Effects of remelting processes on porosity of NiCrBSi flame sprayed coatings

Abstract

In the current study, image analysis technique was used to determine and compare the porosity level and characteristics of the pore size and shape of the flame sprayed NiCrBSi coatings before and after remelting processes. The effect of remelting temperature on the shape and size distribution was investigated by image analysis using SEM images. Remelting processes were carried out at 950, 1000, 1050 and 11008C. The obtained results revealed that remelting process decreased the porosity level (from 11.7 to 1.9%) and improved the metallurgical bonding between the carbon steel substrate and the coating. The pores shape in the as sprayed sample was an irregular, elongated shape. More than 55% of pores were sharp disc shaped. After the remelting process, the pore shape was converted to a near spherical and non-flat spheroidal configuration.

Tribo-performance analysis of HVOF sprayed 86WC-10Co4Cr & Ni-Cr2O3 on AISI 316L steel using DOE-ANN methodology

“…Murugan et al (2014) studied the different parameters of WC-10Co4Cr HVOF coating on the naval brass substrate to optimize the hardness and porosity using a response surface methodology. Karimi et al (2016) deposited NiCrBSi powder using the flame spray technique to improve porosity. They reported that high porosity helped prevent the formation of the erosion pit.…”

Thermodynamics and Mechanics of Thermal Spraying of Steel EN 10060 Substrate with NiCrBSi Alloy after Milling

“…Similar work was done by Planche et al [ 19 ], who, moreover, compared the NiCrBSi powder prepared by plasma, flame, and the HVOF process. The remelting of NiCrBSi coatings achieved by the HVOF technology ensures a reduction of the porosity, and, consequently, it leads to the improvement of the mechanical and microstructure properties [ 20 ]. Machining of thermal-sprayed layers is a great challenge for many new companies, in particular for machining surfaces that are difficult to machine.…”

Caracterización de recubrimientos NiCrBSiMo depositados por rociado térmico por flama usando diferentes parámetros de depósito

“…Combustion flame spraying technique is commonly used to deposit a wide range of materials, including Ni-based self-fluxing alloys, due to its low-cost, practical aspects and few environmental issues (Rodríguez et al, 2003;Navas et al, 2006;González et al, 2007a;Amokrane et al, 2011;Culliton et al, 2013;Karimi et al, 2016). Despite the above mentioned advantages; low particle velocity in flame spraying affects the microstructure and behavior of the coatings (Planche et al, 2005).…”

“…In order to overcome such shortcomings and improve coatings quality; it is important to optimize the spraying parameters and to establish a correlation between the deposition variables and the resultant coatings characteristics. To date, previous investigations reported the microstructure and properties of flame sprayed coatings under a set of working conditions (González et al, 2007b;Culliton et al, 2013;Karimi et al, 2016) without further analysis about the optimization and correlation between the spraying parameters and coatings properties. Therefore, the aim of the present investigation is to analyze the effect of three process variables namely: standoff distance, flame chemistry, and nozzle diameter, on the porosity content, hardness, and thickness of as-sprayed coatings, and to determine the processing conditions that allow the deposition of coatings with minimal microstructural defects using a more economical technique.…”