Adhesion of HVOF-Sprayed WC-Co Coatings on 316L Substrates Processed by SLM

W Tillmann,K.-P Hoyer,K.-U Garthe,C Schaak,M E Aydinöz,M Schaper,J Liß,L Hagen

doi:10.1007/s11666-020-01081-y

W Tillmann, K.-P Hoyer + Show 6 more

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https://doi.org/10.1007/s11666-020-01081-y

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Abstract

Different studies have been demonstrated that the surface integrity of substrate bulk materials to be coated has a significant impact on the adhesion of thermally sprayed coatings. It is known that the surface integrity of parts processed by selective laser melting (SLM) differs from those obtained from bulk materials. Although 316L stainless steel is among the most investigated material for SLM, the adhesion of thermally sprayed coatings on 316L stainless steel substrates processed by SLM has not been studied yet. This study aims at evaluating the effect of various mechanical pre-treatments onto 316L stainless steel substrates processed by SLM and their effect on the adhesion of high velocity oxy-fuel (HVOF)-sprayed WC-Co coatings. To differentiate between topographical effects and residual stress-related phenomena, a stress-relief heat treatment of the SLM substrates served as a reference throughout the investigations. The differently pre-treated SLM substrates were investigated with regard to the surface roughness and residual stresses. For the HVOF-sprayed SLM composites, Vickers interfacial indentation tests were conducted to assess the resulting coating adhesion. The findings demonstrated that the HVOF-sprayed WC-Co coatings predominantly exhibit good adhesion to the SLM 316L substrates. However, it was found that the stress state in the SLM 316L substrate surface is more likely to affect the adhesion of the WC-Co coating, while the substrate surface roughness showed a marginal effect.

Highlights

Scarce raw material resources, high CO2 emissions, stricter environmental regulations, as well as the reduction in energy costs are of great interest
This study aims at evaluating the effect of various mechanical pre-treatments onto 316L stainless steel substrates processed by selective laser melting (SLM) and their effect on the adhesion of high velocity oxy-fuel (HVOF)-sprayed WCCo coatings
It could be shown that the HVOF-sprayed WC-Co coatings predominantly exhibit sufficient adhesion to the differently pre-treated 316L substrates processed by SLM

Summary

Introduction

Scarce raw material resources, high CO2 emissions, stricter environmental regulations, as well as the reduction in energy costs are of great interest. The demand for future-oriented and economical manufacturing processes continues to increase. Regarding the production of one-off prototypes or parts (i.e., in small batches), and complex components, additive manufacturing processes are more than ever in the focus of interest. This is caused by the demand for a high degree of design freedom concerning the component geometry, combined with short production times. Due to the inherent process characteristics (Ref 2), the produced samples still exhibit a residual porosity and high surface roughness. The resulting microstructural characteristics (e.g., grain orientation) and residual stresses (Ref 3), among others, depend on the thermal history during processing, which in turn is associated with the building strategy

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