The effect of cladding speed on phase constitution and properties of AISI 431 stainless steel laser deposited coatings

Abstract

The effect of cladding speed on phase constitution and properties of AISI 431 stainless steel laser deposited coatings Hemmati, I.; Ocelik, V.; De Hosson, J. Th. M. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Shorter processing time has given impetus to laser cladding technology and therefore in this research the AISI 431 martensitic stainless steel coatings are laser deposited at high cladding speeds, i.e. up to 117 mm/s. The analysis of phase constitution and functional properties of the coatings are performed by optical microscopy, Scanning Electron Microscopy (SEM), and hardness and sliding wear tests. The outcome of this research shows that an extreme refinement of the solidification structure will influence the phase constitution of the coatings by lowering the M s temperature and hence stabilizing the austenite which results in lower hardness values and increased wear rates. These results confirm that the structural refinement obtained by higher cladding speeds is not helpful for improving the hardness and wear properties of laser deposited martensitic stainless steel coatings.

The influence of processing speed on the properties of laser surface deposits

“…Contrary to the case of multi-layer deposits of AISI 431 coatings [13], a decrease in hardness of martensitic 42C deposits with increasing cooling rate was observed. By increasing the cladding speed two general trends in the properties of the 42C coatings were observed: refinement of the solidification structure (smaller cell spacing) and stabilization of retained austenite.…”

“…Hardness of the coatings was measured on transversal cross sections using Vickers indenter at a load of 4.9 N. 3 Results Figure 1 shows the microstructure of three coatings deposited at various speeds, namely 41C, 3533 and MM23 steel. Microstructure observations on 42C coatings did not result in such a clear picture as shown in Figure 1, but an estimate of the average size of the structural units was possible [13]. In Figure 1 one may see that for all these alloys, refinement of the microstructure increases with increasing cladding speed.…”

“…Substantial refinement of austenite dendrites during solidification will increase the energy barrier to martensitic transformation. As a result, the martensite start (M s ) temperature will decrease which will lower the amount of martensite at room temperature [13]. While such a reduction in the amount of martensite was observed for MM23 coatings, substitution of Mo 2 C by the much harder VC compensated for any loss of hardness.…”

Microstructural Analysis of Electron Beam Cladded Surface Layers Using Co‐ and Fe‐Enriched Additives

“…The existence of Cr 7 C 3 cannot be ruled out, however, as partial overlaps of the Cr 7 C 3 peaks with the ferrite and austenite peaks occur, and the phase presumably occurs with such a fine distribution that it cannot be proved to be present with the analytical methods used. Furthermore, because of the high rate of cooling during EB cladding, it is likely that martensite is formed which, because it has the same lattice type, cannot be differentiated from ferrite by X‐ray diffraction methods.…”

Laser Surface Modification — A Focus on the Wear Degradation of Titanium Alloy

“…Higher laser speeds lead to subsequent reduction in the amount of clad material particulates onto working piece leading to a thin clad layer. Hemmati et al investigated into the effect of scanning speed on phase constituents and properties of laser-deposited coatings [41]; the investigation showed a significant refinement of dendritic structure that stabilized the phases and reduced the volume fraction of other phases at higher speeds. Laser cladding technology was used to deposit Co-Ti alloy on mild steel using different scanning velocities [42].…”