Investigation On Properties Of Hollow Sphere Cellular Materials Of PM1000Alloy By Powder Metallurgy

PM1000is a Ni-based oxide dispersion strengthened (ODS) superalloy withhigh strength, creep strength and corrosion resistance at high temperature. Hollowsphere cellular materials (HSCMs) of PM1000, as high-temperature and lightstructural materials hold important potential applications on high speed aircraft. Inthe present research, hollow sphere cellular materials of PM1000were prepared bypowder metallurgy. The microstructure was examined using optical microscope (OM)and scanning electron microscope (SEM). The element distribution was studied byenergy spectrum analysis. The phase composition was studied by X-raydiffractomater. And the compression property of the hollow sphere cellular materialsof PM1000was measured by universal testing machine. The research results in thispaper were as follows:The mechanical alloying was carried out using a planetary mill in a argonatmosphere with the mass ratio of ball to powder of10:1. The results showed thatthe higher rotation speed and the longer milling time were taking, the bettermechanical alloying effects can be achieved. The XRD results showed that the bestmechanical alloying effects can be achieved with a combination of stainless steelballs with diameter of20,10and6mm, respectively, rotation speed of400r/min,and milling time of35h. While high rotation speed is not good for preparation offine powder. As milling time increasing, the powder is gradually refined and theaverage size of the alloy powder particles is less than30μm after milling30h, usinga combination of tainless steel balls (10,6and3mm) at a rotation speed of320r/min.The alloy slurry was prepared by mixing PM1000alloy powders with thebinder, polyvinyl alcohol solution. Experimental results indicated that the coatingpropertiy of the alloy slurry is related to the particle size of alloy powders: smallerpowders lead to better coating properties. The liquid-solid ratio should be increasedaccordingly as the concentration of polyvinyl alcohol solution increases,in order tokeep good coating property. Generally, a good coating property can be achieved foralloy powders with average particle size of20.3μm, liquid-solid ratio of20%andconcentration of polyvinyl alcohol solution of3wt.%. With the increase of thedrying temperature, the block structure green dry faster. The best dryingtemperature was70℃, and the dry time is22min.For the sinteing of Hollow sphere cellular materials of PM1000, thetemperature was increased up to350°C with a rate of4°C/min, held for30min, before reaching the final temperature with a rate of12°C/min. The results showedthat the sintering carried out under a carbon reduction condition can prevent alloypowders from oxidation. As a result, the HSCMs have high density and excellentmechanical properties. In the temperature range of1100~1300℃, as the sinteringtemperature increases, the micro-hardness and the compression strength of theHSCMs increases accordingly because of the reduction of the porosity and theincrease of the densification. The micro-vickes’s hardness and the compressiveyield strength of the HSCMs which was sintered under the temperature of1300℃are26.31MPa and195.78MPa respectively. However, when the sinteringtemperature reaches1350℃, the materials melt partially, resulting in structuralimperfection. For this reason,1300℃is the optimal sintering temperature toachieve structurally perfect hollow sphere cellular materials of PM1000withexcellent synthetic properties.