Influence of hot rolling and heat treatment on structure and properties of HSLA steel explosively clad with austenitic stainless steel

The present work aims at studying structure-property correlations in an explosively clad HSLA steel with austenitic stainless steel of AISI 304L grade. The clad plate was subjected to hot rolling followed by a quenching and tempering treatment to achieve better mechanical properties in the base plate. Optical microscopy studies revealed that the interface between the two steels was wavy in the as clad plate and the waviness decreased substantially due to hot rolling. Subsequent heat treatment has not shown any significant effect either. The base plate had tempered martensite/bainite structure in as clad or heat treated conditions and ferrite-pearlite-bainite structure in hot rolled condition. The grains were finer and elongated near the interface. The stainless steel exhibited equiaxed grain structure in as clad, hot rolled or heat treated plates. Tensile properties and charpy impact energy of the base plate were lowered due to hot rolling and then increased substantially due to heat treatment. The microhardness was observed to be a maximum at the bond interface for all three conditions studied. The shear bond strength was the highest in the as clad condition and decreased for the rolled as well as heat treated conditions. Scanning electron microscopy fractography on shear bond specimens revealed the presence of predominantly equiaxed dimples with few regions of rubbed fracture. Quantitative electron probe microanalysis across the bond interface indicated linear change in concentrations of nickel, chromium and manganese between the levels appropriate to the clad layer and base metal.