| With the development of worldwide industrialization and economic integration,some new theories and patterns such as "Industry 4.0" and "China Manufacturing 2025" are emerging,which sets higher requirement for energy conservation,environmental protection and pollution abatement.Diesel engine companies are facing tremendous impact and pressure because many countries introduced stricter and stricter laws and regulations to limit the vehicle especially the high-power diesel engine vehicle emissions.As a result,it is important to improve the production quality of diesel engine,save processing consumables and reduce production cost in the manufacturing process of diesel engine.As the core part of diesel engine,crankshaft is under the impact of the centrifugal force,gas inertia force and reciprocating inertial force during working process.In order to satisfy these strict usage requirements,the manufacturing material strength,stiffness and tenacity of the crankshafts must be high.Therefore,the tool wear is serious during machining crankshafts.Investigating the tool wear mechanism,choosing the suitable cutting tool material and cutting parameters for the processing of crankshafts is a efficient way to reduce tool wear and cost of production.In this study,the fracture morphology and wear mechanisms of worn cuttings tools in processing crankshaft were investigated.The wear properties of five different coatings were compered and the most suitable tool coating for machining 42CrMo steel was chosen.The orthogonal turning experiment under constant material removal volume(MRV)condition was carried out.The prediction model between tool wear flank wear and the cutting parameters was proposed.The main research contents are shown as following:(1)Based on the tool wear mechanism during machining 42CrMo steel material,five cutting tool coating materials were chosen.Using SEM and EDS,the surface topography,composition and structure of these coatings were observed.Aimed at reducing diffusion wear,element diffusion experiment between five coating materials and 42CrMo steel were carried out.The results showed that the diffusion distance increases as the increase in temperature,the titanium(Ti)element diffused for a longer distance than iron(Fe)element,and the TiN-TiCN-TiN-Al2O3-TiN coating material manifested the shortest diffusion distance and less decline of microhardness.Aimed at reducing abrasive and adhesive wear,an intensive study on the friction and wear properties of five nitride coatings against 42CrMo steel was performed.It indicates that the TiN-TiCN-TiN-Al2O3-TiN and TiAIN had the minimum friction coefficient and wear rate,the wear resistance of TiN-TiCN-TiN-TiCN-Al2O3 and TiN-TiCN-TiN-Al2O3-TiN are better than that of the other coatings,and the wear mechanism mainly include abrasive wear,adhesive wear and oxidation.Aimed at reducing coating peeling,adhesion strength of coating-substrate was investigated.The adhesion strength of TiN-TiCN-TiN-TiCN-Al2O3 and TiN-TiCN-TiN-Al2O3-TiN were larger.(2)Preliminary turning experiment was carried out,from which the relationship between tool flank wear(VB)and material removal volume(MRV)was determined.The results also showed that the tool wear divided into two stage(intense wear stage and stable wear stage).Orthogonal turning experiment of 42CrMo steel under constant MRV was carried out,the significance level of cutting parameters to VB list as:ap>f>v.The optimal parameter combination to minimize VB is v=200m/min,f=0.2mm/r,ap=1.5mm.Based on BP neural network,the prediction model between VB and cutting parameters was built and verified.(3)The tool wear morphology and mechanism in crankshaft machining was investigated.The tool wear morphology mainly includes rake face wear,flank face wear and coating peeling.The tool wear mechanism mainly includes diffusive wear,oxidation wear and scratch.The tool wear extent was between 0.5mm and 0.8mm.In this paper,the tool wear morphology and mechanism in crankshaft machining was investigated,the most suitable coating material for machining 42CrMo steel was chosen and the prediction model between VB and cutting parameters was built.The research is benefit to reasonably choose cutting parameters and tool coatings,reduce tool wear and raise processing quality. |
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