EFFECT OF PREHEAT ON THE MICROSTRUCTURE AND HARDNNES OF THE SURFACING OF SHREDDER HAMMERS WITH AWS E FeCr-A1 ELECTRODES

Abstract

Introduction:
The AWS E FeCr-A1 electrode does not guarantee deposits in a single layer that can counteract the wear of the shredder hammers. Microstructure in the first layer is primary austenite (ɣ- Fe) and an interdendritic eutectic network (austenite and carbide). The hardness is 50 HRC.
Objective:
To evaluate the preheat effect on the hardness and microstructure of deposits obtained with the AWS E FeCr-A1 electrode.
Materials and Methods:
The deposits were obtained on S275JR steel plates, using single and double layer of recharge at room temperature and at 200°C, with shielded metal arc welding (SMAW). The samples were trimmed, polished and etched with Murakami reagent. The
microestructure was observed by optical microscope (OM). The Vickers microhardness was determined using a Shimatsu microdurometer.
Results and Discussion:
Microstructure of deposits obtained at room temperature using simple and double layer consist of primary grain of austenite (ɣ- Fe) and eutectic (ɣ- Fe and M7C3). The highest hardness was obtained in the sample with double layer (723 HV). Microstructure of deposit performed at 200°C is composed by large amount of austenite (ɣ- Fe) and lower fraction of eutectic (ɣ- Fe and M7C3).
Conclusions:
With a temperature increase (200°C), predominant microstructure is austenite (ɣ- Fe), and deposit reaches only a hardness of 572 HV, below that indicated for the consumable AWS EFeCr-A1 which is 650 HV.