M. Kumar, A. Sodhi, S. Pandey, Indian Institute of Technology Delhi, New Delhi, India
Surface modification by weld deposition is used to enhance the service life of a variety of engineering components. In this technique a material is deposited by welding on industrial components to enhance their surface characteristics. Material loss due to wear in many industries can be extremely high, notwithstanding surface hardening heat treatments or protective coatings of wear resistant materials before components are put into service. After a period of service these components will be reduced in size by wear until they can no longer be used and either replacement or rebuilding needs to be considered. Rebuilding of these components to the required size by welding can considerably reduce costs. Weld surfacing is a cost effective and proven method for depositing protective coatings. The effect of weld surfacing on component life and performance will depend upon the surfacing material and the application process.
This paper reports the graphite transfer behaviour during SMAW process using E-6013 and E-7018 type covered electrodes. A 1.5 mm thick graphite coating was made on the active surface of the ploughshare using an inorganic binder. Deposited beads were analyzed for bead geometry and shape relationships, chemical analysis, wear rates, micro-hardness and microstructure.
Chemical analysis revealed that the graphite transfer took place under all conditions of testing. The weight percentage varied from 0.698 to 0.92. Weld deposits made with E-7018 electrodes showed better carbon pickup as compared to E-6013 electrodes. Weaving resulted in higher pickup than straight weld bead.
Weld beads showed higher reinforcement and as low a dilution as 10% in some cases. Hardness tests showed variation form 190-539 VHN. Microstructure analysis had clear evidence of the formation of hard phases in composite metal. Wear rate decreased by 40% after graphite transfer.
Linear Abrasive Wear Rig as per the ASTM standard G132-96 was used.
Summary: The graphite transfer behaviour during SMAW process using E-6013 and E-7018 type covered electrodes was investigated. A 1.5 mm thick graphite coating was made on the active surface of the ploughshare using an inorganic binder. Deposited beads were analyzed for bead geometry and shape relationships, chemical analysis, wear rates, micro-hardness and microstructure.
