Improving the surface properties of additive-manufactured Inconel 625 by plasma nitriding

Danijela Anica Skobir Balantič (Author), Črtomir Donik (Author), Bojan Podgornik (Author), Aleksandra Kocijan (Author), Matjaž Godec (Author)

Abstract

As a surface-hardening technique, plasma nitriding is a common procedure for improving the properties of conventional Ni-based alloys. The diffusion of nitrogen hardens a layer on the surface of the alloy, leading to better wear resistance and a higher coefficient of friction, as well as a higher surface hardness. This study reports the effect of plasma nitriding on additive-manufactured (AM) Inconel 625 (IN625) compared to its conventional manufactured and nitrided counterparts. The samples produced with the laser powder-bed fusion (LPBF) process were subsequently plasma nitrided in the as-built condition, stress-relief annealed at 870 °C and solution treated at 1050 °C. The plasma nitridings were carried out at 430 °C and 500 °C for 15 h. The growth kinetics of the nitride layer of the AM samples depends on the prior heat treatments and is faster in the as-built state due to the specific cellular structure. The lower nitriding temperature leads to the formation of expanded austenite in the nitride layer, while at the higher nitriding temperature, the expanded austenite decomposes and CrN precipitation occurs. The XRD and SEM analyses confirmed the presence of two layers: the surface layer and the diffusion layer beneath. The lower nitriding temperature caused the formation of expanded austenite or a combination of expanded austenite and CrN. The higher nitriding temperature led to the decomposition of the expanded austenite and to the formation/precipitation of CrN. The higher nitriding temperature also decreased the corrosion resistance slightly due to the increased number of precipitated Cr-nitrides. On the other hand, the wear resistance was significantly improved after plasma nitriding and was much less influenced by the nitriding temperature.

Keywords

additive manufacturing;powder-bed fusion;plasma nitriding;expanded austenite;wear and corrosion resistance;Ni-based alloy;

Data

Language:	English
Year of publishing:	2023
Typology:	1.01 - Original Scientific Article
Organization:	IMT - Institute of Metals and Technology
Publisher:	Elsevier
UDC:	621.8:539
COBISS:	133032451
ISSN:	0257-8972
Views:	14
Downloads:	5
Average score:	0 (0 votes)
Metadata:

Other data

Pages:	str. 1-11
Volume:	ǂVol. ǂ452
Issue:	ǂ[article no.] ǂ129130
Chronology:	Jan. 2023
DOI:	10.1016/j.surfcoat.2022.129130
ID:	22754337