France’s Technical Centre for Mechanical Industry (Cetim) has released a new steel grade for the Laser Powder Bed Fusion (L-PBF) Additive Manufacturing of parts which can reportedly undergo nitriding treatment. According to Cetim, the new grade has been added to the list of steels used in AM and the organisation has characterised the 33CrMoV12 steel for the production of parts via L-PBF Additive Manufacturing as part of its R&D work carried out on behalf of French manufacturers.
The organisation stated that with its high carbon rate and nitriding capability, this steel offers attractive mechanical properties and opens up new application possibilities, especially in the power transmissions sector. It joins the three steels already commonly used for L-PBF manufacturing: X2CrNiMo17-12-2 (316L) and X5CrNiCuNb16-4 (17-4PH) stainless steels and the X2NiCoMo18-9-5 steel (maraging 300).
Cetim explained that although these three steels can be easily welded due to their low carbon levels (approximately 0.05%), the same is not true for the 33CrMoV12 grade, which can have a carbon percentage as high as 0.36%. Therefore, the powder for this type of material, must be pre-heated before L-PBF, making the manufacturing process more troublesome.
Cetim believes that even though some AM systems have a pre-heating system, in most cases the pre-heating temperature is insufficient, being around 200°C and falling below the required 500°C. With a view to limiting and possibly eliminating this operation, one solution is to specifically determine the laser fusion parameters.
The organisation’s study was carried out in conjunction with Volum-e, a polymer and metal prototyping and Additive Manufacturing specialist located in à Blangy-sur-Bresle (Seine-Maritime, France). By finely adjusting the parameters of the process, the two partners state that they were able to create test specimens and a demonstrator in the studied steel by L-PBF.
Cetim reportedly continued the work by minutely examining the parts including: chemical analysis of the material, porosity rates, residual stresses, influence of the heat treatment on the mechanical strength (tension and bending), capacity for nitriding, fatigue strength, etc. The organisation states that the assessment of this study reveals that the steel 33CrMoV12, can be worked by L-PBF exhibiting mechanical performance that is higher than that of the same steel when laminated, and due to its nitriding capability, its scope of use ranges to heavily surface loaded parts.