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In this study, the particle velocity and spatial distribution of a plastic abrasive jet were modeled for the removal of surface coatings from a new generation of ship hulls by plastic abrasive jet machining. The particle velocity in the jet has been accurately tested through high-speed photography. It was found that the particle velocity of plastic abrasives with the same particle size was larger than conventional abrasives. Downstream from the nozzle exit axis, the divergence profile of the abrasive jet is approximately linear at distances up to 6.2dN; at distances higher than 6.2dN, the divergence profile line of the abrasive jet is approximately “flared”. The particle velocity of the plastic abrasive increased with increasing jet pressure, and no significant decrease of particle velocity was found in the limited measurement range. The instantaneous velocity distribution of the particles has been discussed in terms of axial and radial directions along the jet. For the radial velocity distribution of the abrasive jet, a relatively steady state is observed in the cross-section of the jet near the nozzle outlet. The results of the model calculations are in accordance with the experimental test data in terms of both tendency and margin of change.

Erosion equations were developed to predict the material removal of polyurethane coatings on carbon fiber reinforced plastic (CFRP) surfaces and validated through experimental data. The effects of abrasive properties, process parameters, and organic coating properties (such as fracture toughness and hardness) were considered in the equations. As the erosion angle increased, elastoplastic deformation in the oblique direction and repeated "deformation" in the normal direction were the main reasons for material removal. The ductile erosion behavior was confirmed by experimental data because the maximum erosion rate occurred at an incident angle of 30°. The coefficient and index in the equations were determined by experimental data, and the equations were verified. The developed equations could accurately predict the quantity loss of organic coatings under different particle sizes and particle velocities, and the erosion equations were in good agreement with the experimental data.

ABSTRACTThe paper aims to research the effect of rare earth elements on the carbonitriding layer of titanium alloy by establishing a theoretical model between rare earth concentration and atomic diffusion efficiency. It shows that adding rare earth can not only refine the discharge holes, but also reduce surface cracks, which significantly improve the surface quality of the strengthening layer. It is also found that an appropriate amount of rare earth can greatly increase the growth rate of the carbonitriding layer and carbon content near the surface. Furthermore, compared with the conventional plasma electrolytic carbonitriding treatment, adding 2 g L−1cerium oxide can effectively reduce the activation energy of carbon, so as to improve its diffusion ability.

The paper aims to research the effect of rare earth elements on the carbonitriding layer of titanium alloy by establishing a theoretical model between rare earth concentration and atomic diffusion efficiency. It shows that adding rare earth can not only refine the discharge holes, but also reduce surface cracks, which significantly improve the surface quality of the strengthening layer. It is also found that an appropriate amount of rare earth can greatly increase the growth rate of the carbonitriding layer and carbon content near the surface. Furthermore, compared with the conventional plasma electrolytic carbonitriding treatment, adding 2?g?L-1cerium oxide can effectively reduce the activation energy of carbon, so as to improve its diffusion ability.

•The fabrication of the amino thermoset plastic (ATP) abrasive is developed.•ATP abrasive in abrasive jet polishing (ATP-AJP) of aluminum alloys is developed.•The abrasive embedding phenomenon can be resolved in ATP-AJP of aluminum alloys.•A different ductile erosion mechanism in AJP of ductile materials is found.

Electrochemical machining is a promising method for titanium alloy processing. The polarization characteristics of Ti6Al4V were studied in detail in order to provide a deeper understanding of this method. The polarization curve of the alloy, which shows the relationship between current density and potential under an external electric field, was obtained in NaBr electrolyte at three different concentrations in a three-electrode electrochemical test system. The surface topography of the polarization zone and pits was examined by scanning electron microscopy, and their fractal features were calculated by the picture point cover method. The results show that Ti6Al4V in the more concentrated electrolyte has higher dissolution rate, lower decomposition potential, and more uniform surface topology in the polarization areas.

The Ti(C,N)–TiB2–Co cermet tool was developed using reactive hot pressing sintering technology. The orthogonal test method was used to study the cutting performance of the tool when cutting 304 austenitic stainless steel at high speed. The relationship between cutting parameters and cutting force, work hardening layer depth and surface roughness was studied by range analysis method. The results show that the cutting surface roughness increases with the increase of feed rate, and the correlation between cutting depth and cutting speed is not obvious. The depth of hardened layer is mainly affected by feed rate and cutting depth. When the feed rate f= 0.1 mm/rev, the cutting thickness ap = 0.2 mm, the cutting speed v= 150 m/min, the surface roughness and the depth of the hardened layer are the smallest. Then, the cutting performance of this cutting parameter is compared with that of commercial cemented carbide tools. The results show that the cermet tool has lower roughness, smaller hardened layer depth and better adhesive wear resistance, which is mainly due to the excellent hardness and wear resistance of the cermet tool.