Process variability in honing of cylinder liner with vitri fied bonded diamond tools
L.Sabri a ,b ,M.El Mansori a ,⁎
a Arts et Métiers ParisTech,LMPF-EA 4106,Rue Saint Dominique,BP 508,51006,Châlons-en-Champagne,Cedex,France b
Renault s.a.s,Direction de l'Ingénierie Mécanique,67rue des bons raisins,92500Rueil Malmaison,France
a b s t r a c t
a r t i c l e i n f o Available online 19May 2009Keywords:
Honing variability Cylinder liner wear Surface finish
Vitri fied bonded diamond stone
With the increasing use of ultra-hard abrasives and the introduction of more powerful and rigid machines,honing process is spreading its performances.In industrial honing of cylinder liners for internal combustion engines,the degree of penetration that Metallic Bonded Diamond (MBD)abrasive stones have experienced compared to conventional Vitri fied Bonded Silicon Carbide (VBSC)tools is obvious.The long tool life of metal bonded diamond sticks is however balanced by its main role in producing torn and folded metal without cutting-effect finish.To simultaneously reduce folding and remove the stock with improved stone life,an experimental investigation is reported on the process variability in finish honing behavior due to stone inconsistency and nature of its properties.We consider the achievable performances by finish honing of cast iron liners with a new abrasive stone.This superabrasive consists of micro-sized diamond abrasives which are bonded with vitri fied bond (VBD).By selection of finer grit abrasive while honing with VBD tool,conditions could be created that gave a cutting-effect finish to the diamond honing and minimized the folding over.
©2009Elsevier B.V.All rights reserved.
1.Introduction
Honing is a demanding operation,often involving a great deal of interrupted multistage surface formation which is decisively in fluenced by the abrasive grain types [1–3].When honing technology was developed 50years ago,it was primary used as a finishing operation.But now,honing is responding towards the challenge of higher productivity and also making progress as a stock removal process [2,3].Such developments lie in a new generation of abrasives,honing centers,and process improvements.Abrasive stones used have to be also selected appropriately,according to applications.For automotive crankcases,two types of abrasive can mainly be differentiated when cylinder liners are being honed.These are superabrasives –Metal Bonded Diamond (MBD)and conventional abrasives –Vitri fied Bonded Silicon Carbide (VBSC)[2].The use of Metal Bonded Diamond sticks ful fils the tool life requirement.However,the main impediments of these sticks are the turn and folding of the material spread which leads to seizure.Indeed,MBD stones have higher bonding strength between the diamond grits and the bonding matrix and consequently longer tool life.Therefore,this structure retards the exposure of new cutting edges when the diamond grits become dull during honing process [3].Severe friction between the metal bond and the workpiece is thus induced.Accordingly,the honing ef ficiency is reduced by creating the so-called “Blechmantel ”phenomenon.It consists of the presence of cold work material smeared out on cylinder liners which is undesirable as it seals the oil-bearing honing grooves and closes the graphite inclusions [4].Besides,even vitri fied bonds also have higher bond strength in comparison with others types of bonds,the high elastic
modulus and low fracture toughness of the glass bonding materials facilitate a self-dressing capability of the stone [5].The stick becomes then excellent in discharge capability of honing chips due to the formation of numerous pores between the grains.Hence,high surface quality is produced to the detriment of a lower tool life [6,7].On this basis,new abrasive stone with vitri fied bonded diamond (VBD)has been developed in order to combine the excellent properties of vitri fied bond to those of diamond grains.It consists of micro-sized diamonds embedded in a SiC matrix and it is investigated in regard to its finish and wearing performance while honing car iron liners.Also,the involved cutting effect with these new superabrasive hones is considered to evaluate the inherent process variability.2.Experimental
In this work,honing experiments were carried out on a vertical honing machine with an expansible tool (NAGEL no.28-8470)(Fig.1).The workpiece consists of cylinder liner of lamellar gray cast iron engine crankcase after boring and rough honing operations.Two sets of instrumented finish honing tests were performed with two types of abrasive stones,namely:
1.Vitri fied Bonded Silicon Carbide (VBSC)with an average grit size of 110µm (Fig.2-a).It is a IAS65/100I8S conventional stone with an initial mixture of 65vol.%of aluminum oxide and 35vol.%of green silicon carbide which corresponds to a soft grade,a large openness of the structure (8)and having a vitri fied bond resulting from a special treatment by impregnation with sulfur.
2.Vitri fied Bonded Diamond (VBD)with an average grit size of 107µm (Fig.2-b).This superabrasive hone is new type of composite
Surface &Coatings Technology 204(2009)1046–1050
⁎Corresponding author.Tel.:+33326699181;fax:+33326699176.E-mail address:mohamed.elmansori@chalons.ensam.fr (M.El
Mansori).0257-8972/$–see front matter ©2009Elsevier B.V.All rights reserved.doi:
10.1016/j.surfcoat.2009.05.013
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