Micromechanical aspects of fatigue crack growth propagation in powder heterogeneous materials such as porous composite nickel-bearing steels are discussed. It is found that the residual porosity of powder steels (usually 3-5%) is favourable to damage initiation under cyclic loading and damage growth due to fatigue crack propagation. High strength austenitic phases of powder composite steel generated by the sintering process because of microscale volumes rich in nickel are formed near nickel powder particles and these microscale austenitic volumes are favourable to fatigue damage growth. The powder nickel-bearing steel microstructure contains ferrite and austenite phases and pores in the iron-carbon-nickel base system. In addition, under cyclic loading, the meta-stable austenite phase is turned into a carbide-ferrite substructure, resulting in a change in the fatigue crack propagation process. Considering that the lifetime of functional materials in friction wearing parts or cutting tools is defined through the crack propagation time, the experimental research into fatigue crack resistance for powder nickel-bearing steels presented in this paper should have substantial practical importance.
Technology, Law and Insurance
Volume 4, 1999 - Issue 3-4
![Sample our Law journals, sign in here to start your FREE access for 14 days]({"type":"image" , "src" : "/sda/5942/TOC-Subject-Sample-2021-Law.jpg"})