Influence of MAX-Phase Deformability on Coating Formation by Cold Spraying

Andreas Elsenberg,Luca Lusvarghi,Alexander List,Alessia Bruera,Frank Gärtner,Thomas Klassen,Giovanni Bolelli,Marco Busato

doi:10.1007/s11666-020-01110-w

Abstract

As solid-state deposition technique avoiding oxidation, cold gas spraying is capable of retaining feedstock material properties in the coatings, but typically fails to build up coatings of brittle materials. Ceramic MAX phases show partial deformability in particular lattice directions and may thus successfully deposit in cold spraying. However, deformation mechanisms under high strain rate, as necessary for cohesion and adhesion, are not fully clear yet. A MAX-phase deposit only builds up, if the specific mechanical properties of the MAX phase allow for, and if suitable spray parameter sets get realized. To investigate the influence of material properties and deposition conditions on coating microstructure and quality, three MAX phases, Ti3SiC2, Ti2AlC and Cr2AlC, were selected. Up to ten passes under different spray parameters yielded Ti2AlC and Cr2AlC coatings with thicknesses of about 200-500 µm. In contrast, Ti3SiC2 only forms a monolayer, exhibiting brittle laminar failure of the impacting particles. In all cases, the crystallographic structure of the MAX-phase powders was retained in the coatings. Thicker coatings show rather low porosities (< 2%), but some laminar cracks. The deposition behavior is correlated with individual mechanical properties of the different MAX-phase compositions and is discussed regarding the particular, highly anisotropic deformation mechanisms.

Highlights

MAX phases attract increasing attention with respect to possible applications due to their unique property combination of covalently bonded ceramics and metals in one crystal structure (Ref 1)
As compared to the other MAX-phase powders under investigation, the lower impact velocities and higher impact temperatures of Ti3SiC2 particles are due to their larger sizes
The comparison demonstrates that, within this parameter regime, particle impact velocities and temperature are increased by about 90 m/s and 250 °C, respectively

Summary

Introduction

MAX phases attract increasing attention with respect to possible applications due to their unique property combination of covalently bonded ceramics and metals in one crystal structure (Ref 1). The crystallographic structure of the MAX phases with atomic metal layers stacked in between covalent ceramics enables electrical conductivity and a good machinability (Ref [2, 3]). The general formula Mn?1AXn describes the composition with M as an early transition metal (Ti, Zr, Cr...), A as an IIIA-group element (Si, Al...) and X as carbon or nitrogen (Ref 8). By their high melting temperature and the ability. MAX phases are usually synthesized by thermal reaction from the different elemental powders (Ref 12)

Results

Discussion

Conclusion