Effect of spraying parameters on the microstructural and corrosion properties of HVAF-sprayed Fe–Cr–Ni–B–C coatings

A Milanti,V Matikainen,H Koivuluoto,G Bolelli,L Lusvarghi,P Vuoristo

doi:10.1016/j.surfcoat.2015.07.018

A Milanti, V Matikainen + Show 4 more

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https://doi.org/10.1016/j.surfcoat.2015.07.018

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Abstract

Thermally sprayed Fe-based coatings have been extensively studied as future solution in order to replace more expensive, harmful and environmentally dangerous Ni- and WC-based coatings for several industrial applications where high corrosion and wear resistance are required. The aim of the present study is to investigate the effect of spraying parameters on the microstructure and the corrosion resistance of Fe-based coatings manufactured with the High Velocity Air Fuel (HVAF) thermal spray process. Six sets of thermal spraying parameters have been chosen and their effect on the overall quality of coatings was investigated. All HVAF coatings showed comparably dense microstructure with near-zero oxidation, proving the high quality of the deposition process. However, higher anti-corrosion and mechanical properties were achieved by increasing the spraying air pressure and decreasing the particle feeding rate without altering the thickness and the overall deposition rate. Powder feeding rate was reported to have a remarkable effect on microstructure and corrosion properties. Coatings with beneficial compressive residual stresses were successfully obtained by increasing air pressure during spraying which resulted in improved microstructural and corrosion properties.

Highlights

Thermal spraying is a widely spread coating technology process employed in several industrial applications
The powder feeding rate of samples 2, 4 and 6 is nearly twice as large as those of samples 1, 3 and 5; one can state that the deposition efficiency of samples sprayed with the same parameters (1/2, 3/4 and 5/6) but with different powder feeding rate is comparable proving the high versatility of the High Velocity Air Fuel (HVAF) process
Kuroda et al [38] have reported higher particle velocity when dealing with higher air pressure in HVAF spray process

Summary

Introduction

Thermal spraying is a widely spread coating technology process employed in several industrial applications It consists of molten, semi-molten or solid particles accelerated by a high speed stream of gases towards a substrate in order to form a thick coating [1]. High chromium content is designed in order to provide chromium for hard precipitates and on the other hand to provide chromium dissolved in the austenitic solid solution matrix in order to increase the ability to form a thin protective oxide layer. Such design is meant to increase the corrosion resistance of the alloy without altering the mechanical properties [5]. Ni- and WC-based materials have been lately pointed out as potential lung disease and carcinogenic agents and responsible of skin diseases (eczema, allergen), asthma and pneumoconiosis [6] [7]

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