Name: PÂMELA MIRANDA CREMONINI
Publication date: 01/11/2024
Examining board:
Name |
Role |
|---|---|
| ANDRE PAULO TSCHIPTSCHIN | Coorientador |
| CHERLIO SCANDIAN | Presidente |
| HENARA LILLIAN COSTA MURRAY | Examinador Externo |
| NATHAN FANTECELLE STREY | Examinador Interno |
Summary: Wear performance of the grate bars used in the transportation of iron ore pellets in pelletizing furnaces was evaluated in this study. The bars, made of high-temperature resistant austenitic stainless steel, are subjected to intense abrasive wear due to contact with the pellets. Metallographic and EDS analyses identified the presence of chromium carbides (Cr23C6) and eutectoid austenite in the material's microstructure, corroborating the results obtained from Thermo-Calc®, which revealed that the phases present after the solution treatment of this steel were liquid, austenite, and MC and Cr23C6 carbides. Linear scratch tests, using standard Rockwell C and synthetic hematite indenters, were conducted to understand the behavior under a single abrasive event. The results showed a plastic response to scratching, with the predominant wear micromechanisms being microplowing and microcutting for both indenters. The diamond indenter produced cavities 16.6% larger and caused greater material displacement compared to the hematite indenter, resulting in morphologically distinct grooves when comparing the two indenters. During the linear scratch test, the coefficient of friction was measured, showing similar values for both indenters (0.15). However, from 3.5 N during the load progression, the coefficient of friction for the hematite indenter increased and surpassed that of the diamond indenter, which remained stable throughout the test. This behavior can be attributed to the possibility of hard stainless steel particles being dislodged and adhering to the hematite indenter, resulting in the observed variation during displacement. For the tribological characterization of ASTM A297-HH (disc), pin-on-disc wear tests were also performed with loads of 4.5 and 12 N. The coefficient of friction obtained in this test was 0.69 for 12 N and 0.67 for 4.5 N. The wear rate was 5.53 × 103 mm³/N·m for the higher applied load and 2.90 × 103 mm³/N·m for the lower load. Vickers microhardness measurements were performed on the wear tracks and revealed a significant increase in hardness on the track, indicating the occurrence of work hardening in the contact region between the hematite ball and the disc. Evaluating the track morphology, it was observed that the worn surface exhibits typical adhesion characteristics, with grooves indicating material transfer between the body and the counterbody.
Keywords: Austenitic stainless steel; Abrasive wear; Grate bar; Pin-on-disc test; Linear scratch test.
