tailieunhanh - Volume 18 - Friction, Lubrication, and Wear Technology Part 19

Tham khảo tài liệu 'volume 18 - friction, lubrication, and wear technology part 19', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Fig. 8 Dry pin-on-ring test used to evaluate effect of microstructure on the wear resistance and the hardness of pearlitic steel pins. Test parameters pressure P MPa ksi velocity v m s ft s atmosphere dry air. P pearlite P F pearlite and ferrite. Source Ref 6 In lubricated block-on-ring wear experiments with pearlitic carbon steel where deformation wear was the principal wear mode pearlite was observed to minimize the depth of extreme plastic deformation Ref 8 . During heavy working the interlath spacing in pearlite will decrease and the ferrite will work harden. Thus the hardness of pearlite increases with decreased lamellae spacing Fig. 9 and the structure tends to resist recrystallization Ref 9 . The result is a thinner zone of heavy working and a smaller volume of metal extruding out of the contact zone. Fig. 9 Abrasive wear resistance and bulk hardness of C steel as a function of pearlite interlamellar spacing. Abrasion data obtained using pin abrasion test apparatus with pressure P of 710 kPa 105 psi two different 220-mesh abrasives flint 96 to 99 Si and silicon carbide used in separate tests. Source Ref 6 Under boundary lubrication conditions where heavier loads are possible than under dry conditions a pearlitic structure with tight interlamellar spacing in the pearlite phase is appropriate to minimize the depth of shear instability. Shear instability Ref 10 below the contact surface is the source for deformation wear. Austenitic steels with varying manganese content show wear resistance to be a function of manganese content. The resistance depends on the transformation of the unstable austenite to martensite that is the hard wear-resistant phase . Manganese tends to promote the retention of room-temperature austenite in carbon steel. The retained austenite is unstable and will transform to martensite under heavy deformation. The room-temperature austenite becomes more stable as the manganese content of the alloy is increased. .