Effect of Hard Coatings on Surface Gray Iron on Fracture Toughness

Abstract

The characterization and fracture toughness with hard coatings formed at the surface of gray cast irons class 30 is evaluated in the present study. The formation of hard coatings was obtained out means of the pack boriding process; the treatment was carried out at temperatures of 1173 and 1223 K during 6 hours. The layers were evaluated by the techniques of X-ray diffraction (XRD), energy dispersive spectrometry (EDS) and microindentation across the thickness of the iron boride layer. Three-point bending tests are carried out to examine the fracture toughness of gray cast irons boriding according to the ASTM 399 standard. Consequently, the stress intensity factor was evaluated by means of the finite element method (FEM) using the package ANSYS 11. 0 creating a two-dimensional model with elements of singularity around the tip crack. The results were compared with the experiments and have been found to be in good correlation.

Mechanical Behavior on Cr Base Steels Surface Treatment

“…Moreover, the nanohardness of the hard coating depends on the presence of residual stress brought about by thermal growth of the iron hard coatings [8][9][10][11] and are factors to consider for the difference of nanohardness values obtained. Also, the static load on Cr steel samples increases as a consequence of the presence of the hard coating, this is according to work [12] evaluating the effect of the hard coating where the fracture toughness depends on the thickness of the hard coatings. The fracture surface of the sample tested with a surface treatment at the condition of 8 h in Fig.…”