Experimental and numerical evaluation of multi-pass scratch on borided ARMCO iron

Abstract

Thermochemical treatments are used for increasing the surface mechanical properties of iron and steels. The wear on mechanical components caused by sliding contact is an important parameter in the field of tribology. In this study, the wear resistance of ARMCO pure iron hardened by the powder-pack boriding process was evaluated using unidirectional dry sliding. The thermochemical treatment of boriding was carried out at temperatures of 850 °C for 1, 2 and 3 h of exposure time. Surface properties such as hardness and Young's modulus were obtained using the nanoindentation technique. The wear testing was performed by multi-pass scratch using an Al2O3 sphere as counterpart, constant loads of 20 and 30 N and 50, 100 and 150 passes (with a sliding distance of 5 mm for each pass). The Archard's model was used to obtain the wear coefficient for each treatment condition. The finite element method applying mesh nonlinear adaptivity was used to evaluate the stress field in the borided samples under sliding contact. Results showed that borided ARMCO pure iron under unidirectional sliding loading caused both adhesive and abrasive wear. Furthermore, for the boriding conditions established in this work, the wear behavior at loads ≥30 N was governed by both the mechanical properties of the boride layer and its thickness, whereas at lower loads only the mechanical properties of the boride layer influenced the wear resistance.