Fabrication and Characterization of Zr Microplasma Sprayed Coatings for Medical Applications

Abstract

This paper presents new results of studying the influence of parameters of microplasma spraying (MPS) of Zr wire on the structure of Zr coatings. The coating experiments were accomplished in a two level fractional factorial design. Individual particles of sprayed Zr wire and their splats on the substrate were collected under various spraying parameters (amperage, spraying distance, plasma gas flow rate and wire flow rate) and evaluated by Scanning Electron Microscopy (SEM) to establish the effect of particle size and shape on the coating microstructure. The particles were characterized by measurement of their sizes and the obtained results were evaluated in terms of their degree of melting. This was compared with the experimentally observed coating microstructure type and finally correlated to the investigated coating porosity to select the specific MPS parameters of Zr coatings depositing onto medical implants from Ti alloy. It was found that the main parameters influencing the size of the sprayed Zr particles and the porosity of the Zr coatings are the plasma gas flow rate and amperage. It was demonstrated that it is possible to control the porosity of Zr microplasma coatings in the range from 2.8% to 20.3% by changing the parameters of the MPS. The parameters of microplasma spraying of Zr wire were established to obtain medical implant coatings with porosity up to 20.3% and pore size up to 300 μm.

Research of the structure and mechanical properties of microplasm porous coatings for biomedical purposes

“…However, with an increase in the porosity of such coatings, the decrease in the modulus of elasticity is less intense, compared to the coatings applied by the MPS method. Thus, according to the work [18], the coating made of the VT1-00 alloy, obtained by the powder sintering method, had a modulus of elasticity of 37.7 GPa with a porosity of 28.6 %, while according to the work [3], the coating made of the same alloy, applied by the method MPS, even with a porosity of 13.7 %, had a modulus of elasticity in the range of 35. 4-38.5 GPa.…”

“…It is known that the modulus of elasticity of coatings depends on the porosity of the material [2]. Thus, reducing the difference between the modulus of elasticity of the bone and the implant is possible with the application of a porous coating on the surface of the implant by the method of microplasma spraying (MPS) [3], as the modulus of elasticity of such coatings can decrease by more than an order of magnitude, compared to the original sprayed material, depending from the mode parameters of sputtering [4].…”

A Brief Review of Current Trends in the Additive Manufacturing of Orthopedic Implants with Thermal Plasma-Sprayed Coatings to Improve the Implant Surface Biocompatibility

“…This allows for the production of coatings on thin-walled and small-sized parts without deformation or overheating. Additionally, MPS enables the creation of porous coatings on metal endoprostheses using refractory and biocompatible metals (such as Ti, Ta, and Zr) [14][15][16][17]78,84], and their alloys, as well as ceramics such as HA [15,16,19,78,79]. These porous coatings contribute to improved biocompatibility and promote the secondary fixation of the implant by facilitating bone tissue ingrowth into the pores.…”

“…First, the coating experiments for MPS of wire materials such as unalloyed zirconium [17,84,92] and pure titanium [14,15], as well as synthesized HA powder [15,79], were accomplished in a two-level fractional factorial design (2 4−1 ). The following parameters were chosen as variable parameters: current (I, A), plasma gas flow rate (Q, slpm), spraying distance (H, m), and wire or powder flow rate (V w , m/s or V pow , g/min).…”

“…For each combination of parameters in eight runs, the porosity of the coating, as well as the sizes and morphology of individual particles and splats forming the coating, were studied by scanning electron microscopy and analysis of the corresponding digital images. For example, Figure 4 shows the dependence of the particle size of the microplasma-sprayed Zr wire and the porosity of the coatings on the combination of MPS parameters in runs 1-8 with SEM images of Zr particles [84].…”