真空熔渗烧结装备开发和实验研究OA

[Objective]Wear-resistant seal coating on the tip of single-crystal turbine blades plays a crucial role in ensuring the airtightness and operational efficiency of aeroengines.With the continuous increase in turbine inlet temperature,the harsh service environment imposes increasingly stringent requirements on the coating,such as superior high-temperature wear resistance,oxidation resistance and adhesion.However,existing preparation technologies face prominent challenges:thermal spraying and laser cladding produce coatings with flat surfaces where abrasive particles are uniformly distributed inside,failing to meet the protruding morphological requirement;electrodeposited yields coatings that suffer from insufficient adhesion and increased brittleness with increasing thickness;brazing,while improving interface bonding,damages the base metal because of the diffusion of melting-point-lowering elements.Additionally,Al2O3 ceramic particles,as ideal reinforcing phases,exhibit poor wettability with metal melts,and their particle size and content significantly affect coating quality,yet relevant systematic research is scarce.To address these issues,this study aims to develop a high-performance preparation technology for NiCoCrAlYTa-Al2O3 blade-tip wear-resistant coatings,synergistically integrating the high-temperature wear resistance of particles and protective performance of the coating while avoiding damage to the single-crystal base metal.[Methods]A visualized high-vacuum infiltration sintering apparatus was developed based on a traditional vacuum tube furnace.Key improvements included equipping a 10×visual window,a high-speed camera(maximum shooting rate of 3 980 frames/s),and a synchronous light source for real-time recording of the entire experimental process,as well as integrating a high-flux diffusion pump,vacuum gauge,and vacuum meter to achieve a high-vacuum environment of 1×10-3 Pa with real-time monitoring.Al2O3 particles with three sizes(1,10,and 30 μm)and five weight percentages(0%,3%,5%,8%,and 10%)were selected as reinforcing phases,NiCoCrAlYTa as the coating matrix,and NiCrSi as the infiltration alloy.Electroless Ni-P alloy plating was applied to Al2O3 particles to improve their wettability with the metal melt.The coating preparation followed a specific thermal cycle:heating to 420℃at 10℃/min for 30 min,subsequent heating to 1 200℃at 10℃/min for 2 h,cooling to 600℃at a rate not exceeding 5℃/min,and final natural cooling to room temperature.The microstructure and surface morphology of the coatings were characterized using precision image measuring instruments,scanning electron microscopy(SEM)equipped with energy dispersive spectroscopy(EDS),and 3D profilometers.Friction and wear tests were conducted on a self-designed rig with a normal load of 1.5 N,sliding speed of 1 m/s,and total sliding distance of 1 000 m;the wear resistance was evaluated by measuring the weight loss of coatings and mating graphite disks.[Results]The electroless Ni-P plating effectively improved the wettability of Al2O3 particles with the metal melt,reducing the contact angle from 93.425° to 80.371°.Particle size had a considerable impact on coating formation:coatings reinforced with 1 and 10 μm Al2O3 particles contained numerous pores due to particle agglomeration,while those with 30 μm Al2O3 particles did not exhibit pore defects,resulting in dense coatings with protruding Al2O3 particles exhibiting an exposure height of 220-240 μm,which met the morphological requirements.Regarding mass percentage,when the Al2O3 content was≤5%,the total coating porosity remained stable at approximately 0.6%with gas pores as the main defects;beyond 5%,particle agglomeration intensified,clogging seepage channels and leading to a sharp increase in porosity(0.56%for the 3%sample and 2.22%for the 10%sample).Friction and wear test results showed that all coatings containing Al2O3 particles exhibited considerably lower wear rates than the coating without Al2O3.The sample with 8%30 μm Al2O3 particles achieved the lowest wear rate of 0.001 51 mg·N-1·m-1,and the mating graphite disks formed effective wear marks with a depth of 60-90 μm,indicating excellent wear resistance and cutting-sealing performance.The main wear mechanism of the coatings was the spallation of protruding Al2O3 particles,and the wear rate increased at 10%Al2O3 content because of excessive particle agglomeration.[Conclusions]This study successfully developed a visualized high-vacuum infiltration sintering apparatus that enables real-time monitoring of the sintering process.The optimal preparation parameters were determined as follows:30 μm Al2O3 particles with a mass percentage of 5%-8%,sintering temperature of 1 200℃,and holding time of 2 h.The NiCoCrAlYTa-Al2O3 coating prepared under these parameters exhibits excellent comprehensive performance,including low porosity,high wear resistance,and strong adhesion without damaging the single-crystal base metal.This technology solves the key technical problems of existing preparation methods and provides important theoretical and experimental support for the engineering application of high-performance wear-resistant seal coatings on single-crystal turbine blade tips.