Influence of heat treatments on the abrasive wear resistance of supermartensitic stainless steel.
Gustavo Borges Coelho1; Washington Martins da Silva Júnior1; Sérgio Souto Maior TAvares2; José Lúcio Gonçalves Júnior1
1 Universidade Federal de Uberlândia; 2 Universidade Federal Fluminense
Resumo
Martensitic and supermartensitic stainless steels are corrosion resistant materials with broad application in chemical, petrochemical and power generation industrial sectors. The supermartensitic stainless steel 13 %Cr (composition: 0.0278 %C; 12.21 %Cr; 5.8 %Ni; 1.95 %Mo; 0.519 %Mn; 0.28 %Ti; 0.0112 %P; 0.0019 %S; 0.013 %N in wt%) is indicated for applications that require corrosive and abrasive wear resistance due to its higher mechanical resistance and hardness in comparison to other stainless steels. In this work the abrasive wear resistance of supermartensitic stainless steel was characterised using pin on disc abrasion tests complemented by pendular scratch tests. The microstructure and mechanical response of supermartensitic stainless steel was modified by five different heat treatments: 1) quenching from 1000°C; 2) quenching and tempering at 300°C, 1 h; 3) quenching and tempering at 500°C, 1 h; 4) quenching and tempering at 650°C, 1 h; 5) quenching and double tempering at 670°C, 2 h followed by 600°C, 2 h. Tempering treatments at 300°C and 500°C promoted a hardening effect on the steel due to fine Mo2C precipitation. Tempering at 650°C and double tempering caused softening of the material due to the large amount of austenite as observed by magnetic measurements and metallographic analysis. The abrasive wear resistance was obtained using pin abrasion tests. In this apparatus, the pin sample slides against sandpaper making a spiral trajectory of 4,2 mm. Corundum (Al2O3) 220 mesh sandpaper was used. The normal load of 13.5 N was applied directly by means of dead weight. Results showed that the average abrasive wear resistance increased up to 6 % for samples tempered at 650°C in comparison with the non-tempered material due to the presence of Mo2C precipitates. For double tempered samples, the wear resistance decreased 8.5 % due to their higher amount of austenite. Pendular scratch tests helped to understand the change in wear rate obtained by pin abrasion tests.
Palavras-chave: abrasive wear; ; supermartensitic stainless steel; pin abrasion test; pendular scratch test; wear mechanism