Correlation of Microstructure with Hardness, Wear Resistance, and Corrosion Resistance of Powder-Injection-Molded Specimens of Fe-Alloy Powders

Abstract

In this study, the powder injection molding (PIM) process was applied to Fe-alloy powders. Microstructure, hardness, wear resistance, and corrosion resistance of the PIM specimens were analyzed and compared with those of a conventional stainless steel, SS316L. When Fe-alloy powders were injection molded and then sintered at 1200°C or 1250°C, completely densified specimens with almost no pores were obtained. They contained 63 to 80 vol pct of hard (Cr,Fe) 2 B dispersed in the austenite or martensite matrix. Since these (Cr,Fe) 2 B borides were very hard, thermally stable, and corrosion resistant, hardness, high-temperature hardness, wear resistance, and corrosion resistance of the PIM specimens of Fe-alloy powders were 2 to 5 times as high as those of the stainless steel. Such property improvement suggested new applicability of the PIM products of Fe-alloy powders to structures and parts requiring excellent mechanical properties.

Tribology of a Fe–Cr–B-Based Alloy Coating Fabricated by a Controlled Short-Circuit MIG Welding Process

“…The bulk hardness of M3 specimen was decreased because of the weld dilution that reduced the B concentration and hence reduced the boride particles volume fraction ( Table 2). This finding is consistent with previous studies [2,3,29], which have shown that as the B content increases, the fraction of the hard boride phase increases and consequently the bulk hardness increases. It should be noted that the hardness of the boride particles did not change with the heat input variation.…”

“…It is hence concluded that the dark-contrast particles (b and b 0 ) correspond to boride of Cr and Fe phase of the type M 2 B and the light-contrast matrix corresponds to a BCC solid solution of Fe, Cr, Mn, and Si. For similar Fe-Cr-B-based alloys, it has been reported the boride phase particles as (Cr,Fe) 2 B [2,3]. The formation of the BCC solid solution phase is also consistent with the reported results [2,5,6,[9][10][11]14].…”

“…Wear protection can be provided by metal matrix composites (MMCs), which are multiphase materials composed of hard reinforcing particles embedded in a metallic matrix [1]. One of these systems is the Fe-Cr-B-based alloys that contain hard boride particles, namely (Cr,Fe) 2 B, (Cr,Fe) x B, Cr 2 B, Fe 1.1 Cr 0.9 B 0.9 , and/or Cr 1.65 Fe 0.35 B 0.96 , dispersed in a Fe-based solid solution matrix [2][3][4][5][6][7][8][9][10][11][12][13][14][15]. This system has been shown to exhibit excellent resistance against sliding and abrasive wear [6,7].…”

Effects of (Cr,Fe)2B borides on hardness in powder-injection-molded product fabricated with Fe-based alloy powders

“…Since these cast rods were not sufficiently homogenized, they were held at 1200 1C for 30 min and then cooled in a vacuum furnace. This heat-treatment condition was same to the sintering condition of the PIM process [16].…”

“…For example, conventional stainless steel powders used for the PIM include STS 304L, 316L, 430, and 630 powders [12][13][14][15]. Recently, PIM parts were fabricated with hard Fe-based alloy powders (composition; Fe-43Cr-5.6B-1.8Si-0.2S-0.17C (wt%)) which is called as Armacor TM 'M' (commercial brand name of the Liquidmetal Technologies, Lake Forest, CA, USA) [16]. These parts showed much higher hardness, corrosion resistance, and wear resistance than those fabricated with conventional stainless steel powders.…”