流動層によるオーステナイト系ステンレス（ＳＵＳ３０４）鋼のほう化処理

Abstract

Boronizing is well known to improve wear and corrosion resistance, because boron forms intermetallic compounds. Although the characteristics of boronized austenitic stainless steel have been reported, little information is available on boronizing in fluidized beds. We analyzed, the boronized layer using glow discharge emission spectrometry (GDS), X-ray thin diffraction, and ESCA. We studied the friction and wear characteristics and corrosion behavior of boronized SUS 304 stainless steel, and obtained the following results, (1) The Knoop hardness was 1900HK for specimen treated for 4h at 1123K. A boronized layer was formed with three lamellar layers, the first layer mainly FeB, the second Fe2B, and the third a ferritic phase. The FeB layer had a fine structure and the physical etching of GDS was useful for observing this microstructure.(2) The boron concentration was about 50 at% in the first layer, about 40 at% in the second, and about 30 at% in the third. The boronized layer contained about 10 at% Cr. Ni and Si enrichment were detected in the ferritic phase.(3) The boronized specimen had a high wear resistance to SUJ 2 and Al2O3 than an untreated one, but the friction characteristics was not greatly improved.(4) Corrosion resistance was improved against 0.1N HCl but not against 0.1N H2SO4 or 10% oxalic acid solution.