Optimization of the Deposition Parameters of HVOF FeMnCrSi+Ni+B Thermally Sprayed Coatings

Abstract

HVOF thermal spray process produces coatings with low porosity and low oxide content, as well as high substrate adhesion. Small variations on the parameters of the HVOF process can generate coatings with different characteristics and properties, which also is chemical composition depended of the alloy. FeMnCrSi alloy is a cavitation resistant class of material with a great potential for HVOF deposition use. The main goal of this article is to study the influence of some HVOF parameters deposition, as standoff distance, powder feed rate and carrier gas pressure on three different alloys. FeMnCrSi experimental alloys with some variations in nickel and boron content were studied. Taguchi experimental design with L9 orthogonal array was used in this work. Porosity, oxide content, tensile adhesion strength and microhardness of the coatings were evaluated. The results indicated that all factors have significant influence on these properties. Chemical composition of the alloys was the most important factor, followed by the carrier gas pressure, standoff distance and powder feed rate. The addition of Ni, produces coatings with lower levels of oxide content and porosity. An experiment with improved parameters was conducted, and a great improvement on the coating properties was observed.

Welding and Thermal Spray Processes for Maintenance of Hydraulic Turbine Runners: Case Studies

“…Lamana, Pukasiewicz, and Sampath [24] studied the mechanism of cavitation by the detachment of WC particles sprayed by HVOF (High-Velocity Oxy-Fuel) with kerosene and propylene fuels. Sucharski et al [35] optimized the HVOF parameters standoff distance, powder feed rate, and carrier gas pressure to improve the properties of FeMnCrSiNi alloys [33], reaching the porosity 0.05%, oxide content 8.94%, tensile adhesion 40.29 MPa, and microhardness 366 HV. With the same alloys, Silveira et al [36] indicated the influence of the feedstock powder size distribution on the cavitation resistance, reaching an erosion rate of 7.8 mg/h with powders -45 µm.…”

Thermal Spraying of FeMnCrSi Alloys: An Overview

“…Sucharski et al [31] evaluated the influence of the HVOF process parameters on the morphology of FeMnCrSi coatings, changing the standoff distance, powder feed rate, and carrier gas pressure. The porosity increased with the standoff distance and decreased with the powder feed rate.…”

Characterization of Fly Ash and a Protective Coating for Brazilian Thermal Power Plant Boilers

“…The quality and durability of coatings can be improved by parameter optimization of the spraying process, preparation of substrate surface for better adhesion, and automation of the process 27 . In addition, the melting conditions and structure of coatings by electric arc spraying depending on the pressure of spraying airflow, spraying angle, speed, work distance, and others, which can result in controlling the amount of the oxide phase and porosity in coatings, and mechanical characteristics like hardness, residual tensile stresses, cohesion and adhesion 13,15 .…”

“…The arc spraying process has a high deposition rate and a lower operating cost than other similar processes and the possibility of application and maintenance in-field operation. The main mechanism of adhesion and cohesion of coating is the mechanical anchoring of the splats [13][14][15][16] .…”