between the two anti-corrosion technologies and their application advantages, we hope to provide some references on choosing the surface anti-corrosion technology.

Abstract: In the present work, chitosan (CHI) and elastin-like recombinamers (ELRs) were used to conceive nanostructured thin films driven by sequential electrostatic layer-by-layer (LbL), a simple and versatile technique that discards the use of harmful reagents. Two similar ELRs were engineered to contain negatively charged aminoacids and organized and a single monoblock or a triblock. The buildup of the films was monitored in real time using a quartz-crystal microbalance with dissipation monitoring (QCM-D). Wettability transitions were observed from a moderate hydrophobic surface to an extremely wettable upon increasing the temperature to 50 °C, accompanied by topography changes at the nanoscale as assessed by atomic force microscopy (AFM). Furthermore, the dependence on time for the surface molecular rearrangement was studied for the films with each ELR. The potential of this technology may stimulate the development of devices and biomaterials for biomedical applications in the near future, such as surfaces with tunable and patterned cell adhesion, while the use of ELRs will allow developing polypeptides with biological significance.

Abstract: Low plasticity burnishing (LPB) is a new method of surface improvement, which raises the burnishing to the next level of sophistication. LPB can provide deep compression for improved surface characteristics. The study focuses on the surface roughness, micro-hardness and surface integrity aspects on soft AISI 420 STAVAX ESR martensitic stainless steel AISI 420 material. This material is pronounced as difficult to cut materials like titanium, Inconel 718 etc. The investigation of surface integrity was done on this materials in terms of operating parameters like sliding speed, feed rate and depth of penetration (DOP) identifying the predominant factors among the selected parameters. The steel balls used were cryogenically treated at sub zero temperature of -176 degrees. Sub-surface micro-hardness study were also done to asses the depth of compression altered zone, surface roughness and surface hardness. The process can be applied to critical components effectively as the LPB process has cycle time advantages and also low investment cost. This can be also realized by introducing on high speed machines. This process was studied by using cryogenically treated different ball diameters at various operating parameters. This also improved on concentricity of work material. More the depth of compression produced low surface roughness at low sliding speed, feed rate with larger ball diameter. The DOP also helps to improve on surface and sub-surface hardness and close roundness. There are limitations on DOP beyond which the surface deteriorated.

Abstract: Exploring and using surface engineering technology into the Anti-aging antibacterial mold of mulberry silk brocade fabrics through multiple dipping and padding to carry out limited permeation and effective bonding strength on material surface. It has obvious effect on antibiotic action and less effect on the silk materials’ original performance.

Abstract: The nano-indentation response and the friction and wear properties of the CNx/SiC (carbon nitride /silicon carbon) double layer thin films (SiC films as interlayer) deposited on nanocrystalline titanium substrate using magnetron sputtering technique at room temperature were investigated. The results show that the CNx films exhibited a low nano-hardness of 8.0 GPa and Young's modulus of 55.0 GPa but a high hardness-to-modulus ratio of 0.146. As sliding against Si₃N₄ (silicon nitride) ball under Kokubo simulation body fluid (SBF) at room temperature, the CNx films exhibited the superior tribological properties with the friction coefficients of about 0.1 and the special wear rate of about 1.6×10⁻⁶ mm³/Nm.

Abstract: The work presents a summary of previous studies on fatigue crack propagation within various Aluminum alloys. The effective characteristics on crack growth are first highlighted and the influence of surface engineering such as polishing, shot peening and skimming to enhance the failure resistance are discussed. Several different existing developed models for predicting the rate of crack propagation are compared in terms of incorporated effective parameters. Finally numerical and computational analyses as the accurate, fast and cheap methods which have attracted the Engineers’ interest are reviewed and compared with other methods.