The Effect of Heat Treatment on the Performance of Antiwear Steel Coatings Deposited on AISI 1015 Steel Substrates

Abstract

The critical components of mining equipment generally work in relative motion and in an abrasive environment. Under these circumstances, wear by friction represents the largest portion of the cost associated with failure and maintenance of sliding bearings. Thus, antiwear coatings are extensively applied aimed at returning such equipment to its initial condition. Tamping machines are a typical type of equipment working in this condition and the focus of the present research work, whose goal is to investigate the performance of conjugates made of an MnSi low-alloy steel coating deposited on an AISI 1015 low-carbon steel substrate and subjected to three distinct heat treatment routes (normalizing and deep and surface hardening). Coating deposition was performed using gas metal arc welding. The performance assessment is based on microhardness and residual stress distributions, friction coefficient, wear mechanisms, and wear rate. The results indicate that ferritic and pearlitic microstructures were obtained after normalizing, whereas deep and surface hardening produced lath martensite. Consequently, the value of surface microhardness of the coating was 176 HV after normalizing, 356 HV after deep hardening, and 466 HV after surface hardening. Normalizing induced shallower compressive residual stresses of lower intensity, whereas surface hardening induced compressive residual stresses of higher intensity to reach deeper beneath the coating surface. More refined grains (martensite laths) were associated with higher microhardness values and compressive residual stresses of higher intensity, thus suggesting that this condition leads to higher wear resistance. The normalized conjugate presented the lowest friction coefficient and the highest wear rate, and the hardened coatings presented similar behaviors with regard to wear resistance.

Keywords:

• Steel coating
• heat treatment
• tamping machine
• friction
• wear

Acknowledgements

The authors thank SuperMETAL (Governador Valadares-MG, Brazil) for the provision of the coatings and both the Pontifical University of Minas Gerais (PUC Minas, Brazil) and the Center for the Development of Nuclear Technology (CNEN-CDTN, Brazil) for the provision of laboratory facilities.

Additional information

Funding

This study was partly financed by the following Brazilian research agencies: Coordination of Superior Level Staff Improvement (CAPES, finance code 001), National Council for Scientific and Technological Development (CNPq), and Foundation for Research of the State of Minas Gerais (FAPEMIG). The research data provided are my co-authorship.