Crack propagation in a hard-faced AISI type 304 stainless steel

This work presents the results of a study on crack propagation in AISI type 304 stainless steel pipe coated with a wear-resistant (hard-facing) alloy. This layer was applied by electric arc welding directly to the pipe. After the alloy solidifies, cracks are generated. Most of them start at the surface of the hard-facing alloy and grow towards the steel. The objective of this work was to analyze the crack propagation into the stainless steel by means of thermal cycling. For this, four samples were obtained from a pipe. The samples were subjected to 40 thermal cycles. Heating was achieved in an electric resistance furnace up to 700 °C, the samples were held at this temperature for 5 min and were cool down outside the furnace to 300 °C. Three samples were cooled in air and the last one in water. One of the samples underwent an aging treatment for 168 h at 750 °C previous to the cycling. All the samples were metallographically inspected before and after thermal cycling by light optical microscopy. Microhardness testing was carried out on all the samples.