Fatigue Test of Coated Mild Steel with Nickel and Aluminum

Abstract

In this research, we try to study the fatigue resistance of coated mild steel 1020 AISI. The alloy was coated with Al in single process using pack cementation technique and Ni using electrodeposition technique. Both processes were also used for coating the same alloy (double layer coating). The fatigue resistance of these coating was compared with the base alloy and with those subjected to a heat treatment at the same conditions of time and temperature. The aim of this study was to understand the effect of the temperature and coating type on the fatigue life. The results obtained, based on XRD, Fatigue test, optical microstructure and hardness measurement, that the temperature of heat treatment played the major rule of fatigue life reduction. This can be attributed to the phase transformation of α­ ferrite steel to pearlite ( ferrite + cementite). The results also showed that the coating types have a very important effect on fatigue life. The coatings performed at high temperature (aluminizing) revealed a negative effect on the fatigue life. This is due to the formation of a new brittle and less ductility of Fe-Al phase on the alloy surface. The electrodeposition of Ni leads to a positive effect which is due to an improvement in surface conditions of the alloys via filling the voids or other defects which are present at the surface. The double layer coating (Ni-Al) applied to some specimens shows some improvement in fatigue resistance, in comparison with a single aluminized specimen. This was attributed to the formation of multiphase layer consisting of Fe-Al and Ni-Al intermetallic compound.