Many different engineered components require surface engineering. The reason for this is because gears and beatings transmit energy by sliding, rotating or rolling when they engage in metal-to-metal contact between components. This contact can be a rolling, sliding or pushing force against a complementary component. Asperities on these surfaces introduce what is known as friction inefficiency into the mechanical transfer of energy, resulting in energy loss which results in heat generation. When there is increased frictional resistance at the contact points, then there’s premature wear. Further, with increased wear, there will also be efficiency declines.
During the 1950’s and 60’s, forced emission was used to amplify microwaves. Ion implantation was used along with methods of chemical vapor deposition from the gas phase. And besides plasma, detonation gun spraying was also used. In the late 60’s, there was rapid development of technologies and methods, using a direct beam of high power density, solar energy, infrared radiation, plasma, ion beam and coherent photon beam. The new methods in surface engineering are based on the latest technologies.
Commonly used in metal finishing for genetic deburring, you will find vibratory bowl finishing which can be used to superfinish the surfaces of complementary components to an isotropic (random) finish when using nonabrasive, high-density media in conjunction with an isotropic superfinishing chemistry. This improved surface engineering tactic increases the energy and motion transfer efficiency in the metal-to-metal contact area. Basically it reduces friction.
Traditionally grinding is the final metal finishing operation performed on metal-to-metal contact surfaces like gears and roller bearings, resulting in a surface with a unidirectional pattern corresponding to the final grinding operation direction. Grinding with finer grinding wheels is repetitious, expensive, and ineffective as it results in a surface that has more, closer-spaced rows of shorter height asperities. When placed into operation for the first time, ground components have a minimal area of initial metal-to-metal contact at asperity peaks where contact stress is concentrated.
But during this process, asperity refinement occurs in a chemically accelerated vibratory finishing process. Just as one example, when parts need to be refined, such as automotive camshafts, gears, bearings rings/pinions, or valve springs, are placed into a vibratory machine containing high-density, nonabrasive media.
However, isotropically prepared metal parts have an improved metal-to-metal contact pattern, because asperities have been removed. What is the result? The final surface is much smoother, with contact stress in any one location diffused over a wider area. This is all due to an improved contact pattern. Isotropic superfinishes achieve the highest performance ratings in terms of friction, noise, heat, and wear and tear on the gear, bearing, and turbine industries. Especially successful on parts that operate in high contact loading, metal-to-metal applications, this proven surface engineering process is currently used by many industries.
In summary, it matters not how well gears are designed and manufactured, because there will always be gear corrosion – and this could result in a catastrophe. Corrosion is sporadic and a rare event and often difficult to observe in the root fillet region or in finely pitched gears with normal visual inspection, it may easily go undetected. Super finishing by surface engineering experts can mitigate the damaging effects of corrosion.
This article was added on Friday 16 July, 2010.
