A coating of pure titanium without defects was successfully prepared on the surface of Ti-6Al-4V substrate by pulsed laser cladding. The characteristics and performance of the coating and the substrate including microstructure, phase constitution and hardness were probed by combined use of multiple characterization methods. Results show that fine lamellar grains are formed in the coating during the ultrafast non-equilibrium solidification process induced by pulsed laser cladding. The average size of these grains is about 0.79 μm. The hardness test shows that the hardness of the coating is 433.82 HV, 30.4% higher than that of the Ti-6Al-4V substrate. Besides, a lower wear volume compared to the substrate is found for the coating which indicates greatly improved wear resistance. In-depth analyses suggest that the improved surface performance can be mainly attributed to grain refinement strengthening in the cladding zone.

Microstructure and properties of pure titanium coating on Ti-6Al-4V alloy by laser cladding

Metallic materials are among the most crucial engineering materials widely utilized as biomaterials owing to their significant thermal conductivity, mechanical characteristics, and biocompatibility. Although these metallic biomedical implants, such as stainless steel, gold, silver, dental amalgams, Co-Cr, and Ti alloys, are generally used for bone tissue regeneration and repairing bodily tissue, the need for innovative technologies is required owing to the sensitivity of medical applications and to avoid any potential harmful reactions, thereby improving the implant to bone integration and prohibiting infection lea by corrosion and excessive stress. Taking this into consideration, several research and developments in biomaterial surface modification are geared toward resolving these issues in bone-related medical therapies/implants offering a substantial influence on cell adherence, increasing the longevity of the implant and rejuvenation along with the expansion in cell and molecular biology expertise. The primary objective of this review is to reaffirm the significance of surface modification of biomedical implants by enlightening numerous significant physical surface modifications, including ultrasonic nanocrystal surface modification, thermal spraying, ion implantation, glow discharge plasma, electrophoretic deposition, and physical vapor deposition. Furthermore, we also focused on the characteristics of some commonly used biomedical alloys, such as stainless steel, Co-Cr, and Ti alloys.

https://www.mdpi.com/2079-6412/12/10/1459/pdf?version=1666594981

Recent Advancements in Surface Modification, Characterization and Functionalization for Enhancing the Biocompatibility and Corrosion Resistance of Biomedical Implants

Tribological characteristics of the dual titanium boride layers (TiB2+TiB) on titanium alloy

In the present study, the combination of ultrasonic burnishing and heat treatment were applied on a laser cladded Fe-based coating. Besides ultrasonic burnishing at room temperature (UB), two combination strategies of ultrasonic burnishing and heat treatment were explored, i.e. ultrasonic burnishing at a medium temperature (ultrasonic warm burnishing, UWB), and UWB coupled with continuous heat treatment for a period of time (ultrasonic warm burnishing coupled with heat treatment, UWB/HT). Total four samples were prepared and experimentally investigated. Comparing with untreated (control) sample, the surface properties of the three differently treated samples were improved to varying degrees, where the sample subjected to UWB/HT process acquired the best one. UWB/HT Process declined the roughness and porosity of Fe-based coating by 87.86%, 65.41%, and the hardness increased by 34.88% compared to that of control sample, respectively. The residual stress and microstructure of UWB/HT sample also acquired a largest improvement. In addition, the UWB/HT Fe-based coating exhibited the best wear resistance. Summarily, UWB/HT is considered to have the greatest potential to achieve the effective treatment of laser cladding with excellent surface properties over the other two strategies, which is expected to further advance the application of laser cladding technique particularly in the fabrication of some high-demand products serving in harsh conditions.

Improving surface properties of Fe-based laser cladding coating deposited on a carbon steel by heat assisted ultrasonic burnishing

The effect and mechanism of ultrasonic vibration on the microstructure and performance of laser cladding 316L coating has been studied, providing a theoretical basis and technical support for the application of the ultrasonic-assisted laser cladding process. The results show that ultrasonic vibrations with different amplitudes can effectively improve the macroscopic forming quality of the cladding layer, among which the ultrasonic vibration with 17.5 μm amplitude is the best. Ultrasonic vibration can also significantly improve the micro-forming quality of the cladding layer, such as homogenizing the structure, refining grains and reducing porosity. The wear mechanism of the cladding layer with an ultrasonic assistance of 17.5 μm is mainly abrasive wear, so the wear resistance has been significantly improved. The ultrasonic-assisted cladding layer exhibits significant passivation behavior in 3.5 wt% NaCl solution. It may be that the surface roughness reduction and grain refinement caused by ultrasonic assistance can improve the integrity and compactness of the cladding layer, so the dynamic equilibrium process of the dissolution and reformation of the passive film is changed, which can improve the corrosion resistance of the surface. There are some equiaxed grains in the columnar-grains area of the ultrasonic-assisted cladding layer, mainly because the inside of some primary columnar grains has gone through a process of lattice distortion → dislocation multiplication → substructure rotation → formation of small-angle grain boundary → misorientation accumulation → formation of new grains in the process of ultrasonic-assisted laser cladding of 316L stainless steel. 

Effect and action mechanism of ultrasonic assistance on microstructure and mechanical performance of laser cladding 316L stainless steel coating

A roller tip was utilized in a set of self-fabricated ultrasonic burnishing equipment. Ultrasonic roller burnishing with/without heat treatment was proposed and investigated in the surface strengthening of TC11 titanium alloy material. Experimental research together with finite element analysis were carried out to perform the study. Three treatments, including conventional turning, ultrasonic roller burnishing at ambient temperature (URB) and ultrasonic roller burnishing at medium temperature (URB/HT), were comparatively evaluated in term of surface integrity and corrosion resistance of the treated sample. As a result, compared with URB, the surface of TC11 alloy treated by URB/HT had better surface finishing, which significantly improved corrosion resistance, and thus the surface of TC11 alloy was strengthened. The good performance of URB/HT was attributed to the combined effect of the high frequency dynamic impact from URB and the thermoplastic effect of the heat treatment. Owing to the excitation of the ultrasonic vibration during URB, an oscillating stress wave formed and propagated deep inside the being treated material, and the heat treatment in URB/HT case was supposed to accelerate this sort of stress propagation. Meanwhile, both the heat treatment and the dynamic oscillating stress wave facilitated the deformation of the surface layer.

Surface characteristics and corrosion behavior of TC11 titanium alloy strengthened by ultrasonic roller burnishing at room and medium temperature

Surface integrity enhancement of austenitic stainless steel treated by ultrasonic burnishing with two burnishing tips

https://link.springer.com/content/pdf/10.1007/s43452-020-00153-8.pdf

Chonghai Xu

Papers

Surface characteristics and corrosion behavior of TC11 titanium alloy strengthened by ultrasonic roller burnishing at room and medium temperature

Improving surface properties of Fe-based laser cladding coating deposited on a carbon steel by heat assisted ultrasonic burnishing

Surface integrity enhancement of austenitic stainless steel treated by ultrasonic burnishing with two burnishing tips

New approach towards the machining process after laser cladding