issue to get the custom post type based on custom post type category in wordpress?

I have created the custom post type article and category “Education”.
I wanna to get all the posts of category “Education”, i.e post type article but when I pass category id in query then it does not return any post. If I remove the category id from the query then it returns all the posts of type article.

How can I get the posts based on category that I have created for custom post article.
I am using the following code.

   $args = array(
  'post_type' => 'article',
  'orderby' => 'date',
  'order' => 'ASC',
  'post_status' => 'publish',
  'cat' => '18'


   );
  $query = new WP_Query($args);
  print_r($query);