Abstract
A model to predict the conditions for printability is presented. The model focuses on crack prevention, as well as on avoiding the formation of defects such as keyholes, balls and lack of fusion. Crack prevention is ensured by controlling the solidification temperature range and path, as well as via quantifying its ability to resist thermal stresses upon solidification. Defect formation prevention is ensured by controlling the melt pool geometry and by taking into consideration the melting properties. The model’s core relies on thermodynamics and physical analysis to ensure optimal printability, and in turn offers key information for alloy design and selective laser melting process control. The model is shown to describe accurately defect formation of 316L austenitic stainless steels reported in the literature.
Highlights
In additive manufacturing (AM), printability defines the ability of a feedstock to be successfully deposited on a substrate as a bulk material, avoiding significant defects, whilst acheiving desired mechanical properties [1]
Powder bed fusion (PBF) processes can be divided into selective laser melting (SLM) and electron beam melting (EBM)
As 316L alloy is an industrially relevant austenitic stainless steel due to its wide application, here we focus on the cracking behaviour of this type of steel
Summary
In additive manufacturing (AM), printability defines the ability of a feedstock to be successfully deposited on a substrate as a bulk material, avoiding significant defects, whilst acheiving desired mechanical properties [1]. There is no comprehensive modelling approach to predict the formation of different types of porosity for different SLM parameters in austenitic stainless steels. Numerous studies attempted to correlate the volumetric energy (heat input), which is the ratio between laser power P and scan speed v, layer thickness t and hatch distance h, to form porosity [25,26,27] This expression does not consider the effects of material properties, and other process parameters such as laser spot size. Printability has traditionally been determined by trial and error experiments, so as to identify regions of successful material deposition This approach is effective in producing high quality parts, but ignores the complex relationships between the thermal, physical, mechanical, chemical, and metallurgical processes involved. The proposed approach is validated with literature results, testing the methodology presented in this paper for the printability of a defect-free austenitic stainless steel
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