(Ti, Ca)-oxide in 409L stainless steel

(Ti, Ca)-oxide in 409L stainless steel

Figure 1: SEM images of pitted inclusions in 409L AOD alloy after potentiodynamic test in 0.5 M NaCl solution and its potentiodynamic curve. Scale bar: 2 µm.

Inclusion name: (Ti, Ca)-oxide
Record No.: 864
Inclusion formula: No data
Inclusion type (Macro/Micro/Nano): Micro
Inclusion type (Exogenous/Indigenous): Indigenous
Inclusion classification: Oxide
Inclusion composition in weight %: No data
Sample: 409L stainless steel
Steel composition in weight %: No data
Note: It is well documented that manganese sulfides (MnS) among non-metallic inclusions act as initiation sites for pitting corrosion in commercial stainless steels. However, independent effects of other non-metallic inclusions such as oxide and nitride on localized corrosion in stainless steel have hardly investigated because of the low lateral resolution of the standard electrochemical experiment methods. Traditional macroscopic electrochemical behavior is simply the sum of the contributions of the different grains or phases, multiplied by their individual degree of coverage. A new electrochemical device, the capillary-based microdroplet cell gives facilities for micro-electrochemical investigations at high resolution.
It was found from the micro-probe technique using a micro droplet cell that pitting corrosion initiated at the interface between round (Ti, Ca)-oxide and matrix (Fig. 1). On the other and, Ti-nitrides in VOD alloy were inactive to pitting corrosion. For 409 alloy refined by AOD, the resistance to pitting corrosion increased linearly with Ti content in the (Ti, Ca)-oxide, but decreased with Ca content in the (Ti, Ca)-oxide.
Reference: Not shown in this demo version.