Cracking Failure Analysis of HDR Ultra - Low Carbon Duplex Stainless Steel Forked Joint

Abstract

The HDR ultra - low carbon duplex stainless steel forked joint could crack and fail during wire cutting and machining. In this paper, the causes of the above - mentioned cracking were comprehensively analyzed by means of crack macroscopic morphology analysis, analysis on the fracture of impact test sample, chemical composition analysis of substrate, mechanical property testing of cracked area, metallographic structure analysis, fracture microscopic morphology analysis, micro - area energy spectrum analysis and other items. Results showed that the reason for the cracking of HDR forked joint was that the cooling speed of HDR material was too low in the process of solution heat treatment, so a large number of σ phases precipitated at the grain boundaries in the microstructure. The σ phases were brittle, which made the HDR material suffer a sharp decrease in plasticity and toughness, and then cracked in the process of wire cutting and machining.

Keywords

• hdr ultra - low carbon duplex stainless steel|σ phase|solution heat treatment|failure analysis