The aim of the present investigation is to evaluate the influence of the powder size of Cr3C2-25NiCr spraying powder on the fatigue behavior of HVOF-sprayed coating on the ASTM A516 steel substrate. Conventional commercial Cr3C2-25NiCr spraying powder was previously treated through high-energy milling. The crystallite sizes of milled powders were measured by X-ray diffraction and transmission electronic microscopy. Three different powder formats of the same Cr3C2-25NiCr composite were subjected to HVOF spraying to produce (i) a Milled-Coating (from high-energy milled spray powder), (ii) an Original-Coating (from conventional commercial spray powder), and (iii) a 50%–50% mixture of both (Milled + Original-Coating). The same spraying conditions were adopted for all the assessed cases. The sprayed coatings were investigated through the Knoop hardness test and SEM-EDS analysis. In addition, 3-point bending fatigue tests were conducted at different stress levels up to 107 cycles. The coating morphology and roughness effects on fatigue behavior were analyzed. The Cr3C2-25NiCr milled coating presented a lower fatigue life above the fatigue limit and a higher fatigue limit than other coatings; this outcome could be attributed to its lower surface roughness and finer grain size microstructure.

NiCr metal matrix composite reinforced with Cr3C2 particles can be applied as coating to various pieces of equipment, including those operating under fatigue. In the present study, the nanometric powder was obtained by high energy milling and sprayed by the high velocity oxygen fuel technique on ASTM A516 steel substrate. The comparison was made between the layer obtained from powders in nanometric scale, micrometric scale and mixing 50% of both. The coating thickness, hardness, microstructure, porosity and roughness were evaluated. Fatigue tests were performed on the three coatings in addition to the layer free substrate. The effect of coating morphology and its roughness on fatigue performance was studied. The surface roughness of the Nano coating was significantly lower than both of the other coatings. However, the three different layers that were tested did not experience significant differences in their fatigue performance. All three coatings had lower fatigue performance than the steel substrate. Article Comparative study of the fatigue performance of the micro and nanometric Cr 3 C 2-25NiCr coating sprayed by HVOF on ASTM A516 steel substrate