It was proposed in [1–4] to use highly sensitive magnetic and electromagnetic methods to test the abrasion
resistance of quenched and tempered low-alloy and plain high-carbon (0.63–1.00 mass %) steels. The
possibility of assessing changes in the abrasion resistance of martensite structures during tempering was
studied. Therefore, the steels that contained over 10 vol % of residual martensite after quenching were additionally
cooled in liquid nitrogen. As a result, the amount of austenite did not exceed 5–10 vol % in any of
the studied materials. It is of interest to consider the effect of a more significant content of the
γ
phase on
the sensitivity of the coercive-force and eddy-current methods used to assess abrasion resistance of steel
items.
In this study, these effects were investigated in ball-bearing steel
òï15
where, depending on the mode
of bulk quenching, the amount of austenite was as large as 10–45 vol %. Laser quenching is an efficient
method for hardening ball-bearing steel and improving its abrasion resistance [5–8]. In contrast to standard
furnace quenching, where uniform structures emerge either throughout an item or in the majority of the volume
of the item, laser processing creates nonuniform surface layers. It was shown in [9] that the eddy-current
technique may be potentially used to assess the depth of a laser-hardened layer on the surface of steel
òï15
.
In this study, in order to develop an eddy-current technique for testing abrasion-resistant structures
formed under laser quenching, we studied changes in the structure, mechanical properties (hardness, abrasion
resistance), and electromagnetic parameters as functions of the depth of the laser-processed zone in the
preliminarily bulk-quenched and low-tempered steel
òï15
.
Laser surface processing of items characterized by rapid wear-out offer the following advantages: Subsequent
tempering (mandatory after standard furnace quenching) can be abandoned, and untempered
quenched items characterized by the maximum abrasion resistance can be used under practical conditions
[10]. However, the items that are subject to cyclic loads during operation may be tempered after laser hardening
[11, 12]. The laser-hardened surface may be heated in the process of polishing, welding, or other manufacturing
operations as well as during operation of items made of ball-bearing steels [13]. Therefore, this
study pursued one more goal: examination of the possibilities of using nondestructive methods to forecast
the abrasion resistance of steel
òï15
that has undergone laser and bulk quenching and tempering in the
temperature interval 75–600
°
C.