a) about which fcc material you are talking?

b) how big is the grain size compared to the hardness indenter?

I would expect that the interface of additively manufactured samples are in genera much weaker that casted material.

Hello Mr. Roshan Sebastian,

in my opinion may be because the material has some small-sized pores? The die cast material has of course more dense structure.

By the way 400 HV is already pretty high may be you are at the limit of the ductility of the material. Because the ductility is responsible for typical depression zone that you want to observe. It cannot be strictly connected to fcc or bcc type directly. Only if bcc is brittle and fcc is ductile in case of your material.

Best regards,

Anton

Mr Nolze, I made a small mistake in the answer. We were comparing Additively manufactured Inconel and Cast Iron alloys. Inconel region is fcc and it had the depressions associated with it, but the Cast Iron region was fine dendritic in an Austenite matrix and its hardness was over 400 HV, showing no depressions around it. Hope it clarifies.

In that case I have a similar opinion like Anton. The grain boundaries are not that perfect so that I would expect a lower hardness for Inconel. Moreover...as far as I remember, Inconel shows precipitation hardening. In order to get a similar microstructure you need a special heat treatment to form gamma'.

Hello Prof Nolze,

I have a slight different opinion regarding the hardness of additively manufactured samples. AM samples typically have a higher hardness value compared to conventional manufacturing routes due to the presence of higher amounts of dislocation/martensitic phases resulted from fast cooling/solidification rates. However, this comes as a trade-off for the ductility.

For Roshan, probably you might want to double check ur sample's porosity values as suggested by Anton.

Thank you, Mr Sun. I have not done a quantitative analysis on porosity. The sample was manufactured using an Industrial SLM machine and I would expect them to be denser. Also, the region where I have done the hardness does not have any martensite or carbide phases and it was an elongated structure with an approximate width of 350 nm.

I am sure I got you when you suggested to check the sample's porosity values. Is there any experiments to Quantify it or my SEM Image analysis?

Hi Roshan, typically I rely on either Archimedes principal or image analysis (OM images for polished samples will do the job). For the image analysis, ImageJ is able to give a quantitative value if that's what u are looking for. Good luck.