Study On Erosion Wear Mechanism Of Tool Materials And Surface Coatings In The Condition Of Fracturing

Fracturing technology is commonly used in the field of oil and gas production, its main function is to increase the channels of oil and gas flow, the permeability of hydrocarbon reservoir will be enhanced and then the production of oil and gas will be promoted. In fracturing process, given the requirements of high fracturing efficiency, high pressure and sand content fracturing technology are used, the erosion wear of string and downhole tools become more and more serious, which may lead to erosion failure and severely affect the normal production of fracturing. To reveal the erosion wear mechanisms, different material was prepared and comprehensive experiments on erosion were conducted in this paper. The corrosion and wear properties of different materials were evaluated, and the material with excellent erosion resistance was found.The29CrMo44with P110grade was adopted as experimental materials, which were quenched at930-940℃and tempered at50℃, whose microstructures were tempered sorbite. The grain size of the materials are level5-8, yield strength870MPa, tensile strength921MPa, hardness21.5HRC, elongation19.5%, and mechanical properties are fine.The laser cladding coatings (LCCs) with the20%Cr,30%Cr and40%Cr were prepared on the P110substrate by laser cladding. The dilution ratios of the LCCs were7%,5%and6%, respectively. The microstructure of the cross-section were planar crystal, swelling crystal and dendrite crystal, and mainly of martensite with few retained austenite with ferrite. The cladding region were mainly for gamma a(Fe,Ni), and too much of Cr with the C element, gradually formed a Cr23C6, Cr7C3etc. The highest hardness of the LCCs (higher than P110) was513HV, and the average hardness were350HV,376HV and462HV, respectively.A Fe-Cr-Mo-Mn-W-B-C-Si master alloy was prepared by induction-melting of high-purity elemental constituents in a copper crucible. The powders were produced by high pressure argon gas atomization. The as-atomized powders were analysed by scanning electron microscope (SEM), transmission electron microscope (TEM) and X ray diffraction (XRD) phase, with the characteristics of completely amorphous and particle sizes in the range of less than45mm. The amorphous metallic coatings (AMCs) with the thickness of200and400μm were prepared by high-velocity oxy-fuel (HVOF) thermal spraying. The coatings present a typical layer structure of uniform chemical composition, which exhibited low porosity of1.25%and1.45%. There exist no evident grain boundaries in AMCs. The composite structure formation of some nanocrystallite phases embedded in the amorphous matrix by TEM. The major crystalline phases were composed of Fe2C, Cr7C3, M23C6, Cr2B, and some oxides by XRD. The micro-hardness of the AMCs were higher than900HV, which the average hardness were828.3HV and713.2HV, respectively.The Fe-based high chromium alloys(FHCs) were designed and prepared by plasma furna ce based on the composition of13Cr Steel. The accurate chemical composition of the prepare d alloys was tested by spectroscope, and the results show the contents are homogeneous whic h meet the design demands and the alloys are among super13Cr series. The SEM observation indicates that the main microstructures are lath martensite, and the grains are fine and branch ed. The phase is mainly composed of martensite and Fe-Cr phase which are proven by XRD. The Vickers hardness of the prepared alloys can reach296HV, which is higher than normal0Crl3.The erosion wear tests were conducted using a self-made jet apparatus for erosion wear. The erosive wear resistance of AMCs, LCCs, FHCs and P110decreased in the order as follows:AMCs>LCCs>FHCs>P110. The AMCs and LCCs exhibited highest erosive wear resistance, which were the optimal materials served in the erosive wear environments. FHCs were suitable for severe corrosive and abrasive environments. The erosive wear mechanism different from each other. The mechanism of the FHCs was brittle deformation, while those of P110, LCCs and FHCs were plastic deformation. The erosive wear behavior of AMCs similar to that of brittle materials, but with a different erosive wear mechanism.