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Titanium is a highly operational alloy for use in dental implants. Surface inertness of the titanium alloy surfaces reduces osseointegrate, raising concerns about implant loosening. Hydroxyapatite (HA)-rich porous titanium surfaces with moderated surface roughness have better osteoconductivity. This study focused on the surface alteration of Ti6Al4V via hydroxyapatite mixed electric discharge-assisted centerless turning (HA-mixed-EDCLT) to find the optimum surface. The experiments were planned based on a four-factor, three-level Box-Behnken design. HA-powder concentration (Cp), revolutions per minute (RPM), duty factor and impulse current (IP) were the input parameters. The Ra value of machined surfaces ranged from 1.12$\mu$m to 1.63$\mu$m, which is in the bone growth supportive implants range. The average hardness reached 415.8–962.7HV, where untreated surfaces’ hardness was $340\pm 6$HV. Porous, hydrophilic coating with a high Ca, P, and O content deposited on the implant surfaces supports the biocompatibility of implants. Analysis of the elements and compounds shows that the machined surface layer is rich with Ca₃(PO${}_4{)}_2$ and TiO${}_{2,}$which improves the bioactivity of the alloy.

In order to improve the poor comprehensive performance of aluminum bronze surface, a duplex surface modification technology consisting of laser cladding and followed by plasma nitriding was adopted to prepare the infiltration composite modified layer. The effects of different surface treatment techniques on the microstructure and properties of the modified layer were investigated. The results show that the laser cladding surface is mainly composed of Cu-rich intermetallic compounds, and the AlN layer appears on the surface after plasma nitriding treatment, which significantly improves the hardness and tribological properties. The surface modification treatment changes the surface morphology. The microhardness of the alloy surface after composite modification is much higher than that of untreated and single treatment. It is about six times that of the Cu-Al matrix. At the same time, the composite modified layer has a lower friction coefficient and wear volume, showing excellent tribological properties. These research results can provide a new way for the surface design and development of metal materials.

Aluminum (Al) and its alloys are attractive for a variety of applications due to its advantages like light weight, ease of processing, and high thermal/electrical conductivities. However, it suffers short comings in terms of strength, wear resistance, and corrosion resistance. Thermal spray processes are widely used techniques for the surface property improvement like thermal, wear, and corrosion resistances of aluminum and other light metals. This paper summarizes the recent developments in thermal spraying and related technologies. Plasma spraying, flame spraying, and arc spraying are the chief thermal spraying techniques, whereas the HVOF and D-gun processes are the derivatives of flame spraying process. The cold spraying technique is an emerging coating technique where the particles are heated to a temperature lower than their melting point travel at high velocity and coat on impact with the target material by plastic deformation. Different parameters like heat source characteristics, coating material properties, substrate properties, and spray torch operating circumstances affect the coating microstructure and properties.

Extensive progress in brass alloys has been done in surface properties and microstructure. Ti-ion implantation is studied for its effects on electrical resistivity, hardness and microstructure by using scanning electron microscopy, X-ray diffractometer, four-point probe apparatus and Vickers microhardness tester. Ion distribution profile and stopping powers were calculated by Stopping and Range of Ions in Matter (SRIM) code. Nonuniformity in shape, and agglomeration of defects were observed at the surface in SEM micrographs. XRD analysis of (2 0 0) plane for crystallite size, strain, stress and dislocation density is also done. The peak intensity of (2 0 0) is found to be increased by increasing the ion fluence and tensile stresses were also found generated. Increase in the lattice parameter values from 3.681 Å to 3.686 Å appeared as a change in crystallite size, which, in turn, caused an increase in hardness. An increment in electrical resistivity from 7.9$\mu \mathrm{\Omega }$ to 18$\mu \mathrm{\Omega }$ (127.85%) is also observed. For a maximum ion fluence of $2.4\times 10^{14}$ ions/cm², the surface turned out to be amorphous, which helped in making the brass more reliable in its practical usage.

In the present work, an investigation has been made into the electrical discharge machining process during machining of precipitation hardening stainless steel PH17-4. Taguchi method is used to formulate the experimental layout, to analyze the effect of each process parameter on machining characteristics and to predict the optimal choice for each electrical discharge machining process parameters namely, peak current, pulse on time and pulse off time that give up optimal process performance characteristics such as material removal rate, surface roughness, tool wear rate and surface hardness. To identify the significance of parameters on measured response, the analysis of variance has been done. It is found that parameters peak current and pulse on time have the significant affect on material removal rate, surface roughness, tool wear rate and surface hardness. However, parameter pulse off time has significant affect on material removal rate. Confirmation tests are conducted at their respective optimum parametric settings to verify the predicted optimal values of performance characteristics.

Burnishing is a chipless cold working finishing process, by which smooth and workhardened metallic surfaces can be produced. In this paper, an attempt has been made to study the effect of the number of tool passes on surface characteristics and fatigue life of cast Al-Cu components. The conducted experimental work shows, that improvements in surface roughness and fatigue life can be achieved by the application of this process. The increase in the surface hardness and the depth of workhardened subsurface layers of the considered cast alloy were also studied.