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Materials for motorcycles
Published in Andrew Livesey, Motorcycle Engineering, 2021
Low-carbon steel is soft, ductile, and malleable and therefore can be easily formed into shape. It cannot be hardened and tempered by heating and quenching, but it can be case-hardened and it will work-harden. Case-hardening is a process of coating the surface of the steel component with a high-carbon content chemical and heating it to a set temperature. When the component cools, the surface is hard like high-carbon steel and the underside remains soft and malleable. This process is used on hub bearing surfaces. If you look at a hub cone closely, you will be able to see the different colors of the metal. The advantages of this are that the axle and cones can be made of low-carbon steel, which is both easier to machine and cheaper to buy, and then given a wear-resistant surface for the bearing.
Materials for bicycles
Published in Andrew Livesey, Bicycle Engineering and Technology, 2020
Low carbon steel is soft, ductile and malleable and, therefore, can be easily formed into shape. It cannot be hardened and tempered by heating and quenching; but it can be case-hardened and it will work harden. Case-hardening is a process of coating the surface of the steel component with a high carbon content chemical and heating to a set temperature. When the component cools, the surface is hard like high carbon steel and the underside remains soft and malleable. This process is used on hub bearing surfaces; if you look at a hub cone closely, you will be able to see the different colours of the metal. The advantages of this are that the axle and cones can be made of low carbon steel, which is both easier to machine and cheaper to buy and then giving a wear resistant surface for the bearing.
Common Heat Treatment Practices
Published in Bankim Chandra Ray, Rajesh Kumar Prusty, Deepak Nayak, Phase Transformations and Heat Treatments of Steels, 2020
Bankim Chandra Ray, Rajesh Kumar Prusty, Deepak Nayak
A large number of machine components like gears require a combination of various properties such as high surface hardness and wear resistance along with excellent toughness and impact resistance. High-carbon steels can provide high surface hardness and wear resistance after suitable heat treatment, but impact strength is poor. On the other hand, low-carbon steels provide high impact strengths but very low surface hardness and wear resistance. Surface hardening and case hardening methods are commonly used to impart this combination of properties. While case hardening changes the chemical composition of the surface layers, surface hardening does not alter the chemical composition of the steel but includes phase transformation by fast heating and cooling of the outer surface. Conventional case hardening methods are carburizing, nitriding, and cyaniding or carbonitriding. Surface hardening processes are flame hardening, induction hardening, laser hardening, and electron beam hardening. Let us discuss some of these methods in detail.
Crack initiation and early propagation in case hardened sintered PM steels under cyclic load
Published in Powder Metallurgy, 2023
Anders Holmberg, Urban Wiklund, Per Isaksson, Åsa Kassman Rudolphi
Machine components of PM steels, such as gears, are almost always hardened in some way. The most common is case hardening, which provides the surface with a hard, wear-resistant martensitic layer while keeping the ductility and toughness of the interior. The case hardening procedure involves surface heating, resulting in phase transformations from ferrite and pearlite to austenite. As the material is then rapidly cooled, the austenite is transformed into martensite. The relevant structure to relate to after case hardening is thus prior austenite grains rather than prior particle grains. For sintered steel, the pores, if they are large enough, will pin down grain boundaries and retard austenitic grain growth. Therefore the initial particle size practically restricts the maximum size of the austenite grains [10,11], meaning that the size of a prior austenite grain depends on the size of the prior particle grain size.
Accelerated Testing to Investigate Corrosion Mechanisms of Carburized and Carbonitrided Martensitic Stainless Steel for Aerospace Bearings in Harsh Environments
Published in Tribology Transactions, 2020
Armen Kvryan, Nicholas A. Carter, Hitesh K. Trivedi, Michael F. Hurley
P675 is a carburizable MSS that requires tailored surface treatments to meet specific aerospace performance requirements via case hardening (Jaing, et al. (17); Chakraborty, et al. (22); Isfahany, et al. (23)). With a chromium content exceeding 12%, P675 is considered “stainless” due to spontaneous oxide film formation that passivates the steel (Jones (24); Revie and Uhlig (25)). During carburization, inward carbon diffusion causes the formation of intermetallic carbides to precipitate in the case region (Peissl, et al. (26); Godec, et al. (27); Han, et al. (28)). Case hardening introduces compressive stresses in the surface and allows the bearings to perform under higher loads and rotational speeds and suppresses surface crack opening (Bhadeshia (9); Klecka, et al. (29); Smallman and Ngan (30)). However, coarse carbides and nitrides are also associated with poor fatigue performance and premature fatigue spalling (Bhadeshia (6); Ebert (7); Parker and Bamberger (31)). The resulting performance characteristics of P675 are determined by the specific heat treatment schedule to, in part, optimize the type and manner of carbide population present in the case region.