Tempered martensite embrittlement of an alloy steel forging from an automobile vehicle system

Abstract

A thorough root cause analysis was conducted on a prematurely failed wedge component used in defense automobiles. It is made of PCrNi3MoVA, a defense grade alloy steel and is designed to operate in high pressure loading conditions up to 540 MPa. The investigation covered various aspects, including operating conditions, visual examination, chemical composition, bulk hardness, microstructure, and mechanical testing. Overall, an industrial approach was used to determine the root cause of failure. Visual inspection revealed that the fracture surface was flat and there were no signs of beach marks. Mechanical testing revealed that the material had lost its impact strength and had induced brittleness in it. Microstructural analysis revealed tempered martensitic structure directing towards the improper tempering of the material since there was a reduction in toughness. Heat treatment cycle was designed and metallurgical examination was done which showed an improvement in impact toughness of the material.