金属粘结层厚度对大气等离子喷涂陶瓷涂层粘结强度的影响

Influence of Metal Bond Coat Thickness on Adhesion Strength of APS Ceramic Coatings

应用于金矿开采业中的球阀在服役过程中由于受颗粒磨损,泥浆侵蚀,涂层粘结力/内聚力或者剪切力不高而发生破坏。修复价格昂贵耐腐蚀合金(CRA)球阀典型的工艺是:对合金基体进行钨极惰性气体保护焊(GTAW),球阀表面打磨,以及利用大气等离子喷涂(APS)技术在球阀表面制备陶瓷热喷涂涂层(TSC)。另一种修复方法是利用机加工使球尺寸减小,然后在陶瓷层下面沉积一层较厚的金属粘结层(MBC)以保证球阀的原始尺寸。本文研究了按照ASTM C633标准检测大气等离子喷涂陶瓷涂层的结合强度是否与超音速火焰喷涂的NiCrMo(哈氏合金)金属粘结层的厚度极限有关。实验所用的基体材料为三种耐腐蚀合金(CRA):钛G12,铬镍铁合金625以及2507双相不锈钢,在这三种基体表面沉积了8种不同厚度的金属粘结层。金属粘结层的厚度分别是:0.0015英寸,0.005英寸,0.015英寸,0.030英寸,0.045英寸,0.060英寸,0.075英寸以及0.090英寸。利用大气等离子喷涂工艺在上述8种不同厚度的金属粘结层表面喷涂厚度为0.015英寸的Cr_2O_3,Cr_2O_3-Al_2O_3和TiO_2这三种陶瓷涂层。对样品做了如下测试:涂层结合强度(ASTM C633)测试,金相显微组织分析(ASTM E1920),涂层孔隙率(ASTM E2109方法 B)测试。

Extreme service ball valves in the Gold mining industry,typically experience service damage byparticulate abrasion,slurry erosion,lack of adhesion/cohesion,or shear.Repair of these expensive corrosionresistant alloy(CRA)balls typically require:GTAW welding of the substrate,grinding the ball surface,andapplying a Ceramic thermal spray coating(TSC)by the Air Plasma Spray(APS)process.An alternative repairmethod is to machine the ball undersize,and put a thicker metal bond coat(MBC)under the Ceramic coating toreestablish original dimensions.This study was performed to determine if the ASTM C633adhesion strength ofan APS Ceramic coating was dependent upon a thickness limit of a high velocity oxygen fuel(HVOF)appliedNiCrMo(Hastelloy)MBC.8thicknesses of the MBC were applied to three CRA substrates:Titanium G12,Inconel625,and2507Duplex SS.The MBC thicknesses were:0.0015in,0.005in,0.015in,0.030in,0.045in,0.060in,0.075in,and0.090in.The following3Ceramic coatings:Cr2O3,Cr2O3-Al2O3,and TiO2,were APS applied0.015in on top of8thicknesses of MBC.The following tests were performed:adhesion strength(ASTM C633),metallography(ASTM E1920),and percent porosity(ASTM E2109Method B).