Microstructural Analysis and Tribological Behavior of AMDRY 1371 (Mo–NiCrFeBSiC) Atmospheric Plasma Spray Deposited Thin Coatings

Mădălina Simona Bălţatu,Cornelia Cîrlan Paleu,Bogdan Istrate,Viorel Paleu,Shubrajit Bhaumik,Corneliu Munteanu,Petrică Vizureanu

doi:10.3390/coatings10121186

Mădălina Simona Bălţatu, Cornelia Cîrlan Paleu + Show 5 more

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https://doi.org/10.3390/coatings10121186

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Abstract

Water treatment plants include a set of pumping stations, and their mechanical components experience various wear modes. In order to combat wear, the mechanical components of the pumps are coated with various types of wear resistant coatings. In this research, AMDRY 1371 (Mo–NiCrFeBSiC) coatings were deposited with the atmospheric plasma spray (APS) method on parallelepipedal steel samples manufactured from a worn sleeve of a multistage vertical irrigation pump. In order to find an optimum thickness of AMDRY 1371 coatings, the samples were coated with five, seven and nine passes (counted as return passes of the APS gun). Mechanical properties of the coating (microhardness and Young’s modulus) were determined by micro-indentation tests. An AMSLER tribometer was used to investigate the wear resistance and wear modes of the coated samples in dry conditions. A mean coefficient of friction (CoF) of around 0.3 was found for all the samples, but its evolution during the one hour of the test and also the final wear volumes and wear rates depended on the thickness of the coating. To estimate the roughness of the surfaces and the wear volumes, measurements were carried out on a Taylor Hobson profilometer. In order to understand the nature and evolution of wear of coatings of various thicknesses, the unworn and worn surfaces of the coated samples were analyzed by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The wear modes of the coatings were studied, emphasizing the coating removal process for each sample. According to our results, for each dry friction application, there is an optimum value of the thickness of the coating, depending on the running conditions.

Highlights

Pumps are the heart of any water treatment plant
Results on air plasma sprayed Mo coatings were reported by Sampath and Wayne [15], recommending the addition of Mo2 C to NiCrFeBSi powder for improved kinetic friction properties
Various types of Mo–NiCrFeBSiC coatings were proposed by Sampath and Vanderpool [17] and the values of the dry coefficient of friction (CoF) obtained by tests on a ball-on-disc tribometer were very high, the lowest

Summary

Introduction

Pumps are the heart of any water treatment plant. Their mechanical components, such as impellers, rolling bearings, seals, bushes, and sleeves, suffer severe damage due to various wear mechanisms: corrosion, abrasion, adhesion, erosion, cavitation, pitting etc. One of the ways to combat such kind of combined wear is by coating the surfaces with wear resistant powders. These powders can be Coatings 2020, 10, 1186; doi:10.3390/coatings10121186 www.mdpi.com/journal/coatings. Azarmi et al [1] optimized the deposition parameters for the APS process of 625 Ni-based superalloy, emphasizing that the oxidation index and the melting index incorporate all the parameters that were found to be significant in the statistical analyses and correlate well with the measured oxide content and porosity in the coatings. Rico et al [2]

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