Cathodoluminescence analysis of nonmetallic inclusions of nitrides in steel

Abstract

Identification of nitride inclusions such as boron nitride (BN) and aluminum nitride (AlN) is important in the steelmaking industry because BN inclusions deteriorate the creep strength of ferritic heat‐resistant steel, and AlN inclusions cause transverse cracking in twin‐induced‐plasticity steel. The conventional method employed for the analysis of such inclusions in steel comprises both optical microscopy and electron probe microanalysis (EPMA), which is the time‐consuming. The aim of this study is to investigate the application of cathodoluminescence (CL) analysis (both images and spectra) to the rapid identification of BN and AlN inclusions. Measurement samples were prepared by heating mixtures of 99 mass% Fe and 1 mass% B or Al powders at 1550°C in a nitrogen atmosphere. BN inclusions larger than 5 μm and AlN inclusions 20 μm in size were identified within 1 second on the basis of their luminescence color (blue‐violet for BN and blue for AlN) in the CL images. We demonstrated that BN, AlN, and alumina inclusions could be identified from their CL spectra without the conventional method of EPMA. Capturing a CL image can provide a means of rapidly identifying BN and AlN inclusions in steel. We also carried out CL analysis on a sample containing TiN inclusions which can trigger cleavage fracture in low‐carbon steels. No luminescence was detected in the CL image, and there were no CL spectral peaks, indicating that it is difficult to apply CL analysis to the identification of TiN inclusions.

Effect of Reheating and Quenching on the Cathodoluminescence Intensity of Free Lime in Steelmaking Slag

“…The acceleration voltage of the STEM was set to 200 kV. The CL images and spectra were acquired using a custom SEM-CL system, whose details have been previously reported (Imashuku et al, 2017a(Imashuku et al, , 2017b(Imashuku et al, , 2017cImashuku & Wagatsuma, 2018, 2019a, 2019b, 2019c, 2020c, 2020dTsuneda et al, 2019). In brief, the CL images were captured through a quartz viewport attached to the SEM (Mighty-8DXL, TECHNEX, Tokyo, Japan) by a digital mirrorless camera (α7RII, Sony Corp., Tokyo, Japan) equipped with a zoom lens (LZH-10A-05T, Seimitu Wave Inc., Kyoto, Japan).…”

Simple identification of Al2O3 and MgO·Al2O3 spinel inclusions in steel using X‐ray‐excited optical luminescence

“…We also acquired CL spectra of inclusions in the model steel sample using a custom SEM ‐ CL system. Details of the SEM ‐ CL system are reported in our previous papers . The measurement duration for the CL spectra was 100 s.…”

“…Details of the SEM-CL system are reported in our previous papers. [17][18][19][20] The measurement duration for the CL spectra was 100 s. Figure 2. Inclusions emitting blue, red, and green luminescences were detected in the XEOL image.…”

Identification of MgO·Al2O3 Spinel on MgO Refractory for Aluminum Deoxidation Process of Stainless Steel Using Cathodoluminescence and X-ray Excited Optical Luminescence Imaging

“…The SEM-CL system has been described in detail in our previous papers. [28][29][30][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48] In brief, the CL images were captured using a digital mirrorless camera (a7RII, Sony Corp., Tokyo, Japan) equipped with a zoom lens (LZH-10A-05T, Seimitu Wave Inc., Kyoto, Japan) via a quartz viewport attached to a SEM (Mighty-8DXL, TECHNEX, Tokyo, Japan). The detectable wavelength range of the camera was from 420 to 680 nm.…”