Metallurgical Soldering of Duplex CrN Coating in Contact with Aluminum Alloy

Pal Terek,Aleksandar Miletić,Lazar Kovačević,Branko Škorić,Janez Kovač,Aljaž Drnovšek

doi:10.3390/coatings10030303

Pal Terek, Aleksandar Miletić + Show 4 more

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https://doi.org/10.3390/coatings10030303

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Abstract

Coatings deposited by physical vapor deposition (PVD) significantly reduce the wear of high pressure die casting tools; however, cast alloy soldering still has a strong negative effect on production efficiency. Although a lot of research has been already done in this field, the fundamental understanding of aluminum alloy soldering toward PVD coatings is still scarce. Therefore, in this work the performance of CrN duplex coatings with different roughness is evaluated by a modified ejection test performed with delayed (DS) and conventional casting solidification (CS). After the ejection tests, sample surfaces and layers were subjected to comprehensive characterizations of their morphological and chemical characteristics. Considerably lower values of the ejection force were recorded in DS experiments than in CS experiments. Surface roughness played an important role in the CS experiments, while samples with different surface topographies in the DS experiments performed in a similar fashion. The decrease in the ejection force, observed in DS tests, is attributed to the formation of a thick Cr–O layer on CrN coating which reduced soldering and sliding friction against thick Al–O casting scale. The Cr–O layer formed in DS experiments suffered from diffusion wear by cast alloy. The observed oxidation phenomena of nitride coatings may be utilized in a design of non-sticking coatings.

Highlights

High pressure die casting (HPDC) is a technology used for the mass production of near-net shape parts of non-ferrous alloys, with thin walls and smooth surfaces
Similar ejection force was measured in delayed casting solidification (DS) experiments on samples of different roughness
The ejection force in DS experiments is reduced when compared to casting solidification (CS) experiment, and there is a clear the ejection force in DS experiments is reduced when compared to CS experiment, and there is a clear trend between the level of reduction and surface roughness, with the highest reduction observed for trend between the level of reduction and surface roughness, with the highest reduction observed for the post-polished sample

Summary

Introduction

High pressure die casting (HPDC) is a technology used for the mass production of near-net shape parts of non-ferrous alloys, with thin walls and smooth surfaces. Due to the ever-increasing application of lightweight components in automotive products and other products, the use of HPDC technology for the production of aluminum alloy castings is constantly expanding This kind of large volume production is economically justified only by highly efficient production of high-quality parts. During operation die (tool) surfaces are exposed to wear by: erosion, corrosion and soldering, thermal cycling fatigue [1,2], and adhesion [3]. These processes affect the tool life and casting quality, but more importantly they increase the production costs due to increased: machine down times, number of rejected castings [3,4], energy and materials consumption. In order to Coatings 2020, 10, 303; doi:10.3390/coatings10030303 www.mdpi.com/journal/coatings

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