Influence of Ti and Nb addition on the microstructure, mechanical, and machinability properties of 316L stainless steel fabricated by powder metallurgy

Abstract

In this study, titanium and niobium element powders in determined amounts (0.25 and 0.5 wt%) were added into the 316L stainless steel matrix by means of powder metallurgy (PM) technology, either singly or in pairs, and the desired composition was obtained as a powder mixture. The powders used in the study were cold pressed tensile sample molds prepared in ASTM 8 M standards, unidirectionally cold pressed under 700 MPa compression pressure and formed into blocks. After pressing, the raw strength samples were sintered in an atmosphere-controlled tube furnace at 1325 °C for 2 h in an argon atmosphere. The microstructure and mechanical properties of the produced PM steels were characterized by optical microscope, SEM, EDS, and tensile test. The results showed that the stainless-steel samples with 0.25(Ti–Nb) added composition to 316L stainless steel had the highest yield strength and tensile strengths. However, with the addition of 0.5Ti, 0.5Nb, and 0.5(Ti–Nb) to 316L stainless steel, a decrease was observed in the mechanical properties. Moreover, the MQL machining is better on the machining output such as surface roughness and cutting temperature than dry machining in terms of a sustainable machining process.

The Effect of Mn and Ti Ratio on Microstructure and Mechanical and Machinability Properties of 316 L Stainless Steel Used in Biomedical Applications

“…According to the Schaeffler diagram [29] based on Cr and Ni content (austenite stabilizer), the primary phase of the produced material is still austenite. When Figure 7 and Table 4 are examined, it is thought that this increase in tensile strength and hardness occurs through strength increasing mechanisms such as precipitate hardening with the formation of carbide, nitride and carbonitride precipitates on the matrix and refinement of grain size as seen in the microstructure pictures [21]. Moreover, an increase in tensile strength was observed when 0.35 wt % Ti and Mn were added.…”

“…Here, it is considered to be a precipitate of CrSiMoC(N). As a matter of fact, it has been stated in the literature that binary and multiple precipitates are formed in the matrix and grain boundaries [21]. Figure 5 shows the SEM microstructure image taken from Alloy X with 1.5% (Ti + Mn) added.…”

“…There are studies in the literature that demonstrate that the addition of alloying elements increases porosity. For example, Erden et al, in their study, determined that the addition of Mo to unalloyed steel increases the number of pores [21], while the porosity increases with the increase in the weight percentage of the alloying elements. For example, when the two elements (Ti-Mn) were added, the relative porosity increased from 8.06% in Alloy I to which alloying elements the samples (Alloy IV-VII and X) were added 9.11-9.21 and 12.01% in, respectively.…”