Effect Of Ultrasonic Deep Rolling Spindle Speed On The Tribological Properties Of Sprayed Metal-ceramic Coatings In High Temperature Environments

Plasma-sprayed Ni/WC coating has the advantages of high hardness and high wear resistance of ceramics.It is widely used in aerospace,transportation,industrial gas turbines,and marine protection to improve the wear resistance of parts.However,the sprayed coating has a layered structure,internal pores,cracks,and other defects,and is prone to sudden or premature wear failures such as cracking and spalling during service.To improve the friction and wear properties of plasma sprayed Ni60+15WC coating on 45#steel substrate,and to study the relationship between spindle speed and the frictional and wear properties of the coated surface in the High Temperature Ultrasonic Deep Rolling（HT+UDR）process,different spindle speeds（173 r/min,248 r/min,and 360 r/min）were set to strengthen the Ni/WC coating by HT+UDR.The results show that:（1）Ni/WC coating showed improvement in surface profile after normal-UDR,although cracking occurred on coating surface and in surface layer;physical phase of coating surface remained unchanged and coating mechanically bonded to substrate;Ni/WC coating showed flatness and denser internal structure after HT+UDR.The Fe and Cr elements diffuse at the interface between the coating and the substrate,and the coating and the substrate form a metallurgical bond.New hard phases such as Cr₇C₃,Cr₂B₃ and Cr B appeared on the coating surface.The hardening effect of HT+UDR on Ni/WC coating decreases with the increase of spindle speed.The specimens with HT+UDR 173 r/min have the smoothest surface and the densest internal structure.（2）Spindle speed mainly influences the intensity of machining of the tool head in the circumferential direction of the Ni/WC coating.Coating properties after high temperature assisted ultrasonic rolling decreased with increasing spindle speed.The micro-hardness and the residual compressive stress of the coating decreased with increasing spindle speed;the surface roughness and the pore content increased with increasing spindle speed.HT+UDR173 r/min specimens showed the best performance.Compared with the unrolled specimen,the surface roughness of the HT+UDR 173 r/min specimen decreased to 0.425μm,a drop of 49.04%;the surface microhardness increased to 873.9 HV_0.2,an increase of 242.5 HV_0.2;the surface residual stress showed a compressive stress value of-404.2 MPa;and the porosity decreased by 1.5346%.（3）UDR has a good anti-wear effect on Ni/WC coating,which can effectively improve the friction and wear properties of the coating.The friction and wear properties of the HT+UDR 173 r/min sample are the best,with an average friction coefficient of 0.03904 and a wear loss of 5.4 mg,which is 64.23%lower than that of the unrolled coating.The Ni/WC coatings before and after UDR have abrasive wear,spalling wear and oxidation wear mechanisms during the friction and wear process.The wear mechanisms of the unrolled and room temperature ultrasonic rolling coatings are mainly abrasive wear and spalling wear.The wear mechanism of the HT+UDR coating is primarily abrasive wear,accompanied by a little of spalling wear.