It was found out that cobalt in the concentration limited to about 5% results in increasing the secondary hardness effect by 1.6 1.9 HRC, depending on a grade of steel.
The reason for the secondary hardness effect is the precipitation of dispersive carbides of the M4C3 type in the matrix of the tempered martensite and martensite transformation of the retained austenite, which occurs during cooling from tempering temperature.
The maximum secondary hardness effect about 66.3 67.6 HRC, depending on a grade of steel, increases the hardness by about 2 4 HRC, compared with the hardness in the as-quenched state, and occurs in each steel after tempering at 540°C and austenitizing at 1240°C during 100 s.
Combined with an evaluation of mechanical properties of the deposited coatings like residual stress and Vickers hardness, the effects of plasma ion bombardment are presented and discussed.
The hardness enhancement effect was brought by the HIPIMS technique.
High levels of hardness may effected water supply system, excessive soap consumption, calcification of arteries and cause urinary concretions, diseases of kidney of bladder and stomach disorder (CPCB 2008).
Micro-hardness testing results show that the hardness enhancement effect takes place at the specific period of 15 nm, 100 nm and 200 nm.
Nanoindentation tests showed that the presence of Cr can significantly change coating hardness: this effect can be correlated with compositional and microstructural changes.
