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High-purity bearing steel powders were prepared by electrode induction melting gas atomization (EIGA) and plasma rotating electrode atomization (PREP), respectively. The particle size distribution, nitrogen and oxygen content, and microstructure of the two high-purity bearing steel powders were analyzed and compared by laser particle size analyzer, oxygen nitrogen analyzer, and scanning electron microscope. The results show that both of the powders are mainly spherical with the PREP powders (M62-PREP) having the higher sphericity, while the EIGA powders (M62-EIGA) has the higher proportion of satellite powders and irregular powders. The median particle size (D50) of the M62-PREP powders is 108.11 μm, significantly higher than that of M62-EIGA powders (D50=38.68 μm). The composition of the two powders is evenly distributed, there is no obvious element segregation, and the M62-EIGA powders are finer. Both of the powders have the good flowability. The N content (mass fraction) of the pre-alloy electrode rods, M62-PREP powders, and M62-EIGA powders are 0.0070%, 0.0072%, and 0.0068%, respectively. The content of N element does not change much. The O content (mass fraction) of M62-PREP powders increases from 0.0008% of the pre-alloy electrode rods to 0.0035%, while the O content of M62-EIGA powders increases to 0.0089%, indicating the significant increase in the O content. The M62-EIGA powder bearing steels after hot isostatic pressing and sintering have the more oxygen containing inclusions, and the M62-PREP powder bearing steels should have the better performance.

S590 powder metallurgy high speed steels (S590 HSS) were prepared by plasma rotating electrode atomization and hot isostatic pressing. The S590 HSS samples were quenched at 1050, 1100, 1150, and 1180 ℃, respectively, followed by the tempering at 550 ℃ for 1 h (once), −196 ℃ cryogenic treatment for 4 h (once), and tempering at 550 ℃ for 1 h (twice). The effect of quenching temperature on the microstructure and mechanical properties of S590 HSS was studied. The results show that, the microstructure of S590 HSS after the heat treatments mainly consists of martensite, M6C carbides, and MC carbides. With the increase of quenching temperature, the carbides gradually dissolve into the matrix, the carbide content decreases, and the matrix grain size increases. The hardness and compressive strength of S590 HSS increase with the increase of quenching temperature. After quenching at 1180 ℃ and the subsequent heat treatments, the hardness of S590 HSS is up to HRC 67.8, and the compressive strength is 3827 MPa. With the increase of quenching temperature, the bending strength first increases and then decreases, and the impact toughness decreases. The bending strength of the samples quenched at 1100 ℃ reaches the highest as 5473 MPa. The impact toughness of the samples quenched at 1050 ℃ reaches the highest as 76.9 J·cm−2. Considering the microstructure and mechanical properties, the optimum quenching temperature of S590 HSS is 1100 ℃.