Introduction to an impact fatigue testing method in order to assess the properties of different steel grades with various applied surface treatments

Abstract: During this project, several different steel grades that were made by Ovako
steel company were chosen, then they were treated differently (Annealed,
through hardened, carburized, nitridized, induction hardened, and DLC
coated), finally by the means of an in house Vibrophore machine, and a
costume made cyclic impactor a test setup were introduced.
Samples were tested in two different force conditions of 1900N and 2400N,
and in four different impact cycles as per 1000, 10000, 100000, 500000,
then surfaces of these specimens were analyzed both macroscopically and
microscopically and achieved results were documented.
Finally a comparison among the size of the biggest appeared surface ring
cracks, number of appeared surface ring cracks that were above 40µm,
indentation radius and penetration depth of the impacted surface areas
after applying cyclic impact force were made, and results were shown.
As the final result of the introduced impact fatigue test it is concluded
that samples designated as I and H (Ovako steel grade 804Q_DLC coated,
528Q_DLC respectively) had the same and best impact fatigue resistance
among the tested samples, following by DLC coated samples designated as G
(803J), these samples were followed from the best to worst as per samples E
(528Q_induction hardened), samples B (256G_carburized), samples J
(804Q_through hardened), samples D (277Q_nitrided), samples C
(225A_nitrided), and worst achieved results were from samples designated as
A (804Q_annealed).