A comparative study of mechanical and tribological properties of AISI-304 and AISI-316 submitted to glow discharge nitriding

Abstract

cannot be applied. The mechanical response for external loads is then better simulated by instrumented indentation performed on ion beam modified surfaces rather than on cross-sections.In the present work we report a comparative study about structural, mechanical and tribological properties of AISI 304 and AISI 316 stainless steels submitted to nitrogen glow discharge at different substrate temperatures from 300 to 500 °C. Structural characterization was evaluated by X ray diffraction (Bragg-Brentano geometry) using Rietveld refinement. Hardness, elastic modulus profiles and surface topography were obtained by instrumented indentation. Conventional Vickers measurements were also employed in order to obtain deeper hardness profiles. Tribological and wear behavior were studied by reciprocating sliding tests. Experimental ProcedureCommercial sheets of AISI 304 (Ni 8.63%, Cr 16.04%, C 0.047%, Si 0.48%, Mn 1.37%, S 0.005%, Mo 0.09%, P 0.029% weight, with Fe being the balance) and commercial rods of AISI 316 (Ni 11.64%, Cr 15.68%, C 0.10%, Si 0.34%, Mn 1.73%, S 0.031%, Mo 1.86%, P 0.029% weight with Fe being the balance) were cut in 1.5 x 1.5 x 0.5 cm and φ = 3 cm and 0.5 cm thick pieces, respectively. The samples were mechanically polished up to ¼ µm diamond paste in order to obtain a final mirror finish.DC glow discharge was performed in N 2 :H 2 -20:80 atmosphere at 600 Pa with prior H 2 sputtering at 100 °C during 2 hours. The plasma current ranged from 200 to 300 mA, resulting in sample ensembles with substrate temperatures of 300, 400 and 500 °C. The temperature was controlled by monitoring a backside thermocouple and adjusting the plasma current as needed. All samples were nitrided during four hours. Mechanical and tribological properties of AISI 304 and AISI 316 stainless steels submitted to glow discharge ion nitriding are reported. The atmosphere was 20:80 -N 2 :H 2 with substrate temperatures ranging from 300 to 500 °C. Treatment at 300 °C produced expanded austenite (γ N ) in both steels. Increasing the temperature, the phases γ′-Fe 4 N and ε-Fe 2+x N were present and the latter is the major phase for AISI 304. At 500 °C, the CrN phase was also identified in both steels. Hardnesses of about 13-14 GPa at near surface regions were obtained in both steels. Moreover, AISI 316 nitrided at 500 °C has the deepest hard layer. Tribological tests showed that wear can be reduced by up to a factor of six after the nitriding processes, even for a working temperature of 300 °C. The profiles during and after nanoscratch tests did not reveal significant differences after nitriding processes in both steels.

Temperature-dependent determination of electron heat capacity and electron-phonon coupling factor forFe0.72Cr0.18Ni0.1

“…For Fe 0.72 Cr 0.18 Ni 0.1 we used a face centered cubic (fcc) crystal structure with a lattice parameter of 3.59Å 19 whereas for Fe in the fcc structure we used 3.52Å 20 . The convergence of the self-consistent potentials have been carefully checked with a number of 834 kpoints in the irreducible part of the Brillouin zone.…”

Martensitic Stainless Steels Low-temperature Nitriding: Dependence of Substrate Composition

“…For this purpose, lowtemperature plasma-assisted techniques is among of the most studied techniques for this steel class. If processing parameters are conveniently chosen, it is possible to obtain a treated surface presenting higher hardness and corrosion resistance than the untreated surface [7][8][9][10][11][12][13][14] . However, if the process parameters are not correctly selected, the treated surface can present a corrosion resistance lower than that expected for the bulk material after adequate solution treatment, which must be strongly avoided particularly on the case of stainless steels.…”

Behavior of nitrided and carburized AISI 904 L stainless steels under severe light ion beam irradiation with plasma focus

“…and Baldenebro‐López et al . According to Nascimento et al . in their analysis of the two important stainless steels in industry, AISI 316 grade has a parameter lattice of 3.5935 Å, and AISI 304 steel has a value of 3.5918 Å.…”

“…For comparative purposes, the lattice parameter of the base material was measured using the GIXRD technique: AISI 904 L had a constant of 3.6009 Å. The higher Ni concentration in AISI 904 L steels develops higher lattice parameters in comparison with the AISI 300 series, for example, in the works of García Molleja et al [11] and Baldenebro-López et al [28] According to Nascimento et al [29] in their analysis of the two important stainless steels in industry, AISI 316 grade has a parameter lattice of 3.5935 Å, and AISI 304 steel has a value of 3.5918 Å.…”