Fracture Microindentation on boride layers on AISI 1020 steel

In this paper, an attempt has been made to enhance the fracture toughness (K-c) of boride layer using multi-component (Ni, Cr and B) laser boriding. The fracture toughness of continuously pack borided, interrupted pack borided and multi-component (Ni, Cr and B) laser borided steel specimens was measured using Vickers microindentation fracture toughness test as per ASTM E384 standard. The fracture toughness of continuously pack borided layer was 2.5 - 3.3 MPa.m(1/2). The fracture toughness of interrupted boride layer was in the range of 3.5 - 4.9 MPa.m(1/2). The fracture toughness of multi-component (Ni, Cr and B) laser borided layer was in the range of 13.8 - 18.3 MPa.m(1/2). A significant improvement in fracture toughness of laser treated specimens was observed from the experimental results. This may be due to better distribution of boron, nickel, chromium and other alloying elements due to laser treatment and relatively more uniform boride layer as compared with continuously pack borided layer and interrupted pack borided layer.