Effect of some of the high-melting compounds on the properties of a weld-on alloy

Summary

• 1. The structure of an alloy consisting of a mixture of coarse- and fine-grain carbides and borides arranged as isolated inclusions in the base metal imparts high strength and wear resistance to the weldedon layer, thus confirming the possibility of direct high-grade alloying of the welded-on layer with highmelting compounds.

• 2. The main reason for the tendency of a wear-resistant welded-on alloy to form hot cracks is a lack of eutectic. Maximum tendency to hot cracking is shown by alloys with a structure of austenite and carbide eutectic in the form of thin layers in interaxial spaces between columnar crystals. Hence, when alloying the welded-on layer with borides, an increase in the latter's concentration helps to refine the primary structure and to eliminate hot cracks.

• 3. The optimal composition of the alloy is formed by alloying with a mixture of 10% TiB₂+90% B₄C (10–15%) with the following chemical composition: 0.83–0.97% C, 2.9–4.2% B, 0.07–0.09% Ti, with an electrode coating thickness per side of 1.0–1.1 mm.

• 4. The structure of alloys coatings applied with electrode of TBK type shows high microhardness in the component phases, which fact gives the alloy high over-all hardness and heat resistance.

The manufacture of powder wire (ribbon) with a boride base is an important reserve for reducing the cost of surfacing materials.