Dn. Hanlon et al., THE EFFECT OF PROCESSING ROUTE, COMPOSITION AND HARDNESS ON THE WEAR RESPONSE OF CHROMIUM BEARING STEELS IN A ROLLING-SLIDING CONFIGURATION, Wear, 203, 1997, pp. 220-229
The commercial attractiveness of rolls with greater resistance to wear
and fatigue damage is substantial, providing reduced rolling mill dow
n times, increased roll life, reduced product surface defects and impr
oved stock gauge tolerances. Relatively little is known about the wear
mechanisms of these materials which limit the useful life of cold rol
ling mill work rolls. Two steels of composition 0.8%C/3%Cr and 0.8%C/5
%Cr, which are representative of industry standard materials, have bee
n tested in a rolling-sliding configuration (slippage, 8%) against a h
igh speed steel (M2) counterface. A comparison has been made between s
amples manufactured by conventional processing (casting and forging) a
nd by spray forming. Spray forming provided a microstructure similar t
o that of the heavily forged material but with a finer average carbide
size (134 nm in the spray formed and 317 nm in the forged, both for t
he 3%Cr steels) and the spray formed material did not contain the occa
sional coarse carbides (similar to 2 mu m) found in the forged materia
l. The increase in Cr content from 3% to 5% changed the carbide from (
Fe,Cr)(3)C (3%Cr steel) to (Fe,Cr)(7)C-3 (5%Cr steel) in both spray fo
rmed and forged materials. However, both the carbide size and carbide
type had little effect on wear rate when tested in the quenched and te
mpered condition. Tempering of the quenched steel was undertaken in th
e temperature range 200-500 degrees C, which yielded hardness in the r
ange 540-890 H-v for the 3% Cr steel and 470-880 H-v for the 5% Cr ste
el. The wear coefficient decreased significantly for an increase in ha
rdness from to 470 H-v (k approximate to 1.72 x 10(-5) mm(3) N-1 m(-1)
) to 750 H-v (k approximate to 1.35 x 10(-6) mm(3) N-1 m(-1)) but only
fell slightly for hardness values above 750 H-v. The friction coeffic
ient was 0.49-0.63 irrespective of load or material temper. Characteri
sation of worn surfaces indicated that surface strain was limited to a
depth of similar to 5-15 mu m In the hardest conditions, the wear deb
ris was predominantly oxide, while the soft tempers produced metallic
delamination sheets as well asoxide. The wear behaviour of the four ma
terials is discussed in relation to the microstructure. (C) 1997 Elsev
ier Science S.A.