摘要
目的研究超音速火焰喷涂工艺参数对WC-12Ni硬质合金涂层抗冲击性能的影响。方法依据氧气/燃料比(λO/F)调节工艺参数,以λO/F=1.1为基准点,分别固定氧气流量811 L/min、降低煤油流量,或者固定煤油流量22.7 L/h、增大氧气流量,均使λO/F增至1.2和1.3,制备了5组涂层,分析涂层组织及力学性质的变化规律,研究柱-面接触大载荷冲击下的涂层抗冲击行为。结果λO/F对涂层组织及力学性质的影响并非已报道的单调变化规律。固定氧气流量、降低煤油流量使λO/F由1.1增至1.3时,涂层孔隙率由0.91%增至1.24%,硬度和弹性模量分别由10.1、344.0 GPa降至8.6、313.9 GPa;冲击坑体积由2.1×10^(-3)增至3.3×10^(-3)mm^(3),且损伤微观特征由WC颗粒剥落向涂层开裂发展。当固定煤油流量、增加氧气流量使λO/F由1.1增至1.3时,孔隙率降至0.85%,硬度和弹性模量分别增至10.8、382.5 GPa,冲击坑体积增至2.6×10^(-3)mm^(3),直到λO/F=1.3时涂层表面开始出现裂纹。结合涂层硬度和弹性模量分析结果可知,在H3/E2≤8.4 MPa时,涂层发生开裂损伤,裂纹长度随着H3/E2的增加而减小。在H3/E2>8.4 MPa时,涂层损伤以WC颗粒剥落为主,且随着H3/E2的增加而减轻。高H3/E2可提高涂层的抗冲击性能,当H3/E2由6.4 MPa增至8.7 MPa时,坑体积和WC剥落程度分别降低了36%、35%。结论超音速火焰喷涂WC-Ni涂层的H3/E2定量表征了其抵抗塑性变形和开裂的能力,决定了涂层的抗冲击性能。
The principal aim of this work is to study the effect of oxygen-fuel ratio(λO/F)on the impact resistance of high-velocity oxy-fuel(HVOF)sprayed WC-12Ni coatings.The value ofλO/F=1.1 was used as the starting point to adjust the spray process parameters,and theλO/F values were increased to 1.2 and 1.3,which were regulated by reducing the kerosene flow at a fixed oxygen flow of 811 L/min or increasing the oxygen flow at a fixed kerosene flow of 22.7 L/h.The corresponding five groups of WC-12Ni coatings were prepared at the above differentλO/F values.The microstructure,microhardness and elastic modulus of the coatings were analyzed,respectively.The impact behavior resistance of the coatings was studied through a flat-cylinder contact heavy-load impact test.The experimental results indicated that the monotonous relationship between theλO/F value and microstructure and mechanical properties reported in literature was not observed for the WC-12Ni coatings.As theλO/F value increased from 1.1 to 1.3 that was regulated by reducing the kerosene flow at a fixed oxygen flow of 811 L/min,the porosity of the coatings increased from 0.91%to 1.24%,and the microhardness and elastic modulus of the coatings decreased from 10.1 and 344.0 to 8.6 and 313.9 GPa,respectively.In addition,the impact resistance of the coatings was weakened.The crater volume of the coatings increased from 2.1×10^(-3)to 3.3×10^(-3)mm^(3),and the damage features of the coatings changed from WC grains spalling to cracking.When theλO/F value was 1.3,the integral crack length reached the maximum of approximately 54μm.However,the opposite trend of microstructure,microhardness and elastic modulus of the coatings was observed as theλO/F value increased from 1.1 to 1.3 regulated by increasing the oxygen flow at a fixed kerosene flow of 22.7 L/h.Correspondingly,the porosity of the coatings decreased to 0.85%,and their microhardness and elastic modulus increased to 10.8 and 382.5 GPa,respectively.Moreover,when theλO/F value was 1.2,the crater volume of the coatings increased to 2.4×10^(-3)mm^(3),and the coating damage behavior was still the WC grains spalling but with increased spallation as compared with that ofλO/F=1.1.Continuing to increase theλO/F value to 1.3,the crater volume reached 2.6×10^(-3)mm^(3),and the cracking damage of the coatings occurred with the integral crack length of about 30μm.By combining the analysis of microhardness and elastic modulus of the coatings,the relationship between the impact damage behavior and H3/E2 of the coatings was determined.Namely,the impact resistance of the coatings was improved with the increase of H3/E2.When H3/E2 was not higher than 8.4 MPa(λO/F=1.3;O 998 L/min,F 22.7 L/h),the surface cracking occurred,and the integral crack length decreased with the increase of H3/E2.When exceeding that value,the main damage feature of the coatings was the WC spalling,and the WC spallation degree reduced with the increase of H3/E2.As H3/E2 increased from 6.4(λO/F=1.3;O 811 L/min,F 18.4 L/h)to 8.7 MPa(λO/F=1.1),the crater volume and degree of WC spalling was reduced by 36%and 35%,respectively.The ability to resist plastic deformation and cracking of coatings is quantitatively characterized by H3/E2 of HVOF sprayed WC-Ni coatings,which determines the impact resistance of the coatings.
作者
张书姣
朱小鹏
苑菁茹
奚恒恒
雷明凯
ZHANG Shujiao;ZHU Xiaopeng;YUAN Jingru;XI Hengheng;LEI Mingkai(School of Materials Science and Engineering,Dalian University of Technology,Liaoning Dalian 116024,China)
出处
《表面技术》
EI
CAS
CSCD
北大核心
2024年第19期193-200,222,共9页
Surface Technology
基金
国家自然科学基金面上项目(52371054,U21B2078)。
关键词
超音速火焰喷涂
氧气/燃料比
WC-Ni涂层
力学性能
抗冲击性能
high-velocity oxy-fuel(HVOF)thermal spray
oxygen-fuel ratio
WC-Ni coating
mechanical properties
impact resistance
