Effect of microplasma spraying parameters on the loss of sprayed Zr wire and coating porosity

Abstract

The article presents new results of studying the causes of material loss during microplasma spraying (MPS) and substantiates the choice of optimal parameters for efficient spraying of zirconium wire coatings on steel substrates and obtaining coatings with the desired porosity up to 20.3% on a titanium alloy. Optimum spraying parameters provide the maximum material utilization coefficient (MUC) - up to 95%, and the minimum material losses when spraying coatings on small parts: 47% when spraying onto a substrate with an average cross-sectional area of ​​2 mm and less than 1% when spraying onto a substrate with an average diameter of 8 mm. The studies were carried out using a multifactorial experiment with fractional replicas 24-1 with varying such spraying parameters as current strength, spraying distance, plasma-forming gas flow rate, and wire flow rate. To study the distribution of the coating material in the spray spot, macro photography of the metallization figures was carried out and analyzed with the construction of approximating curves. Scanning electron microscopy was used to determine the pore size and porosity of zirconium coatings at different parameters of microplasma spraying on a titanium alloy. Using the methods of regression analysis of the experimental results, equations were obtained that make it possible to assess the degree of influence of the parameters of microplasma spraying on the value of the MUC and the porosity of the coatings, and it was found that the greatest influence is exerted by the current strength and the plasma-forming gas flow rate. The choice of the optimal MPS parameters of a zirconium coating with a porosity suitable for medical implant coatings has been substantiated.

Keywords

• microplasma spraying (mps)
• zirconium coatings
• material utilization coefficient (muc)
• porosity
• metallization figure