Search Results (3)

To address the challenge of fabricating metal-based composite coatings on the inner surfaces of tubular and internal hole components, a novel cylindrical electro-spark powder deposition (CEPD) technique is introduced. Utilizing the CEPD process, Ni-based composite coatings are successfully prepared on the inner surface of 316L stainless-steel tubes. The resultant Ni-based composite coatings completely covered the inner surface, exhibiting a splattered morphology and forming a robust metallurgical bond. Microstructural analysis revealed that the composite coatings primarily consisted of submicron-sized fine dendrites, with the main phases identified as Ni, FeNi₃, and Fe₃Ni₂, in addition to Ag particles. These fine grains and reinforcing phases contributed to a substantial increase in coating hardness, with an average value of 673.33 HV, representing approximately 2.82 times the hardness of the substrate. Tribological testing indicated that the high-hardness Ni-based composite coatings nearly doubled the surface wear resistance of the substrate and exhibited a significantly lower friction coefficient. Compared to other existing inner surface coating techniques, the CEPD process offers simplicity, low cost, and the ability to produce functional composite coatings with complex compositions. The prepared coatings exhibit considerable development potential and may offer a novel approach for the advancement of coating techniques for non-line-of-sight surfaces. Full article

Friction Stir Extrusion (FSE), the focus of this research, is a process that has tremendous potential for shaping and improving the mechanical properties of the final product as well as the mechanical alloying. In this study, a cylindrical sample of LM13 aluminum, to which silicon powder is added, is extruded by the penetration of a tool and takes the shape of a tube. The microstructure of the aluminum tube produced is studied using a light microscope. Various tests, including compression and wear tests, are performed to evaluate the wear and mechanical properties of the tubes produced. Additionally, the process is simulated using the finite element method (FEM), and the strain and temperature distributions in the tubes are examined to understand the impact of tool advancing speed better. The strain and temperature are highest on the inner surface, where the tubes meet the tool. Moreover, as the advancing speed increases from 25 to 40 mm/min, the maximum temperature in the tubes increases from 350 to 400 °C. The surface quality of the samples is directly related to the advancing speed, so the surface quality improves as the advancing speed increases. The results obtained from the compression and wear tests show that the compression strength has increased by about 17%, and the wear resistance has improved by about 20%. Full article

The influence of the number of passes and the tube materials on the microstructural evolution, mechanical properties, and wear behavior of Cu and brass tubes after parallel tubular channel angular pressing (PTCAP) was investigated. The grain size decreased to final grain sizes of 138.6 nm and 142.7 nm, after PTCAP of the Cu and brass tubes was conducted in up to 4 and 2 passes, respectively. PTCAP contributes to obtaining an ultra-fine grain (UFG) microstructure, with a mixture of different grain sizes that conferred high hardness. The present results indicate the superior wear resistance of Cu and brass PTCAP tubes, relative to Cu and brass samples that were previously deformed by different severe plastic deformation (SPD) processes. The wear mechanism of the Cu tubes changed from delamination and cracks with a high degree of adhesive wear before PTCAP into a combination of adhesive and abrasive wear, with a decrease in the presence of oxygen content after the PTCAP procedure. The wear mechanism also changed from a combination of adhesive and abrasive mechanisms into abrasive ones with the absence of oxygen after the PTCAP of brass tubes. Full article