Research And Analysis Of Stress Within Thermal Spray Coating

In recent years,with new technology and new materials be developed and applied the thermal spray coating paly some roles in corrosion resist,wear resist,high temperature resist etc.,in more and more areas,have greatly increased the life expectancy of parts.However,residual stress in the process of thermal spray becauses of the larger temperature gradient and differences in physical characteristics between substrate and coating,prone coating to be failured such as fracture,buckling and spalling,delamination. Therefore,there is great significance in study of residual stress within thermal spray coating.Simulation and analysis of residual stress within thermal spray ceramic/metallic coating as a result of temperature changes and differences in material thermal expansion coefficient in thermal spray process by using finite element method.The study includes the residual stress of single spray droplet from the melting temperature high-speed impact carbon afer deposited solidification on the surface of substrate and the effects of substrate's preheating temperature,droplet's collision velocity on residual stress.The effects of coating thickness and add middle layer with different thickness on residual stresses within double-layer coating.The effects of compositional gradient and thickness of coating on the residual stresses within ceramic/metallic graded coating.The amendment of coating internal stress formula which is based on the classical beam bending theory.The results show that raising preheating temperature can reduce the stress level in interface after droplet deposited solidification on the substrate surface,but can not change the distribution of stress,collision velocity has little effect on the stress.tensile radial stress in substrate and compressive radial stress in coating because of coating thermal expansion coefficient is less than that of substrate within ceramic/metallic double coating.Interface is the most weakness region,stress concentration occur in the edge of interface,and the value of maximum stress incrase with increasing the coating thickness.Adding intermediate coating could reduce the value of maximum residual stress.Within ceramic volume fraction by f=x~m exponential of transition from pure metal to pure ceramic graded coating,the tentile radial stress at interface decease because performance differences of the interface between coating and substrate reduce with increasing index m,however,the compssive stress at coating surface increase because the ceramic volume fraction mutation with increasing index m.The location of stress concentration near interface transfer along thickness direction to coating surface with m increasing within coating.Increasing coating thickness leads to largen temperature gradient within coating so that the residual stress increase at interface and decrease at coating surface.The error of coating stress based on the classical beam bending theory increase with increading the ratio of coating to substrate,and reduce the error after amended.