Carburizing Microstructures and PropertiesGeoffrey Parrish Contents Preface to First Edition. 6. Interaction between furnace atmosphere and steel. 7. Function of the furnace atmosphere. 7. The carburizing process. 7. Relationship between carbon activity . in the gas carburising and induction hardening processes so as to minimize the geometrical distortions below the hardened surface in the Gas carburizing and.
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PDF | This research is concerned with the effect of different carburizing mediums on fatigue strength of low carbon alloy steel for its Download full-text PDF. Gas carburizing is one of the surface engineering techniques widely used in the process Key words: Quality, Gas carburizing, Process variables, Optimization. Presentation on Carburizing (Heat Treatment Process). CARBURIZING Presented To Engr. Ubaid-ur-Rehman Ghouri . Download.
Pack carburising is a time-consuming process which limits its commercial applications. The aims of present study were to increase the efficiency of pack carburising process and to decrease the time of carburising. Pack carburising of low-carbon steel was carried out by embedding low-carbon steel samples in carburising compound consisting of carbon black nanoparticles as carbonaceous matter and barium carbonate as energiser.
The effect of time of carburising and carburising medium on microstructure, hardness and case depth of the samples was investigated.
The samples carburised using carbon black nanoparticles showed higher hardness than the samples carburised using acetylene gas or charcoal-based carburising mixture. Keywords This is a preview of subscription content, log in to check access. Preview Unable to display preview. Download preview PDF. References Totten G.
Butterworth-Heinemann, Oxford Google Scholar 3. A gear tooth is a good example in which each of these must be considered.
Some significance has been placed on the residual stresses developed during carburizing because these are additive to the applied stresses. Why Carburize Case-Harden? With some through-hardening steels, it is possible to develop hardnesses equal to the surface hardnesses typical of case-hardening parts; however, machine parts for example, gears would not be able to transmit as much load as would case-hardened parts.
This is because case hardening produces significant compressive-residual stresses at the surface and within the hard case, whereas with through hardening, the residual 2 I Carburizing: Microstructures andProperties stresses are much less predictable.
Furthermore, high-hardness through-hardened steels tend to lack toughness; therefore, in general , throughhardened and tempered steels are limited to about 40 HRC to develop their best strength-totoughness properties.
To produce compressiveresidual stresses to a reasonable depth in a through-hardening steel, one must resort to a local thermal hardening process, such as induction hardening, or an alternative chemicothennal treatment, such as nitriding.
When induction hardening is used for gears, for example, the preferred hardness distribution is generally to have about 55 HRC at the surface and 30 HRC in the core Ref 1 ; consequently, parts so treated do not have a contact strength or wear resistance that are quite as good as in carboozed and hardened parts.
The induction hardening process is useful for large parts that need to be surface hardened but would distort or grow excessively if carburized and hardened.
Typical gear steels surface hardened by induction are and initially in the hardened and tempered condition , and typical case depths range from 1. Nitriding is a means of producing a hard surface with high surface compressive-residual stresses.
It is a subcritical temperature process, and consequently, it is an essentially distortionand growth-free process. The degree of hardening relates rnainly to the chromium content of the steel so that a carbon steel will nitride harden only a little. Unfortunately, the cases that can be achieved due to nitriding are shallow 0.
The shallowness of the case limits the range of application of nitrided steels. For gears, the limiting tooth size is about 2 rom module However, within its safe range of application, the case shallowness provides good bending fatigue, contact fatigue, wear, and scuffing resistance. Carbon case hardening can be employed to achieve a wide range of effective case depths up to greater than 4 rom in a wide range of steels limiting core carbon is normally 0.
The contactfatigue and bending-fatigue strengths are regarded as superior to induction-hardened surfaces and to nitride-hardened surfaces above a certain size limit.
The drawbacks with carbon case hardening are distortion, growth, and costs. Distortion and growth are controlled as much as possible during heat treating by the use of dies and plugs and finally corrected by a limited amount of grinding. The costs are justified in the product to obtain a high power-to-weight ratio and durability.
An indication of the advantages of case hardening, compared with through hardening, is shown in the torque-speed plots of Fig. Here, the safe operating zone for case-hardened gear sets is much greater than it is for throughhardened steels. Alternatively, size for size, the case-hardened gear set will be much more durable.