Effect of Sintering Temperature and Atmosphere on Nonlubricated Sliding Wear of Nano-Yttria-Dispersed and Yttria-Free Duplex and Ferritic Stainless Steel Fabricated by Powder Metallurgy

The nonlubricated sliding wear behavior of nano-yttria-dispersed and yttria-free duplex and ferritic stainless steel against a diamond tip was studied. The stainless steel samples were fabricated by a conventional powder metallurgy route in which nano-yttria-dispersed and yttria-free duplex and ferritic stainless steel powders were cold compacted and then conventionally sintered at either 1000, 1200, or 1400°C in an argon atmosphere. For comparison, another set of samples was sintered at 1000°C in a nitrogen atmosphere. The wear behavior of sintered stainless steel samples against a diamond indenter was investigated using a pin-on-disc apparatus at 10 and 20 N loads and at a constant speed of 0.0041 m/s. It is proposed that yttria-dispersed stainless steels showed higher wear resistance compared to yttria-free stainless steel due to their improved hardness and density. Stainless steel sintered in a nitrogen atmosphere exhibited better wear resistance than those sintered in an argon atmosphere due to the formation of hard and brittle Cr₂N. The wear mechanisms of stainless steels against diamond were found to be mainly abrasive and oxidative. Semiquantitative analysis of the worn surfaces and wear debris confirmed the occurrence of oxidation processes during wear.