Subscribe to RSS
UnitedStates Germany Russia India Turkey SouthAfrica England Netherlands Philippines Belgium Australia Brazil Spain China Kore

Surface engineering combats friction and wear

BARDEN CORPORATION | PLYMOUTH UK

Barden surface eng

Working together with recognized leaders in advanced coatings and surface treatments has enabled Barden to provide specialized Surface Engineering Technology in support of the most demanding applications for precision bearings. Gary Hughes, Product Engineering Manager at The Barden Corporation, outlines the latest developments.

Engineering surfaces are neither perfectly flat, smooth nor clean. therefore, in terms of rolling bearings, when two surfaces come into contact, only a very small percentage of the apparent surface area is actually supporting the load. This can often result in high contact stresses, which lead to increased friction and wear of the component.

Surface engineering is the design and modification of a surface and substrate in combination to give cost effective performance improvements that would not otherwise be achieved. Surface engineering recognises that the properties and characteristics of a surface are contained within a relatively thin ‘skin’. It is therefore the properties of the surface layers, not the bulk material, which determine and control system performance.

In all types of environments, from aerospace to offshore – where precision bearing systems are challenged by harsh, difficult operating conditions such as marginal lubrication, aggressive media and hostile environments – surface engineering processes can provide improved tribological performance for protection against potential friction and wear problems.

The scope of surface engineering technology encompasses a whole range of coatings and surface treatments that can be applied to engineering surfaces in order to combat friction, prevent corrosion and reduce wear. The resulting benefits are improved performance, lower running costs and longer service intervals. Surface engineering processes generally fall into one of five basic categories:

Transformation processes (thermal and mechanical)

Hard coatings

Soft films

Diffused layers

Specialised treatments

For this article, transformation processes (i.e. the metallurgy of steels and the effects of processes and heat treatments) about which much is already documented, will be left aside, enabling a focus on the equally important, but (arguably) more dynamic, areas of coatings and other surface treatment technologies.

Barden surface eng

Hard Coatings
Because the wear rate of a material is proportional to the load applied to it, and inversely proportional to its hardness, one obvious way of reducing wear on bearing components is to increase the hardness at their surface. This is primarily achieved using hard coatings such as electro less nickel plating, hard-anodizing, thin dense chrome, plasma nit riding, arc evaporated titanium nitride, carburizing and carbo-nitriding.

Other hard coatings, such as titanium carbide or galvanized zinc, can also be used to prevent corrosion and delay lubricant degradation. however, it is incorrect to assume that all processes offering good wear resistance also confer anti-corrosion properties. some hard coatings can render the substrate steel more susceptible to corrosion. Conversely, materials offering corrosion protection may not necessarily provide good resistance to wear. This is evidenced by the use of soft metal films, which have negligible wear resistant capability, but are, nevertheless, effective in combating corrosion.

Hard coatings can also be used to prevent fretting (i.e. small amplitude oscillations or vibrations). The fretting motion disrupts the naturally present surface oxide films and exposes highly reactive metal, which then rapidly oxidizes and is, in turn, disrupted by the motion. Metal oxide wear particles are usually harder than the original material and can cause the system to degrade through three-body abrasion. Furthermore, the oxide particles naturally occupy greater volume than the original metal and hence there is a risk of seizure on close-tolerance mating parts. Hard surface engineering coatings, by being very effective at preventing fretting in the first instance, can prevent this from happening.

Soft Films
In contrast to hard coatings, soft films are primarily used to provide solid lubrication for bearings in extreme applications where traditional fluid lubricants would be rendered ineffective. These offer advantages in that their friction is independent of temperature (from cryogenic to extreme high temperature applications), and they do not evaporate or creep in terrestrial vacuum or space environments.

The solid soft film lubricant can either be applied directly to the surface or transferred by rubbing contact from a sacrificial source such as a self-lubricating bearing cage. Examples of these two processes include the application of physical vapor deposited MoST and WS2 and Barden’s PTFE-based BarTemp polymeric cage material, Vespel or Torlon. The processes are complementary and have been used successfully in a variety of extreme aerospace application.

Diffusion Layers
The value of diffusion processes is that they can effectively reduce the amount of wear on engineering components, thereby extending their useful life. The process itself is a function of time and temperature and is limited only by the natural saturation limit of the substrate.

Traditional diffusion processes such as case-hardening rely on the diffusion of elements such as nitrogen and carbon into the surface. Examples include nitriding, boronising and carburising. In contrast, high-energy processes such as ion-implantation can be used to increase the relative atomic per cent of carbon and nitrogen into the surface beyond the limits of traditional diffusion techniques.

for applications requiring good anti-corrosion performance, Barden also uses advanced material technologies such as its unique X-Life Ultra high nitrogen steel bearings. In controlled salt-spray tests, these bearings offer superior corrosion protection to those manufactured from industry standard steels such as AISI 440C.

Specialized Processes
Specialized processes is a term that describes the way in which surface engineering techniques and processes can be combined to further enhance the properties of the bearing system.

For example, multi-layer coatings can be employed to enhance the physical and tribological characteristics of the surface. The success of such techniques relies on the avoidance of distinct layers by generating a graduated o diffused interface between different materials. Similarly, keying layers such as nickel or copper are frequently used to improve the adhesion of soft films to hard or passivized substrates.

Specialized coatings can also be applied to increase thermal conductance, reduce reactivity to the atmosphere and to improve optical transmission or reflectance characteristics. The properties of ceramics and metals can be combined in the form of ‘cermets’ such as NiSiC and NiAI2O3 in order to realize outstanding mechanical and chemical performance.

Which process is best for the application?
Because of the large number of coatings and surface treatments that are available to combat friction, corrosion and wear, it is often difficult for designers to select the optimum process for a particular application. To help, Barden has identified four steps to approach the problem:

  1. Identify the limiting factor(s) on bearing life – friction, wear and corrosion
  2. Prepare a list of candidate coatings and surface treatments, eliminating those considered unsuitable on grounds of thickness and/or processing requirements (e.g. high temperature)
  3. Where possible, consult previous case histories of similar applications for verification of process suitability and produce a shortlist of preferred candidates
  4. Refer to detailed surface engineering specifications to select the optimum process

In addition, in all cases, particularly where there is little or no proven heritage of a process for the application, it is recommended that suitable qualification trials be carried out before a respective process is selected, in order to verify its suitability. Cost and availability will also need careful consideration here.

The Future
The role of surface engineering in rolling bearing technology will become more pivotal in the future as new bearing designs become progressively smaller, but are still required to run faster, carry higher loads and operate reliably for longer periods, even under conditions of marginal lubrication. Whilst surface engineering technologies have been pivotal to the success of deep space applications such as spacecraft engines, similar performance demands are now being regularly encountered in terrestrial application. What this illustrates is the rapid pace of development of bearing technology, driven by market demands, and the equally important role that surface engineering is set to play in helping to achieve these demands.

 

source: Barden Bearings

0 commentsback to post

banner

Add your comment

Nickname:
E-mail:
Website:
Comment:

*

Other articlesgo to homepage

무선 진동 분석

무선 진동 분석(0)

PRÜFTECHNIK, VIBCONNECT RF에 새로운 기능 추가 ISMANING – 2014년 3월 25일- 새로운 펌웨어 업데이트를 통해 PRÜFTECHNIK의 무선 온라인 컨디션 모니터링 시스템인 VIBCONNECT RF가 한층 강화됐다. 무선 기술이 장착된 VIBCONNECT RF는 장거리 진동 측정 데이터를 무선으로 전송해야 하는 어플리케이션에 완벽하게 활용될 수 있다. VIBCONNECT RF 의 최신 펌웨어 업데이트는 몇 가지 강력한 특징을 갖는다. 상태 및

진동 측정 장비를 이용한 베어링 윤활처리 모니터링

진동 측정 장비를 이용한 베어링 윤활처리 모니터링(0)

윤활처리된 베어링의 재윤활 시기 자동 연속 윤활 시스템이 점점 더 많은 대형 베어링 들에 장착되고 있지만, 그림 1에서 보여지는 것과 같은 팬에 적용될 경우 비용면에서 효율적이지 않다. 그림 1: 팬 일반적인 팬들은 특정 간격으로 수작업에 의해 윤활처리 되지만, 그렇다면 이런 간격은 얼마나되어야 하는가? PRÜFTECHNIK의 온라인 컨디션 모니터링 시스템이 해답을 제시해 줄 수 있다. 예를 들면,

신뢰성 향상을 위한 윤활 관리

신뢰성 향상을 위한 윤활 관리(0)

공장 내 윤활처리 작업은 공장 뿐만 아니라 기기의 신뢰성에 직접적인 영향을 미친다. 기계 내에서 윤활유가 오염을 최소화 하고, 아무런 화학적 분해없이 효과적으로 작동할 때, 부품의 마모도는 감소하고 기기의 신뢰성은 향상 될 것이다. 마모도 감소와 기기 신뢰성을 향상시키기 위해서는 효과적이고 깨끗한 평균 윤활 막 두께, 즉 좋은 점도를 보호하고 유지하는 것이 가장 중요하다. 윤활 신뢰성이란? 베어링

사례연구: 펌프모터 베어링의 성능 향상

사례연구: 펌프모터 베어링의 성능 향상(0)

이 연구는 STARWOOD Inc.의 수석 엔지니어인 mr.Selcuk Karabay에 의해 진행됐다. 결과: 프레스 기계에 사용되는 핫오일 펌프 모터는 작동온도가 90-100° C에 달했고, 진공 펌프 모터의 경우 100-110° C이며, 작동이 계속적으로 멈추는 현상을 보였다. 또한 높은 작동 온도로 인해 고온의 베어링이 6개월만에 파손되기도 했다. 테스트 핫오일 펌프 모터 테스트 진공 펌프 모터 파손 원인: 상황 분석 후,

볼베어링 & 에저지절약

볼베어링 & 에저지절약(0)

요즘 전 세계적으로, 환경에 미치는 영향을 최소화 하기 위해 그린상품에 대한 수요가 증가되고 있다. 이러 추세는 앞으로도 계속될 전망으로, 기계 및 공장들의 생산능력 향상은 큰 도전과제가 될 것이다. JESA SA는 볼베어링과 폴리머컴포넌트의 설계및 제작에 특화된 회사로써, 성능이 향상된 볼베어링을 제작하기 위한 연구를 시작했으며, 다양한 어플리케이션에 대규모로 사용되는 구성요소들과 깊은 관련이 있어, 잠재적인 에너지 절감이 예상된다.

더보기

문의사항

Social networks

자주찾는 카테고리

Legal Notice

© 2012 BEARING NEWS All rights reserved.