Influence Of Different Heat Treatments On Mechanical Properties, Corrosion Resistance And Polishability For LPBF Manufactured Stellar® X15TN Stainless Tool Steel

Stellar^®X15TN (1.4123/ASTM F899) is a nitrogen alloyed, cobalt free 0, 4% C martensitic stainless steel which is easy to print by LPBF despite its relatively high carbon content. The steel combines a capability to be heat treated to over 58 HRC with an excellent corrosion resistance and a good polishability. Being magnetic and relatively soft in its as built and stress relieved state it is easy to machine, which is necessary for example for drilling and threading of fixation holes. The fact that it is cobalt free is another important feature due to health concerns. Therefore, Stellar^® X15TN is suitable for additive manufacturing of plastic injection molds with conformal cooling, surgical tools, cutting tools for food and pharma processing but also for other components where a combination of high hardness and corrosion resistance is requested such as bearing and valve components. Nitrogen enhances the hardness and the wear resistance of the material through formation of carbonitrides. It is also an austenite stabilizing element that reduces the martensite start (Ms) and finish (Mf) temperatures which improves the printability. Finally, nitrogen has a positive impact on corrosion resistance. The challenge is to add nitrogen and to not lose it during the additive manufacturing. Previous studies have exposed the printing parameters. This work presents different heat treatments and their impact on the main usage properties such as hardness and impact strength.