Aa. Rakitsky et al., FATIGUE RESISTANCE OF A MEDIUM-CARBON STEEL WITH A WEAR-RESISTANT THERMAL SPRAY COATING, Fatigue & fracture of engineering materials & structures, 17(5), 1994, pp. 563-570
The fatigue behaviour of a Ni-Cr-base powder flame-spray coating on a
0.4% C steel is investigated. Fatigue tests were carried out using mil
d hour-glass profile specimens. Cracks were detected and measured usin
g plastic replicas and an image analysis system. Coated specimens show
ed a slightly lower fatigue endurance than plain specimens under torsi
on loading, while the opposite was observed for push-pull loading. Mic
rocracks in coated specimens invariably form at pores. Contrary to the
usual case of stage I shear growth for a plain 0.4% C steel in tensio
n or torsion loading, the coated specimens show initial crack growth f
rom pores along directions perpendicular to the maximum tensile stress
. The crucial behaviour of short cracks, and their growth rates, relat
ive to the thickness of the coating, are discussed in some detail.