Effect of super-rapid induction quenching on fatigue fracture behavior of spherical graphite cast iron FCD500

Fatigue crack propagation in laser alloyed ductile cast iron surface

“…Some graphite nodules near the interface are surrounded by an intergranular failure facet band (marked by AA 0 at G2 and BB 0 at G4, respectively), which is typical in a martensite fracture fractograph. 2,3,23 This indicates that the graphite nodule in the heat affected zone is surrounded by a martensite shell formed by rapid cooling and carbon diffusion from the graphite nodule. 2,3 The crack initiated at the alloying zone or the heat affected zone is not easy to break through the martensite shell wrapping graphite nodule and rather would propagate through a bypass.…”

“…2,3,23 This indicates that the graphite nodule in the heat affected zone is surrounded by a martensite shell formed by rapid cooling and carbon diffusion from the graphite nodule. 2,3 The crack initiated at the alloying zone or the heat affected zone is not easy to break through the martensite shell wrapping graphite nodule and rather would propagate through a bypass. No cracks are developed outside the martensite shell, which shows that the separation of the graphite nodule from the matrix is restricted by the martensite shell and the fatigue crack propagation is retarded.…”

“…The super-rapid induction quenching, the nitriding, and the laser alloying are among various techniques developed to improve their fatigue resistance through surface modifications with alloy elements or heat treatments. [1][2][3][4][5][6][7] The laser surface alloying (LSA) is considered very effective and economical in this respect, and it improves the fatigue resistance of the surface layer while keeping the substrate materials free from the heat effects. In the LSA process, the high energy of a laser is used to melt a part of the substrate in a small depth, and the precoated or the directly delivered alloy powders are put onto the substrate to be molten and alloyed with the molten metal.…”

Damage mechanism of a nodular cast iron under the very high cycle fatigue regime

“…The high-frequency, high-cycle fatigue of the components can result in essentially unpredictable failures of the working system. In order to investigate the fatigue properties and prime causes of the components failures in very high cycles regime, ultrasonic fatigue test system had been developed and it offers an alternative testing method for generating the data necessary at very long fatigue lives (Bathias and Paris, 2004;Kim and Ji, 2006). High frequency fatigue loading is always related to the thermal dissipation in metals and temperature rising.…”

“…In other words, fatigue damage process is a complicated energy dissipation process. There are several kinds of energy form in the fatigue process; it includes elastic strain energy, plastic strain energy and heat dissipation (Kim and Ji, 2006;Xue et al, 2006a;Luong, 1998;Xue, 2005). High performance materials, which are particularly important for automobile design, are subjected to very high cycles fatigue loading in their working service, under high cycle fatigue conditions, more than 90% of the fatigue life is spent before cracks can be detected.…”