【摘要】：激光熔覆技術(shù)具有稀釋率低、熱影響區(qū)小、效率高等優(yōu)點(diǎn),將其用于失效模具的修復(fù)有巨大的市場(chǎng)價(jià)值和應(yīng)用前景。在模具表面進(jìn)行激光熔覆可以提高模具的耐熱、耐磨和耐腐蝕性,延長(zhǎng)模具的使用壽命,從而獲得更好的經(jīng)濟(jì)效益。本文基于三維打印中的激光熔融沉積(LMD)技術(shù),采用理論分析和實(shí)驗(yàn)研究相結(jié)合的方法對(duì)激光熔覆的基礎(chǔ)理論、工藝參數(shù)、宏觀和微觀組織性能等方面進(jìn)行了較為深入的研究。本文具體內(nèi)容如下:(1)以球墨鑄鐵為實(shí)驗(yàn)基材,熔覆粉末選用鎳基合金,通過(guò)控制變量的方法,在激光功率密度或掃描速度恒定的條件下,研究工藝參數(shù)(功率1000W-2000W、掃描速度2mm/s-8mm/s)對(duì)熔覆層宏觀及微觀性能的影響。實(shí)驗(yàn)表明,在對(duì)比分析了不同參數(shù)下熔覆層的變化后,選用優(yōu)化后的工藝參數(shù),實(shí)現(xiàn)了對(duì)破損模具的表面修復(fù)。(2 )本文研究了搭接率對(duì)單層多道和多層多道的宏觀容貌和熔覆性能的影響。分析了在激光熔覆的過(guò)程中,搭接率過(guò)大、適中和過(guò)小對(duì)熔覆道造成的三種成型情況。結(jié)果表明,選擇與激光功率、送粉速率和掃描速度等參數(shù)相匹配的搭接率(約33%)有助于更好地實(shí)現(xiàn)多層和多道的熔覆搭接。(3 )通過(guò)金相顯微鏡和硬度計(jì)等儀器對(duì)熔覆層及其截面交界處的微觀組織結(jié)構(gòu)和硬度分布進(jìn)行了深入的研究。分析了熔覆層缺陷的種類及出現(xiàn)的原因,并提出了針對(duì)不同原因?qū)е碌牧鸭y和氣孔的解決方法�；谏鲜鲅芯�,本文采用優(yōu)化后的熔覆參數(shù)在模具上進(jìn)行表面修復(fù),得到了初步的修復(fù)效果。
[Abstract]:Laser cladding technology has the advantages of low dilution rate, small heat affected zone and high efficiency. It has great market value and application prospect in repairing failure mould. Laser cladding on the surface of the mould can improve the heat resistance, wear resistance and corrosion resistance of the mould, prolong the service life of the mould and obtain better economic benefits. Based on the laser fused deposition (LMD) technology in 3D printing, the basic theory and process parameters of laser cladding are studied by combining theoretical analysis with experimental research. Macroscopical and microstructural properties were studied in detail. The main contents of this paper are as follows: (1) with nodular cast iron as the experimental substrate and nickel alloy as the cladding powder, the technological parameters (power 1000W-2000W) are studied under the condition of constant laser power density or scanning speed by controlling variables. The effect of scanning rate 2mm/s-8mm/s) on the macroscopic and microscopic properties of the cladding layer. The experimental results show that, after comparing and analyzing the change of cladding layer under different parameters, the optimized process parameters are selected. The surface repair of the damaged die is realized. (2) the effect of lap ratio on the macroscopic appearance and cladding performance of single layer and multi channel is studied. In the process of laser cladding, three kinds of forming conditions of cladding channel caused by overlapping rate, moderate rate and too small are analyzed. The results show that the selection of laser power, The overlap rate (about 33%) of the parameters such as powder feeding rate and scanning speed is helpful to better realize the multilayer and multichannel cladding. (3) the cladding layer and its cross section junction are obtained by means of metallographic microscope and hardness meter. The microstructure and hardness distribution were studied. The types and causes of defects in cladding layer are analyzed, and the solutions to crack and porosity caused by different reasons are put forward. Based on the above research, the optimized cladding parameters were used to repair the surface of the die, and a preliminary restoration effect was obtained.
【學(xué)位授予單位】：南京師范大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TQ171.68

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