In the design of L-DED (laser-directed energy deposition) cladding processes, the chemical composition of the metallic powders is typically assumed to match that of the intended coating. However, during the deposition of the first layer, dilution with the substrate alters the weld metal composition, deviating from the nominal powder chemistry. Although the application of multiple layers can gradually reduce this dilution effect, it introduces additional complexity and processing time. This study proposes an alternative strategy to counteract substrate dilution from the very first deposited layer, eliminating the need for multilayer coatings. Specifically, to achieve a corrosion-resistant monolayer of AISI 316L stainless steel on a high-strength, quenched-and-tempered AISI 4140 steel substrate, a dilution-compensating alloy powder is added to the standard AISI 316L feedstock. Single-layer coatings, both with and without compensation, were evaluated in terms of chemical composition, microstructure, and corrosion resistance. The results show that unmodified coatings suffered a chromium depletion of approximately 2 wt.%, leading to a reduced pitting potential of Ep = 725 ± 6 mV in synthetic seawater. In contrast, the use of the compensation alloy preserved chromium content and significantly improved corrosion resistance, achieving a pitting potential of Ep = 890 ± 9 mV.

A multilayer laser-deposited lining of AISI 316L stainless steel makes a regular structural steel surface corrosion resistant in physiological media. Despite the application of single-layer stainless-steel linings being economically beneficial and allowing thinner surface modifications, dilution effects that modify the pitting resistance of the coating must be accounted for. In order to study the feasibility of employing single-layer coatings instead of multilayer coatings for corrosion protection in physiological media, a polarization testing back-to-back comparison was performed between laser-deposited AISI 316L monolayers on 42CrMo4 quenched and tempered steel and cold-rolled AISI 316L sheet in Dulbecco’s Phosphate Buffer Solution at 36 °C. A higher dispersion in pitting resistance, ranging from 800 mV to 1200 mV, was found on the coated samples, whereas the cold-rolled material was more stable in the 1200 mV range. The resulting differences in corrosion rates and pitting potentials open the discussion on whether the chemical composition deviations on AISI 316L dilution layers are acceptable in terms of surface functionality in medical devices.