發(fā)布時間：2018-08-30 11:07

【摘要】：3D打印是增材制造的新發(fā)展,利用3D打印工藝成形金屬構件是機械制造業(yè)的重要發(fā)展方向。激光熔覆及其成形技術是在激光加工技術的基礎上研制成功的一種新的快速成形技術�；诟吣芗す馐娜鄹布夹g既可以用于基體材料的表面改性,又能對表面磨損零件進行修復和金屬構件的成形。激光材料表面改性技術的工藝是一個十分復雜的過程,本文通過對激光熔覆過程溫度場的動態(tài)模擬來預測最優(yōu)工藝參數(shù),采取雙因素全面試驗法對模擬結果進行驗證,并對最優(yōu)工藝參數(shù)和搭接率下的熔覆層進行摩擦磨損檢測。主要研究內(nèi)容如下:(1)建立Q235鋼表面激光熔覆低碳鐵基合金溫度場三維模型,考慮了對流、熱物性參數(shù)、相變潛熱和同步送粉特點等因素,分析了熔覆層頂?shù)c溫度隨時間變化曲線,對熔覆層成形質(zhì)量進行預測,得出:P=2000 W、v=10 mm/s時,熔覆層頂?shù)c最高溫度分別為2300℃和1500℃,有利于得到表面形貌較好、與基體良好冶金結合且稀釋率低的熔覆層。對該參數(shù)下的不同時刻溫度場分布進行分析,看到激光熔覆受熱影響的區(qū)域小,除熔覆剛開始階段,熔池周圍溫度場趨勢穩(wěn)定,熔池最高溫度點位于光斑中心和熔池最深處點之間。(2)在3D打印與激光再制造平臺成套設備上進行激光熔覆鐵基合金的試驗研究。確定激光功率和掃描速度作為變量,對不同工藝參數(shù)組合下熔覆層幾何形狀、宏觀形貌、微觀組織進行檢測和分析,結果表明:熔覆層寬度隨激光功率的增加而增加,而熔覆層厚度隨激光功率的加大呈現(xiàn)雙峰狀;熔覆層寬度和厚度隨著掃描速度的加快而減小。提出了激光線能量密度來說明激光功率和掃描速率的匹配性,對判斷熔覆層表面形貌的連續(xù)性和過燒有重要意義。結合模擬溫度曲線和金相圖片,可知熔覆層熔覆區(qū)為平面晶和垂直于界面的樹枝晶構成,過渡區(qū)為富Gr、Ni的板條狀馬氏體;當P=2000 W、v=10 mm/s時,熔覆區(qū)組織均勻致密,過渡區(qū)中基體和熔覆材料良好冶金結合且稀釋率低,熱影響區(qū)鐵素體與珠光體得到了細化,熔覆層質(zhì)量優(yōu)異。(3)采用單道最優(yōu)工藝參數(shù)和合適的搭接率進行多道熔覆,制備出磨削深淺不同的鐵基合金小試環(huán),在MVF-1A型立式摩擦磨損試驗機上進行等速變載荷、等載荷變速情況下的摩擦磨損試驗,結果表明:隨著載荷的增加,摩擦系數(shù)也增加;隨著轉速的增大,摩擦系數(shù)略微減小。對熔覆層不同深度的顯微硬度進行測量,可知隨著至表面距離的增加,經(jīng)歷緩慢下降、加速下降、緩慢下降三個階段,熔覆區(qū)外層硬度(350 HV)最高且為基體的2倍。磨痕SEM圖片顯示,隨著載荷加大,黏著磨損加劇;熔覆區(qū)磨損機制為磨粒磨損和黏著磨損,過渡區(qū)為剝層磨損、黏著磨損和磨粒磨損。
[Abstract]:3D printing is a new development of material increasing manufacturing. It is an important development direction of mechanical manufacturing to use 3D printing technology to form metal components. Laser cladding and its forming technology is a new rapid prototyping technology developed on the basis of laser processing technology. The cladding technology based on high energy laser beam can be used not only to modify the surface of the matrix material, but also to repair the worn surface parts and to form the metal components. The technology of surface modification of laser material is a very complicated process. In this paper, the optimum process parameters are predicted by dynamic simulation of temperature field in laser cladding process, and the simulation results are verified by two-factor comprehensive test method. The friction and wear of the cladding layer under the optimal process parameters and lap ratio were tested. The main research contents are as follows: (1) the temperature field model of laser cladding low carbon Fe-base alloy on Q235 steel surface is established, and the factors such as convection, thermal physical parameters, latent heat of phase transformation and the characteristics of simultaneous powder feeding are taken into account. The temperature variation curve of the top and bottom point of the cladding layer with time is analyzed, and the forming quality of the cladding layer is predicted. It is concluded that the maximum temperature of the top and bottom point of the cladding coating is 2300 鈩，

本文編號：2212880